Clement Rasul

Printer Sharing on Ubuntu 10.10

2011-07-08T18:54:00.001-07:00

Set the Linux Printer Server

The procedure below is tested on Linux Printer Server running Ubuntu 10.10 and CUPS 1.4.4. To setup the Linux Printer Server, make sure that the server can print into the connected printer. Once this is done, you can enable print sharing.

a) Click on System -> Administration -> Printing
b) Click on Add Printer and select your printer on the listed items
c) Afterwards, test if you can print from your server.

d) Enable print sharing by right-clicking on the printer and selecting "Properties" menu.
e) On the Policies, check the State "Enabled, Accepting jobs, and Shared"
f) Under access control select the button "Deny printing for everyone except these users:", then type in the list of users you want to share printer and click on the "Add" button. (e.g., bisita - this should be equivalent to the user logged in on the client machine)
g) Click on the button "Apply" then "OK"
h) On the "Printer Configuration" window, select the Server->Settings menu.
i) Check the item "Publish shared printers connected to this system", and "Allow printing from the Internet", then click on the OK button.
j) Restart the cups daemon by typing on the terminal:

# /etc/init.d/cups restart

On a Linux Client Machine

a) Click on System->Administration->Printing
b) Click on the Add button
c) Under the "Network Printer", select "Internet Printing Protocol"
d) Under the Host field, type in the IP address of the printer server (e.g., 192.168.1.10)
e) Under the Queue field, type in the name of the printer after the prefix /printers/ (e.g., /printers/hp900)
f) Click the button to "Verify" to confirm if your settings are good.
g) Then click the "Forward" button and select your printer on the listed items
h) Type in a description of your printer (e.g., hp900)
i) Finalized the setup by clicking the "Apply" and "OK" button

If everything goes smoothly, you should be able to print from your Linux client machine to your Linux Printer Server.

Windows Printing Thru CUPS

Windows can print to a Linux Print Server running cups. I assume that the CUPS server has been properly installed on a Linux server and it has been set as "sharing". The following procedure is how to set the printer under Windows (I have tested it under Windows XP Home Edition but my guess is it should work on most Windows variants):

a) Add Printer
b) Select "Connect Printer to the Internet"
c) Type in the address of CUPS server and the print queue (e.g., http://192.168.1.117:631/printers/hp900)
d) When prompted for the printer type, select "Generic", then select "MS Publisher Imagesetter" (This is usually a built in driver on Windows)

That's it.

Test your printing. You can monitor the status of your printing by going to your browser and typing the address (e.g., http://192.168.1.117:631) and clicking on the "Jobs" menu.

Erratum: The above procedure does not work with Windows 7 Starter Edition.

Printer Sharing via LPD

Print Sharing thru the legacy LPD is implemented via the cups-lpd daemon. This is activated through the xinetd superserver daemon. The procedure are as follows:

a) On the Linux Printer Server, download the xinetd superserver daemon xinetd by typing the command on the terminal:

# apt-get install xinetd

b) Configure the xinetd daemon by typing creating the a (e.g., printer ) under the directory /etc/xinetd.d/ and typing the following settings:

service printer
{
socket_type = stream
protocol = tcp
wait = no
user = bisita
group = sys
server = /usr/lib/cups/daemon/cups-lpd
server_args = -o document-format=application/octet/stream
}

c) Start the xinetd server by typing the command:

# /etc/init.d/xinetd start

d) Create the file hosts.lpd under the directory /etc and type in the name of allowed hosts (e.g., mydesktop ). Be sure the hostname mydesktop can be properly identified in the network. If not, include the name under the hosts file.

Printer Sharing under SMB protocol

The procedure below assumes that you have done the above procedure on Printer Sharing via LPD. The reason for this is that the Samba Server setup here for printing relies on the bsd as the printing mode.

a) Download and install the Samba software in the server.

# apt-get install samba

b) Configure the Samba server by editing the file /etc/samba/smb.conf given the pattern below:

[global]
workgroup = RASUL
netbios name = TIKBALANG
passdb backend = tdbsam

printcap name = cups
printing = bsd
load printers = yes

[printers]
comment = All Printers
browseable = yes
security = share
use client driver = yes
guest ok = yes
path = /var/spool/smbprint
printable = yes
public = yes
writable = yes
create mode = 0700

c) Create the directory /var/spool/smprint and change the ownership to 777 mode.

# mkdir /var/spool/smbprint
# chmod 777 /var/spool/smbprint

d) Restart the Samba server as follows:

#/etc/init.d/nmbd restart
#/etc/init.d/smbd restart

Afterwards, test if you can print from a Windows or Linux client machine.

Setting the Network Card to Static IP on Ubuntu

2011-07-01T21:16:00.000-07:00

Edit the /etc/network/interaces file to:

auto eth1

iface eth1 inet static

address 10.10.10.2

netmask 255.255.255.0

gateway 10.10.10.1

Sample smb.conf File

2011-06-29T08:15:00.000-07:00

[global]
netbios name = KAPRE
workgroup = HEDCEN
server string = HedCen File Server
security = user
guest account = bisita

[teachers]
path = /home/teacher/Documents
writeable = yes
valid users = @teacher
locking = yes
create mode = 0660
directory mode = 0770

[students]
path = /home/student/Documents
writeable = yes
valid users = @student
locking = yes
create mode = 0660
directory mode = 0770

[home]
comment = Home Directory
path = %H
valid users = %S
create mode = 0600
directory mode = 0700
locking = no

HedCen Squid Server

2011-06-17T22:40:00.000-07:00

acl all src all
acl manager proto cache_object
acl localhost src 127.0.0.1/32
acl to_localhost dst 127.0.0.0/8 0.0.0.0/32
acl localnet src 10.0.0.0/8 # RFC1918 possible internal network
acl localnet src 172.16.0.0/12 # RFC1918 possible internal network
acl localnet src 192.168.0.0/16 # RFC1918 possible internal network

acl blocksites url_regex "/etc/squid/block-squid.acl"
acl blocktime url_regex "/etc/squid/timeblock-squid.acl"

acl morning time 07:00-12:00
acl okam1 time 00:00-06:59
acl okam2 time 12:01-12:29
acl afternoon time 12:30-19:00
acl okpm1 time 19:01-23:59

acl SSL_ports port 443
acl Safe_ports port 80 # http
acl Safe_ports port 21 # ftp
acl Safe_ports port 443 # https
acl Safe_ports port 70 # gopher
acl Safe_ports port 210 # wais
acl Safe_ports port 1025-65535 # unregistered ports
acl Safe_ports port 280 # http-mgmt
acl Safe_ports port 488 # gss-http
acl Safe_ports port 591 # filemaker
acl Safe_ports port 777 # multiling http
acl CONNECT method CONNECT

http_access deny blocksites

http_access deny morning blocktime
http_access deny afternoon blocktime

http_access allow okam1 blocktime
http_access allow okam2 blocktime
http_access allow okpm1 blocktime

http_access allow manager localhost
http_access deny manager
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localnet
http_access allow localhost
http_access deny all
icp_access allow localnet
icp_access deny all

http_port 3128 transparent

hierarchy_stoplist cgi-bin ?
access_log /var/log/squid/access.log squid
refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440
refresh_pattern -i (/cgi-bin/|\?) 0 0% 0
refresh_pattern . 0 20% 4320
acl shoutcast rep_header X-HTTP09-First-Line ^ICY.[0-9]
upgrade_http0.9 deny shoutcast
acl apache rep_header Server ^Apache
broken_vary_encoding allow apache
coredump_dir /var/spool/squid

HedCen DHCP Server

2011-06-17T22:39:00.000-07:00

#
# DHCP Server Configuration file.
# see /usr/share/doc/dhcp*/dhcpd.conf.sample
#
ddns-update-style interim;
ignore client-updates;

subnet 10.10.10.0 netmask 255.255.255.0 {
range 10.10.10.10 10.10.10.110;
option routers 10.10.10.1;
option subnet-mask 255.255.255.0;
option domain-name "hedcen.portal.ph";
option domain-name-servers 10.10.10.1;
option netbios-name-servers 10.10.10.1;
default-lease-time 21600;
max-lease-time 43200;
}

Transparent Squid Setup Firewall Script

2011-06-17T22:37:00.000-07:00

#!/bin/bash

echo 1 > /proc/sys/net/ipv4/ip_forward

# Flush rules
iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X

iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 3128
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 3128
iptables -t nat -A POSTROUTING -s 10.10.10.0/255.255.255.0 -d 0.0.0.0/0.0.0.0 -j MASQUERADE

Sample Squid Configuration File

2011-06-02T09:03:00.000-07:00

The following is a sample squid 2.7 configuration file (/etc/squid/squid.conf):

acl all src all
acl manager proto cache_object
acl localhost src 127.0.0.1/32
acl to_localhost dst 127.0.0.0/8 0.0.0.0/32
acl localnet src 10.0.0.0/8 # RFC1918 possible internal network
acl localnet src 172.16.0.0/12 # RFC1918 possible internal network
acl localnet src 192.168.0.0/16 # RFC1918 possible internal network

acl blocksites url_regex "/etc/squid/squid-block.acl"

acl officehour time M T W H F 9:00-16:59
acl afteroffice time 17:00-24:00
acl beforeoffice time 00:00-6:00
acl banned dst www.pornsite.com

acl SSL_ports port 443 # https
acl SSL_ports port 563 # snews
acl SSL_ports port 873 # rsync
acl Safe_ports port 80 # http
acl Safe_ports port 21 # ftp
acl Safe_ports port 443 # https
acl Safe_ports port 70 # gopher
acl Safe_ports port 210 # wais
acl Safe_ports port 1025-65535 # unregistered ports
acl Safe_ports port 280 # http-mgmt
acl Safe_ports port 488 # gss-http
acl Safe_ports port 591 # filemaker
acl Safe_ports port 777 # multiling http
acl Safe_ports port 631 # cups
acl Safe_ports port 873 # rsync
acl Safe_ports port 901 # SWAT
acl purge method PURGE
acl CONNECT method CONNECT

http_access allow afteroffice blocksites
http_access allow beforeoffice blocksites
http_access deny blocksites

http_access deny banned

http_access allow manager localhost
http_access deny manager
http_access allow purge localhost
http_access deny purge
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localhost
http_access deny all
icp_access allow localnet
icp_access deny all
http_port 3128
hierarchy_stoplist cgi-bin ?
access_log /var/log/squid/access.log squid
refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440
refresh_pattern -i (/cgi-bin/|\?) 0 0% 0
refresh_pattern (Release|Package(.gz)*)$ 0 20% 2880
refresh_pattern . 0 20% 4320
acl shoutcast rep_header X-HTTP09-First-Line ^ICY.[0-9]
upgrade_http0.9 deny shoutcast
acl apache rep_header Server ^Apache
broken_vary_encoding allow apache
extension_methods REPORT MERGE MKACTIVITY CHECKOUT
hosts_file /etc/hosts
coredump_dir /var/spool/squid

Installing Windows Fonts on Ubuntu Linux

2011-05-28T04:45:00.000-07:00

There are three (3) ways to install Windows fonts on Ubuntu Linux. I have tested the following procedure under Ubuntu 10.10 Linux distribution but my guess is it should also work on other Linux distributions as well.

Way No. 1

(1) Access the Linux terminal by accessing the menu, Applications->Accessories->Terminal
(2) On the terminal, you have to be user "root" to install the package. To become "root", issue the command:

$ sudo su

This will prompt you for your password. Type in your password. If you are "root", the prompt should change from $ to #.

(3) To download and install the Windows fonts, type the command:

# apt-get install ttf-mscorefonts-installer

(4) To load the fonts, type the command:

# fc-cache -f -v

I am assuming that your computer is connected to the Internet and therefore by issuing the above-mentioned commands, installation of the fonts becomes trivial. As far as I know, you can also use the "Ubuntu Software Center" (click Applications->Ubuntu Software Center) and look for the MS True Type Fonts package.

If you are curious as to where the fonts are located, Ubuntu Linux copies the fonts to the directory "/usr/share/fonts". This directory is only accessible to the "root" user.

Way No. 2

In way 2, we will be installing fonts by manually copying the Windows fonts files and pasting it in the Ubuntu Linux directory.

(1) Copy the Windows fonts in your computer and place it in a transferable media such as a USB stick or CD.
(2) On the Ubuntu Linux computer, access the default home directory by going to "Places->Home Folder". On the home folder, check the "Show Hidden Files" on the "View" menu.
(3) Create the folder ".fonts". Yes, the folder got a dot before the word fonts. On Linux, folders with beginning dots means hidden folders.
(4) Copy the Windows fonts to the ".fonts" folder.
(5) Load the fonts by issuing the command:

$ fc-cache -f -v

As you can see, you don't need to be a "root" user to do this procedure. The fonts however will only be applied to the current user but not system wide unlike Way 1 procedure.

Way No. 3

In way 3, the procedure involves making the fonts available system-wide.

(1) On the terminal, become "root" by issuing the command:

$ sudo su

(2) Access the file manager in root mode by issuing the command:

# nautilus&

The file manager is called nautilus. The & makes the program independent of the terminal where it is run.

(3) Since you are already on the graphical file manager as "root", copy the Windows fonts to the Ubuntu Linux directory "/usr/share/fonts". I suggest creating a separate folder under this like "msttcorefonts".

(4) Load the fonts by issuing the command in the terminal:

# fc-cache -f -v

Other fonts can also be installed on Linux by following way 2 and 3 procedure above.

By the way, if you are concerned about licensing, the Microsoft Core fonts I have mentioned above can be redistributed freely as depicted in its license terms.

Formula for the Intercept and Slope

2010-08-12T18:22:00.001-07:00

Given a two (2) variable equation of a straight line, the formula for the slope is:

Slope (b) = S xy / S x^2

where:

S = summation

x = X minus the Mean of X

y = Y minus the Mean of Y

The formula for the intercept at its point of origin is:

Intercept (a) = M Y - b (M X)

where:

M = arithmetic mean

M Y = Mean of Y

b = Slope

M X = Mean of X

Getting the Square Root and Cube Root

2010-06-14T22:50:00.000-07:00

The OpenOffice Calc spreadsheet formula for square root is:

= sqrt ( A )

Where A = data

This can also be reformulated as:

= A^(1/2)

This reformulation is versatile as it can be extended to handle cube roots as follows:

= A^(1/3)

Harmonic Mean

2010-06-14T22:41:00.000-07:00

The Harmonic Mean formula is:

HM = 1.5 / (0.5/A + 0.5/B + 0.5/C )

Where: A, B, and C = sample data
0.5 is the assigned weight for each sample
1.5 is the total assigned weight for all samples

Given only two samples, the formula becomes:

HM = 1 / ( 0.5/A + 0.5/B )

The manual calculation of Harmonic Mean becomes tedious as the number of samples increases.

OpenOffice Calc spreadsheet uses the following formula in calculating for the Harmonic Mean:

= harmean ( range of cells of the sample data )

Geometric Mean Formula

2010-06-14T22:34:00.000-07:00

The geometric mean formula is:

GM = ( A * B * C ) ^ (1 / n )

Where: A, B, and C = sample data
n = is the number of samples, in this case 3

If there are only 2 sample data, the formula becomes:

GM = ( A * B ) ^ (1/2)

The calculation of the Geometric Mean becomes tedious as soon as the number of samples increases. Fortunately, modern spreadsheets can easily calculate this measure of central tendency. The OpenOffice formula for the Geometric Mean is:

=geomean( range of cells of the sample data )

What is omserv running on port 764?

2009-10-02T06:41:00.000-07:00

There is not much information on omserv running on port 764. By doing trial and error and using the lsof command, I found that omserv is actually nfslock. If you want to turn off this service (I surely do, since I don't know and use this service), issue the command:

chkconfig --levels 2345 nfslock off

This will remove the autoexecute of the nfslock. Afterwards, issue the command to stop the process:

/etc/rc.d/init.d/nfslock stop

To verify if you have stopped the service, type the command:

nmap localhost

Installing Squid as a Service

2009-08-03T08:47:00.000-07:00

To install the Squid Proxy Cache Server as a service under Windows, issue the command:

c:\squid\sbin\>squid.exe -f c:\squid\etc\squid.conf -i -n Squid

The name of the service is "Squid". To verify, type the command "services.msc" and look up the name of "Squid" under the name services column.

Installing PostgreSQL as a Service

2009-08-03T08:43:00.000-07:00

To install the PostgreSQL database as a Service under Windows, issue the command the the PostgreSQL directory as follows:

c:\pgsql\bin> pg_ctl -D c:\pgsql\data register -N PostgreSQL

In the above example, PostgreSQL is the name of the PostgreSQL service. Type the command "services.msc" to verify the name "PostgreSQL".

Sample Size Formula

2009-07-19T20:13:00.000-07:00

If you are at a lost as to how to determine your sample size, I suggest you use Taro Yamane's formula:

n = N /[1+N(e)^2]

where:

n = sample size
N = population size (the universe)
e = sampling error (usually .10, .05 and .01 acceptable error)
^ = raised to the power of

Blocking Sites Using Squid

2009-07-19T08:18:00.000-07:00

Steps


1.  Edit the squid.conf configuration file and add the following lines:

acl blocksites url_regex "c:\squid\etc\squid-block.acl"
http_access deny blocksites

2.  Create the file "squid-block.acl" with the following pattern:

.playboy.com
.friendster.com
.facebook.com
porn
pornstars

This will block the sites with URL playboy.com, friendster.com, facebook.com and
pages with "porn" or "pornstars" entries.

3.  Restart squid

Compiling and Running Squid on Windows

2009-07-18T23:05:00.000-07:00

The following compilation procedure has been tested on MS Windows XP Professional using Squid 3.0 STABLE 16, MinGW 5.1.4 and MSYS 1.0.11.rc-1, ActivePerl 5.1.

Steps

1. Download MinGW and MSYS from http://www.mingw.org
2. Download Squid source code from http://www.squid-cache.org
3. Download the Perl installer from http://www.activestate.com/activeperl/
4. Install MinGW under the directory c:\mingw
5. Install MSYS under the directory c:\msys. Indicate where mingw is located when prompted by MSYS.

6. Add the path to Windows for the following directories:

c:\msys\1.0\bin
c:\msys\1.0\mingw\bin
c:\msys\1.0\mingw\sbin
c:\mingw\bin

This is done by going to "Start->Settings->Control Panel->System icon->Advanced tab->Environment Variables button". Then under the "System Variables" grouping, Select the "Path" and choose "Edit" button. Add the above directories at the end by delimiting it with a semi-colon (;).

8. Unpack the Squid source code and copy it to the directory c:\msys\1.0\home\{username}\squid.

The source code is in tar.gz format. You can use the 7zip software from http://www.7-zip.org to unpack the source code.

9. At the MSYS terminal, go to the Squid source code directory and run the compile commands as follows:

$ cd /home/{username}/squid
$ ./configure --prefix=/usr/local/squid --enable-win32-service
$ make all
$ make install

This will create the Squid binaries in the following directory c:\msys\1.0\local\squid

10. You can now copy the folder of Squid binaries to your desired location like "c:\squid" or create an installer package for your other machines.

The MinGW and MSYS software are not needed by Squid once you are able to create its binaries under Windows.

11. Assuming that you have relocated the Squid binaries to c:\squid, edit the squid.conf configuration file to reflect the relative references to the file locations under Windows.

12. Initialize the cache by issuing the command:

c:\squid\sbin> squid.exe -z

The will create the cache folders and files under c:\squid\var\cache

13. Start the Squid server by issuing the command:

c:\squid\sbin\squid -f c:\squid\etc\squid.conf

This will start Squid and will load the configuration file squid.conf under the directory c:\squid\etc.

Initializing, Starting, Stopping, and Accessing the PostgreSQL Server on Windows

2009-07-12T02:51:00.001-07:00

This assumes that you have the PostgreSQL binaries for Windows and that you have placed it at "c:\pgsql" directory. To set up PostgreSQL, copy the "libpq.dll" file located in the directory "c:\pgsql\lib" to the "c:\windows\system32" directory as follows:

c:\pgsql\lib> copy libpq.dll c:\windows\system32

To initialize the database, create the data directory and initialize it by issuing the "initdb" command in the "c:\pgsql\bin" directory as follows:

c:\pgsql\bin>mkdir c:\pgsql\data
c:\pgsql\bin>initdb -D "c:\pgsql\data"

To start the database, type the "pg_ctl" command as follows:

c:\pgsql\bin> pg_ctl -D "c:\pgsql\data" -l logfile start

This will start the PostgreSQL database and create the database log file "logfile".

To stop the database, type the "pg_ctl" command as follows:

c:\pgsql\bin> pg_ctl -D "c:\pgsql\data" stop

To access the database at the DOS command prompt on Windows, type the command:

c:\pgsql\bin> cmd.exe /c chcp 1252
c:\pgsql\bin> psql

Compiling PostgreSQL on Windows

2009-07-12T02:51:00.000-07:00

The following compilation procedure has been tested on MS Windows XP Professional using PostgreSQL 8.4.0, MinGW 5.1.4 and MSYS 1.0.11.rc-1.

Steps

1. Download MinGW and MSYS from http://www.mingw.org
2. Download PostgreSQL source code from http://www.postgresql.org
3. Download the zlib compression library from http://www.zlib.org
4. Install MinGW under the directory c:\mingw
5. Install MSYS under the directory c:\msys. Indicate where mingw is located when prompted by MSYS.

6. Add the path to Windows for the following directories:

c:\msys\1.0\bin
c:\msys\1.0\mingw\bin
c:\msys\1.0\mingw\sbin
c:\mingw\bin

This is done by going to "Start->Settings->Control Panel->System icon->Advanced tab->Environment Variables button". Then under the "System Variables" grouping, Select the "Path" and choose "Edit" button. Add the above directories at the end by delimiting it with a semi-colon (;).

7. Install the zlib library:

a) Unpack the zlib in MSYS (c:\msys\home\{username}\zlib)
b) Run MSYS by typing the msys.bat file in c:\msys\1.0
c) At the MSYS terminal, type the following:

$ cd /home/{username}/zlib
$ make -f win32/Makefile.gcc

d) Copy the zlib1.dll to c:\mingw\bin
e) Copy the libzdll.a and libz.a to c:\mingw\lib
f) Copy the zlib.h and zconf.h to c:\mingw\include

8. Unpack the PostgreSQL source code and copy it to the directory c:\msys\1.0\home\{username}\postgresql.

The source code is in tar.gz format. You can use the 7zip software from http://www.7-zip.org to unpack the source code.

9. At the MSYS terminal, go to the PostgreSQL source code directory and run the compile commands as follows:

$ cd /home/{username}/postgresql
$ ./configure
$ make
$ make install

This will create the PostgreSQL binaries in the following directory c:\msys\1.0\local\pgsql

10. Create the default data directory for PostgreSQL as "c:\msys\1.0\local\pgsql\data"

11. You can now copy the folder of PostgreSQL binaries to your desired location like "c:\pgsql" or create an installer package for your other machines.

The MinGW and MSYS software are not needed by PostgreSQL once you are able to create its binaries under Windows.

Web-based Administration of PostgreSQL

2009-06-29T01:34:00.000-07:00

The web-based administration tool for PostgreSQL is the "phppgadmin" software. The software is freely downloadable at the "http://phppgadmin.sourceforge.net" website.

To install the phppgadmin on Ubuntu 9.04, issue the command:

# apt-get install phppgadmin

Afterwards, the phppgadmin is now accessible using the browser at the localhost address of "http://localhost/phppgadmin".

Common Problem

1. You cannot access the database using the "postgres" user.

Solution:

login as postgres user and create another administrator user as follows:

# su postgres
$ psql
$ createuser myadmin

When prompted if the user will be "administrator", choose "yes" as follows:

postgres@asus:/home/clemrasul$ createuser
Enter name of role to add: myadmin
Shall the new role be a superuser? (y/n) y

Then, use the new administrator username and password to login into the phppgadmin web interface.

GUI Administration of PostgreSQL

2009-06-29T01:25:00.000-07:00

The graphical user interface (GUI) administration tool for PostgreSQL is "pgadmin". To install "pgadmin" on Ubuntu 9.04, issue the command:

#apt-get install pgadmin3

This will install the "pgadmin" software under "Applications -> Programming -> PgAdmin III".

Accessing PostgreSQL on CLI

2009-06-29T01:07:00.000-07:00

The command line interface (CLI) of PostgreSQL is called "psql". To access the PostgreSQL server, issue the following commands:

# su postgres
$ psql

The first command is to shift from the "root" user to the "postgres" user. PostgreSQL does not allow "root" login. Instead, it uses the "postgres" user as the default administrator of the system.

The second command is to invoke the "psql" CLI under the user "postgres".

The following is the screen example of the above-mentioned command.

root@asus:/etc/init.d# su postgres
postgres@asus:/etc/init.d$ psql
Welcome to psql 8.3.7, the PostgreSQL interactive terminal.

Type: \copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit

postgres=#

Given the psql, you can now create databases and users.

Installing PostgreSQL on Ubuntu

2009-06-29T00:43:00.000-07:00

What is PostgreSQL?

PostgreSQL is a production-grade multi-platform SQL database system. The database system is ANSI SQL92/99 compliant. The software is freely downloadable at http://www.postgresql.org website and is licensed under the BSD open source license.

Installation

To install PosgreSQL on Ubuntu 9.04, issue the command:

# apt-get install postgresql

To start PostgreSQL, issue the command:

#/etc/init.d/postgresql-8.3 start

To restart PostgreSQL, issue the command:

#/etc/init.d/postgresql-8.3 restart

To stop PostgreSQL, issue the command:

#/etc/init.d/postgresql-8.3 stop

More Notes

a) Default port of PostgreSQL is "5342"
b) Default database administrator username is "postgres"
c) Default database template is "template1"

Limits

According to the PostgreSQL website, the following are PostgreSQL 8.3 limits:

Limit	Value
Maximum Database Size	Unlimited
Maximum Table Size	32 TB
Maximum Row Size	1.6 TB
Maximum Field Size	1 GB
Maximum Rows per Table	Unlimited
Maximum Columns per Table	250 - 1600 depending on column types
Maximum Indexes per Table	Unlimited

License Text

License

PostgreSQL is released under the BSD license.

PostgreSQL Database Management System
(formerly known as Postgres, then as Postgres95)

Portions Copyright (c) 1996-2008, The PostgreSQL Global Development Group

Portions Copyright (c) 1994, The Regents of the University of California

Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies.

IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

Restricting Access of Local Users to SSHD

2009-06-24T05:58:00.000-07:00

How to restrict access of local users to the OpenSSH services?

Step 1: Assuming you want to restrict the user "myfriend", edit the "/etc/ssh/sshd_config" file:

# vi /etc/ssh/sshd_config

Step 2: Insert the following line in the file:

DenyUsers myfriend

Step 3: Save and restart your SSH server:

# /etc/rc.d/init.d/sshd restart

Tested

I have tested the above procedure on CentOS 5.3 with OpenSSH as the SSH server software.

Furthermore

(a) For two or more users, the format of the "DenyUsers" directive is as follows:

DenyUsers user1 user2 user3 user4

(b) To restrict groups, the directive is "DenyGroups". The format is as follows:

DenyGroups group1 group2 group3 group4

Installing DenyHosts

2009-06-22T17:38:00.000-07:00

What is DenyHosts?

DenyHosts is a small python program created by Phil Schwartz which is intended to stop SSH attacks by adding an entry to the /etc/hosts.deny file on UNIX/LINUX systems based on the number of failed logins.

Software License

The program is licensed under the General Public License (GPL) version 2.

Download

The program can be downloaded from http://denyhosts.sourceforge.net/

Installing DenyHosts

Using an rpm package of DenyHost, issue the command as "root" user:

# rpm -Uvh DenyHosts-2.6-python2.4.noarch.rpm

DenyHost Files

/usr/bin/denyhosts.py
/usr/lib/python2.4/site-packages/DenyHosts/__init__.py
/usr/lib/python2.4/site-packages/DenyHosts/__init__.pyc
/usr/lib/python2.4/site-packages/DenyHosts/allowedhosts.py
/usr/lib/python2.4/site-packages/DenyHosts/allowedhosts.pyc
/usr/lib/python2.4/site-packages/DenyHosts/constants.py
/usr/lib/python2.4/site-packages/DenyHosts/constants.pyc
/usr/lib/python2.4/site-packages/DenyHosts/counter.py
/usr/lib/python2.4/site-packages/DenyHosts/counter.pyc
/usr/lib/python2.4/site-packages/DenyHosts/daemon.py
/usr/lib/python2.4/site-packages/DenyHosts/daemon.pyc
/usr/lib/python2.4/site-packages/DenyHosts/deny_hosts.py
/usr/lib/python2.4/site-packages/DenyHosts/deny_hosts.pyc
/usr/lib/python2.4/site-packages/DenyHosts/denyfileutil.py
/usr/lib/python2.4/site-packages/DenyHosts/denyfileutil.pyc
/usr/lib/python2.4/site-packages/DenyHosts/filetracker.py
/usr/lib/python2.4/site-packages/DenyHosts/filetracker.pyc
/usr/lib/python2.4/site-packages/DenyHosts/lockfile.py
/usr/lib/python2.4/site-packages/DenyHosts/lockfile.pyc
/usr/lib/python2.4/site-packages/DenyHosts/loginattempt.py
/usr/lib/python2.4/site-packages/DenyHosts/loginattempt.pyc
/usr/lib/python2.4/site-packages/DenyHosts/old-daemon.py
/usr/lib/python2.4/site-packages/DenyHosts/old-daemon.pyc
/usr/lib/python2.4/site-packages/DenyHosts/plugin.py
/usr/lib/python2.4/site-packages/DenyHosts/plugin.pyc
/usr/lib/python2.4/site-packages/DenyHosts/prefs.py
/usr/lib/python2.4/site-packages/DenyHosts/prefs.pyc
/usr/lib/python2.4/site-packages/DenyHosts/purgecounter.py
/usr/lib/python2.4/site-packages/DenyHosts/purgecounter.pyc
/usr/lib/python2.4/site-packages/DenyHosts/python_version.py
/usr/lib/python2.4/site-packages/DenyHosts/python_version.pyc
/usr/lib/python2.4/site-packages/DenyHosts/regex.py
/usr/lib/python2.4/site-packages/DenyHosts/regex.pyc
/usr/lib/python2.4/site-packages/DenyHosts/report.py
/usr/lib/python2.4/site-packages/DenyHosts/report.pyc
/usr/lib/python2.4/site-packages/DenyHosts/restricted.py
/usr/lib/python2.4/site-packages/DenyHosts/restricted.pyc
/usr/lib/python2.4/site-packages/DenyHosts/sync.py
/usr/lib/python2.4/site-packages/DenyHosts/sync.pyc
/usr/lib/python2.4/site-packages/DenyHosts/util.py
/usr/lib/python2.4/site-packages/DenyHosts/util.pyc
/usr/lib/python2.4/site-packages/DenyHosts/version.py
/usr/lib/python2.4/site-packages/DenyHosts/version.pyc
/usr/share/denyhosts/CHANGELOG.txt
/usr/share/denyhosts/LICENSE.txt
/usr/share/denyhosts/README.txt
/usr/share/denyhosts/daemon-control-dist
/usr/share/denyhosts/denyhosts.cfg-dist
/usr/share/denyhosts/plugins/README.contrib
/usr/share/denyhosts/plugins/shorewall_allow.sh
/usr/share/denyhosts/plugins/shorewall_deny.sh
/usr/share/denyhosts/plugins/test_deny.py
/usr/share/denyhosts/scripts/restricted_from_invalid.py
/usr/share/denyhosts/scripts/restricted_from_passwd.py
/usr/share/denyhosts/setup.py

Tested

The installation of the program is fairly easy. I have tested it under CentOS 5.3 with Python 2.4 installation.

Installation Instruction

Read the README.txt file. The README.txt files contains a clear installation instruction for the program. This file is reproduced below:

DenyHosts is a utility developed by Phil Schwartz which aims to
thwart sshd (ssh server) brute force attacks.

Please refer to http://www.denyhosts.net/faq.html

INSTALLATION:
=============

SOURCE DISTRIBUTION
===================

If you downloaded the source distribution file (DenyHosts-#.#.#-tar.gz)
then:

$ tar zxvf DenyHosts-#.#.#-tar.gz (Where #.#.# is the version)

$ cd DenyHosts-#.#.#

as root:

# python setup.py install

This will install the DenyHosts modules into python's site-packages
directory.

BINARY DISTRIBUTION (rpm, deb, etc)
===================

It is assumed that you are familiar with installing a binary package
on your particular operating system. If you are unsure how to do
this, you may wish to install from souce instead.

ALL DISTRIBUTIONS
=================

Once you have installed DenyHosts, by default the directory
/usr/share/denyhosts will be created and a sample configuration
file will be copied into it. A sample daemon-control script will
also be copied into the /usr/share/denyhosts directory.

DenyHosts requires that a configuration file be created before
it can function. The sample configuration file denyhosts.cfg-dist
contains most of the possible settings and should be copied and
then edited as such:

# cp denyhosts.cfg-dist denyhosts.cfg

# denyhosts.cfg

(where is your preferred text editor such as emacs, vi, etc)

The sample configuration file contains informational comments that
should help you quickly configure DenyHosts. After you have
edited your configuration file, save it.

Next, if you intend to run DenyHosts in daemon mode (recommended)
copy the sample daemon-control.dist script as such:

# cp daemon-control-dist daemon-control

Edit the daemon-control file. You should only need to edit this section
near the top:

###############################################
#### Edit these to suit your configuration ####
###############################################

DENYHOSTS_BIN = "/usr/bin/denyhosts.py"
DENYHOSTS_LOCK = "/var/lock/subsys/denyhosts"
DENYHOSTS_CFG = "/usr/share/denyhosts/denyhosts.cfg"

These defaults should be reasonable for many systems. You
should customize these settings to match your particular
system.

Once you have edited the configuration and daemon control files
make sure that the daemon control script it executable (by root).

# chown root daemon-control

# chmod 700 daemon-control

STARTING DENYHOSTS MANUALLY
===========================

Assuming you have configured DenyHosts to run as a daemon, you
can use the daemon-control script to control it:

# daemon-control start

You should refer to the daemon log (typically /var/log/denyhosts)
to ensure that DenyHosts is running successfully. If you
notice any problems you may wish to consult the FAQ at
http://www.denyhosts.net/faq.html

If you wish to run DenyHosts from cron rather than as a
daemon, please refer to the FAQ.

STARTING DENYHOSTS AUTOMATICALLY
================================

METHOD 1 (preferred)
====================

Create a symbolic link from /etc/init.d such as:

# cd /etc/init.d

# ln -s /usr/share/denyhosts/daemon-control denyhosts

If you have chkconfig installed you can then use it to
ensure that DenyHosts runs at boot time:

# chkconfig --add denyhosts

If you do not have chkconfig (or similar) installed you can either manually
create the symlinks in /etc/rc2.d, /etc/rc3.d, /etc/rc5.d but that is beyond
the scope of this document.

METHOD 2
========

Add an entry into the /etc/rc.local file:

/usr/share/denyhosts/daemon-control start

Installing PHP on Ubuntu

2009-05-04T05:44:00.000-07:00

To install PHP on Ubuntu 8.10, issue the following command:

#apt-get install php5
#apt-get install libapache2-mod-php5

Disallow Root Login on SSHD

2009-05-01T07:06:00.000-07:00

To disallow root login access on ssh, open the file "/etc/ssh/sshd_config" and edit or add the line:

PermitRootLogin no

Then restart your sshd server:

#/etc/rc.d/init.d/sshd restart

Installing Dovecot on CentOS

2009-05-01T05:46:00.000-07:00

To install the Dovecot on your CentOS 5.2 server, issue the command:

#yum install dovecot

If you are installing the RPM package that comes with the CD, the command to install dovecot is:

#rpm -Uvh dovecot-1.0.7-2.el5.i386.rpm

What is port 111 on my CentOS box?

2009-05-01T05:37:00.000-07:00

Port 111 on my CentOS 5.2 box is the "portmap" service. You can turn this off by issuing the following command:

#/etc/rc.d/init.d/portmap stop

By default, this is turned on my machine. So upon reboot of your machine, expect that is again turned on. If you want to set the default execution to off, issue the command:

#chkconfig --levels 2345 portmap off

Home Directory of Solaris

2009-04-26T02:23:00.000-07:00

The default home directory of Solaris 2008.11 is "/export/home". This location is different from all distributions of Linux which places the user's home directories under "/home".

Installing Flash Player on Firefox under Solaris 2008.11

2009-04-26T02:16:00.000-07:00

The following are the steps on how to install the flash player in Firefox under Solaris 2008.11:

1. Download the flash player package at the www.adobe.com website (flash_player_10_solaris_x86.tar.bz2)

2. Unpack the package by clicking on the file and clicking the "extract" button

3. On the extracted directory, copy the file (libflashplayer.so) and place it under the directory "/usr/lib/firefox/plugins"

4. Restart Firefox

Review of Solaris 2008.11

2009-04-26T01:35:00.000-07:00

If you are like me who enjoys testing various operating systems, then you must have heard about Solaris. Solaris is an industrial-grade server operating system published by Sun Microsystems. I've always wanted to test drive Solaris but I don't have the resources to do so, up still recently when Sun placed Solaris under open source. Now I can test drive the system.

I tried downloading the latest Solaris version that comes under the name OpenSolaris 2008.11. Here are my notes:

Desktop

Solaris now sports a pretty GNOME desktop interface. So if you are an old Linux hand like me, you will feel at home with the graphical user interface.

RAM

Solaris 2008.11 requires a huge memory to effectively install it. On my machine, it required 512MB of RAM. Anything lower, the system will not install.

Home Directory

To my surprise, the user's home directory is not located in "/home" unlike in all distributions of Linux. It is located in "/export/home".

User Name

Solaris still does not support long usernames. So you will have to make do with an 8-letter username.

Internet Browser

The default Internet browser is Mozilla Firefox. However, you cannot view "youtube" since flash has to be manually installed. Fortunately, there is a flash player available for Solaris which you can download from www.adobe.com.

To install the flash player, download and unpack the flash player package (flash_player_10_solaris_x86.tar.bz2). The package only contains one file (libflashplayer.so) and does not contain any instructions on how to install it. So I tried experimenting with it given my knowledge of Firefox. Here is what I did:

a) I copied the file (libflashplayer.so) to the Firefox plugin directory at "/usr/lib/firefox/plugins"
b) Then, I restarted Firefox.

I went immediately to youtube to test if the flash player will work. To my delight, it did!

Office Suite

OpenOffice is not part of the installer CD. But my guess is, it can easily be installed since it is published by Sun Microsystems.

Network Card

Solaris 2008.11 still got limited network card support unlike Linux. I tried installing it on three other desktops, it did not work. There was no driver support for the network card.

Sound

On all three desktops and 1 laptop I installed Solaris 2008.11 on, none of the built-in sound card was supported. I did not investigate any further as all distributions of Linux do not have problems with the sound card on all of those machines. My guess is, Solaris 2008.11 still needs some polishing in terms of its driver support.

Installing VirtualBox

2009-04-25T06:38:00.000-07:00

VirtualBox is a software package that allows you to install Windows in a virtual environment. Under Ubuntu 8.10 and 9.04, VirtualBox can be installed by issuing the following command:

#apt-get install virtualbox

Adjusting Image Sizes in GIMP

2009-04-17T03:36:00.000-07:00

To adjust image sizes in GIMP, click on "Image"->"Scale".

Installing Squid on Ubuntu

2009-04-17T03:27:00.000-07:00

Squid is an industrial grade web proxy server cache. To install squid on Ubuntu 8.10, issue the following command:

#apt-get install squid

Installing Squirrelmail on Ubuntu

2009-04-16T08:56:00.000-07:00

To install the Squirrelmail web interface software on Ubuntu 8.10, issue the command:

#apt-get install squirrelmail

Installing BIND on Ubuntu

2009-04-16T08:54:00.000-07:00

To install BIND on Ubuntu 8.10, issue the command:

#apt-get install bind9

Installing ISC's DHCP Server on Ubuntu

2009-04-16T08:51:00.001-07:00

To install ISC's DHCP server on Ubuntu 8.10, issue the following command:

#apt-get install dhcp

The configuration file of the ISC's DHCP server (dhcpd.conf) is located in the director "/etc/dhcp3".

The server can be started by issuing the command:

#/etc/dhcp3-server start

GIMP Commands for Slicing Images

2009-04-16T08:42:00.000-07:00

Why do you want to slice images? Well, for most web designers, slicing images into smaller image files tend to make the images load faster when using a browser. GIMP allows you to easily slice images and create the corresponding HTML fragment file which you can copy and paste to your web page. Here is how:

1. Go to the menu "Image"->"Guides"->"New Guide"
2. Then select the preferred guide. Usually you either choose horizontal or vertical. Choosing horizontal will give you a horizontal guide rule which you can transfer to the part of the image you want sliced.
3. To slice, click on the menu "Filter"->"Web"->"Slice"

Installing Dovecot IMAP4 and POP3 Mail Delivery Agent on Ubuntu

2009-04-16T08:38:00.000-07:00

Dovecot is a secured IMAP4 and POP3 mail delivery agent (MDA). To install, issue the following command:

#apt-get install dovecot-imapd
#apt-get install dovecot-pop3d

The configuration file of Dovecot (dovecot.conf) can be found in the directory "/etc/dovecot".

The package usually works in tandem with the Postfix SMTP mail transfer agent (MTA). I've tested the above commands under Ubuntu 8.10.

Installing the Postfix SMTP Mail Server on Ubuntu

2009-04-16T08:36:00.000-07:00

To install the Postfix SMTP mail server on Ubuntu 8.10, issue the command:

#apt-get install postfix

Installing MySQL on Ubuntu

2009-04-16T08:31:00.000-07:00

As always, various distributions of Linux have different ways of naming their software packages. In the case of Ubuntu 8.10 Linux, the software packages for MySQL database system are: "mysql-client" and "mysql-server". To install MySQL on Ubuntu, issue the following commands:

#apt-get install mysql-client
#apt-get install mysql-server

Installing Apache on Ubuntu

2009-04-15T08:10:00.000-07:00

Ubuntu is one of the Linux distributions that grew out of the Debian Linux distribution. Unlike the RedHat-based distributions (RedHat, Fedora, CentOS and Mandrake), installation under Ubuntu does not use the "yum" command. Instead it uses the "apt-get" command. Variation also exists between the package names under Ubuntu and those of the RedHat-based distributions.

Installing the Apache web server under Ubuntu uses the following command:

#apt-get install apache2

As you may have noticed, the package name for the Apache web server is "apache2" instead of "httpd" under RedHat-based distributions.

You can also install the accompanying PHP scripting engine by issuing the following commands:

#apt-get install php5
#apt-get install libapache2-mod-php5

The home directory of the Apache web server is located in "/var/www" directory instead of "/var/www/html" directory under RedHat-based distributions.

I've tested the above procedure under Ubuntu 8.10.

What is Port 898 on my CentOS box?

2009-03-05T18:58:00.000-08:00

What is port 898 on my Linux CentOS box? Using the #nmap program, I was able to verify that on my system port 898 is open and the service name is "sun-manageconsole". Since I do not know what sun-manageconsole is, I issued the #lsof command to verify what open file is associated with it:

#lsof | grep 898

This gave me the information that its "rpc.statd". I did a quick google search on what rpc.statd is. Accordingly, this is run by the service "nfslock". Since on the server, you will not be using nfs, I quickly deactivated the service and remove it in my startup:

# /etc/rc.d/init.d/nfslock stop
# chkconfig --levels 2345 nfslock off

The next #nmap command no longer shows port 898, which gave a sigh of relief knowing no server process that I don't know about is running.

By the way, researching a bit further, I found out that "nfslock" may also run on other ports besides 898.

What process is running on the port?

2009-03-05T18:53:00.000-08:00

Have you wondered what process is running on the port of your Linux box? The command to know the process that is running on the port is:

#lsof

This command comes handy with the #nmap program that identifies what ports are open. The command however tries to list all open files and therefore expect a long list to run through your screen. If you just want to investigate a particular port say port 898, use #lsof with grep:

#lsof | grep 898

This will list the open files with the particular port 898.

Knowing What Ports Are Open on Linux?

2009-03-05T18:48:00.000-08:00

On Linux, it is easy to know what ports are open. You just need to use the program "nmap". If you don't have it on your system, download and install it using the command:

#apt-get install nmap

on your Ubuntu or using the yum for Fedora/RedHat/CentOS as follows:

#yum install nmap

Once installed, issue the command:

#nmap localhost

to know which ports are open in your computer.

PHP Support in the Apache Webserver

2009-02-17T03:57:00.000-08:00

The following are my notes on PHP support in the Apache Webserver. The Linux box I am using runs on CentOS 5.0 operating system. The following steps assumes that the Linux box is connected to the Internet:


# yum install httpd
# yum install php
# yum install php-mysql
# yum install php-pgsql
# yum install php-mbstring
# yum install php-xmlrpc
# yum install php-gd

Among others, the above commands installs Apache and PHP with support for the MySQL and PostgreSQL databases.

Virtual Hosting in Apache

2009-02-17T03:11:00.000-08:00

Virtual hosting is the ability of webserver to host more than one domain. The Apache webserver supports virtual hosting. Here are the steps on how to do it.

Considerations:
The web pages will be stored in the home folder of the user such as "/home/bse/www/html". Normally, Apache locates the web pages under the directory "/var/www/html".

I am using CentOS 5.0 (http://www.centos.org) as my operating system of choice.

This setup assumes that you are connected to the Internet.

Here are the steps...

Step 1:
Download the Apache software as follows:


#yum install httpd

Step 2:
Create the virtual file "virtual.conf" under the directory "/etc/httpd/conf.d". The "virtual.conf" file should read as follows:


ServerName idep01.bse.deped.gov.ph

< Directory /home >
    Order Deny,Allow
    Allow from all
    DirectoryIndex index.html index.htm index.php index.phtml
< /Directory >

NameVirtualHost *:80

< VirtualHost *:80 >
    ServerName www.bse.deped.gov.ph
    DocumentRoot /home/bse/www/html
    ErrorLog /home/bse/www/logs/error_log
    TransferLog /home/bse/www/logs/access_log
< /VirtualHost >




Step 3:
Create the user and folders for the web pages as follows:


# adduser bse
# mkdir /home/bse/www
# mkdir /home/bse/www/html
# mkdir /home/bse/www/logs
# touch /home/bse/www/logs/error_log
# touch /home/bse/www/logs/access_log

Step 4:
Change the ownership and permissions of the "bse" user and its home folders. I assume that Apache is owned by the user "apache" and group "apache". Here are the commands:


# chown -R bse.apache /home/bse
# chmod -R 755 /home/bse

Step 5:
Copy a test page with the filename "index.html" to the directory "/home/bse/www/html".

Step 6:
Start the Apache web server as follows:


# /etc/rc.d/init.d/httpd start

Verify if you got it right by pointing your browser to the web address of the Apache webserver.

Setting up a Master DNS Server

2009-02-17T00:29:00.000-08:00

These are my notes on setting up a master DNS server. DNS is short for Domain Name System. The DNS is responsible for translating computer addresses in the form of numbers into human understandable convention like "www.google.com".

First, my system. The operating system that I am installing to is a CentOS 5.0 Linux box. If you are not familiar with the CentOS Linux distribution, CentOS is generally a "Red Hat Enterprise Product" distribution intended for production deployments without the branding and support of Red Hat. It is in many ways the same as the Red Hat Enterprise Linux product and is related to the Fedora distribution.

Setting up the master DNS server requires the following steps:

Step 1:
Download and install the BIND software. BIND is short for Berkeley Internet Name Domain. I am assuming that you are connected to the Internet. The command to do that is:


# yum install bind
# yum install bind-utils

Step 2:
Create the configuration file "named.conf" in the directory "/etc". The file "named.conf" should read as follows:


zone "0.0.127.in-addr.arpa" {
   type master;
   file "mylocalhost";
};

zone "bse.deped.gov.ph" {
   type master;
   notify no;
   file "bse.deped.gov.ph";
};

zone "126.126.222.in-addr.arpa" {
   type master;
   notify no;
   file "222.126.126";
};

Step 3:
Create the file "mylocalhost" in the directory "/var/named". The "mylocalhost" file should read as follows:


$TTL 3D
@     IN     SOA     ns.bse.deped.gov.ph.     hostmaster.bse.deped.gov.ph. (
    1     ; serial
    8H    ; Refresh
    2H    ; Retry
    4W    ; Expire
    1D)   ; Minimum TTL

    NS     ns.bse.deped.gov.ph.

1     PTR     localhost.

Step 4:
Create the zone file for the domain like "bse.deped.gov.ph" in the directory "/var/named". The file "bse.deped.gov.ph" should read as follows:


$TTL 3D
@     IN     SOA     ns.bse.deped.gov.ph.     hostmaster.bse.deped.gov.ph. (
    19980214     ; serial
    8H     ; refresh
    2H     ; retry
    4W     ; expire
    1D)    ; minimum TTL

    NS     ns
    MX     10     mail01.bse.deped.gov.ph.
           20     mail02.bse deped.gov.ph.

localhost     A     127.0.0.1
www           A     222.126.126.211

ns            A     222.126.126.211
mail01        A     222.126.126.211
mail02        A     222.126.126.212

Step 5:
Create the reverse domain file such as "222.126.126" in the directory "/var/named". The file "222.126.126" should read as follows:


$TTL 3D
@     IN     SOA     ns.bse.deped.gov.ph.     hostmaster.bse.deped.gov.ph.   (
    19980214     ; serial
    8H           ; Refresh
    2H           ; Retry
    4W           ; Expire
    1D )          ; Minimum TTL

    NS     ns.bse.deped.gov.ph.

211     PTR     www.bse.deped.gov.ph.

Step 6:
Start the server as follows:


# /etc/rc.d/init.d/named start
Starting named:                                            [  OK  ]

If there are no errors proceed to the next step. If there are errors, double check on the contents of the setup files.

Step 7:
Check the name resolution functionality of your server by using the "nslookup" utility that comes with the "bind-utils" package as follows:


# nslookup www.bse.deped.gov.ph
Server:  127.0.0.1
Address: 127.0.0.1#53

Name: www.bse.deped.gov.ph
Address: 222.126.126.211

# nslookup 222.126.126.211
Server:  127.0.0.1
Address: 127.0.0.1#53

211.126.126.222.in-addr.arpa name = www.bse.deped.gov.ph.

Raw Printing in Linux

2008-12-19T07:10:00.000-08:00

Raw printing in Linux is achieved by issuing the command and piping the result to /dev/lp0. For example:

# ls -l > /dev/lp0

Raw printing is useful if you want to take advantage of fast printing using the default fonts of the printer. More often, this is useful if you will be printing under a dot matrix printer.

Furthermore, you can also issue printer codes to the printer to make condensed printing as follows:

# echo -ne '\033\017' >> /dev/lp0

The printer code "\033\017" is an octal equivalent for condensed printing under an Epson-like dot matrix printers. Commonly, the following codes may also be used:

\033\115 for elite and \033\120 for pica

If you are using a different dot matrix printer, the printer codes are found in your printer manual.

Solution to PostgreSQL Serial Limitations

2008-12-19T05:55:00.000-08:00

In PostgreSQL, an automatic incrementing column is called "serial". This is often used as a primary key of a table. The default serial column is of type INT4 which has a maximum value of 2,147,483,647. To increase this maximum number, create an INT8 data type for your serial column, as follows:


>CREATE SEQUENCE person_id_seq;
>CREATE TABLE person( id INT8 NOT NULL DEFAULT nextval('person_id_seq'), name TEXT);
>CREATE UNIQUE INDEX person_id_key on person(id);

This will increase the capacity of the column to 9,223,372,036,854,775,807. I don't know if there is an INT16 column type. If there is, theoretically we can increase further the capacity of the column by a factor of 2 since PostgreSQL does not support unsigned integers as far as I know.

Solution to MySQL auto_increment Limitations

2008-12-19T05:40:00.000-08:00

By default, MySQL's auto_increment column has a maximum number of 2,147,483,647. In practice, this number may even be less since the next NULL insert to the table will use the next value of the highest insert number. Consequently, once you have reached the maximum number, the next null insert will cause an error because of the occurrence of a duplicate key.

The solution to MySQL's auto_increment limitations is to create a primary key as an UNSIGNED BIGINT(20) type. As an example for the table "mytest", issue the following MySQL command:


>CREATE TABLE mytest(p_id BIGINT(20) UNSIGNED PRIMARY KEY AUTO_INCREMENT, name CHAR(10) );

The UNSIGNED BIGINT(20) type has a maximum number of 18,446,744,073,709,551,616. A SIGNED BIGINT(20) type has a maximum number of 9,223,372,036,854,775,807. Since you will be using this as a non-duplicating primary key in your table, most likely you will be using the UNSIGNED BIGINT(20) type since there is no need for storing negative values.

Firewall Script

2008-12-19T04:54:00.001-08:00

The following is a sample firewall script on Linux. It also acts as a network address translation (NAT) script that masquerades the IP addresses of the local area network. The script assumes that the local area network is in the 192.168.0.0 network class. Here it is:


# Load Modules
modprobe ip_conntrack
modprobe ip_conntrack_ftp

echo 1 > /proc/sys/net/ipv4/ip_forward

# Flush rules
iptables -F 
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X

# Default Deny Policy
iptables -P INPUT DENY
iptables -P OUTPUT DENY
iptables -P FORWARD DENY

# Perform NAT
iptables -t nat -A POSTROUTING -s 192.168.0.0/255.255.255.0 -d 0.0.0.0/0.0.0.0 -j MASQUERADE

Removing Comment Lines and Spaces in a File

2008-12-18T18:05:00.001-08:00

How to remove comment lines and spaces on a configuration file in Linux?

To remove comment lines under Linux, issue the following command:


# sed -e '/^#/d' -e '/^$/d' < squid.conf > newsquid.conf

Then, go can backup the original squid.conf file by copying it to say squidconf.bak:


# cp squid.conf squidconf.bak

And finally copying the new squid file to replace the original file as:


# cp newsquid.conf squid.conf

DHCP 3.x Server Configuration

2008-12-18T17:56:00.000-08:00

The following is the DHCP 3.x configuration file "dhcpd.conf" on a Linux server:

-- Start of Configuration File --


ddns-update-style interim;
ignore client-updates;

subnet 192.168.0.0 netmask 255.255.255.0 {
range 192.168.0.100 192.168.0.200;
option routers 192.168.0.254;
option subnet-mask 255.255.255.0;
option domain-name "portal.ph";
option domain-name-servers 192.168.0.1;
option netbios-name-servers 192.168.0.1;
default-lease-time 21600;
max-lease-time 43200;
}

-- End of Configuration File --

Recovering Lost MySQL Password

2008-12-18T06:10:00.000-08:00

The following are the steps on how to recover lost passwords in MySQL.

Steps:

1. Kill the MySQL daemon.

(the command on a RedHat-based system)
# /etc/rc.d/init.d/mysqld stop

2. Run the command:

# safe_mysqld --skip-grant-tables&
(on Fedora Core 5, the command is "mysqld_safe" instead of "safe_mysqld")

3. Go to the CLI.

#mysql
> use mysql
> update user set password=password('test123') where user='root' and host='localhost';
>\quit

4. Stop the MySQL

#mysqladmin -u root -p shutdown

5. Rerun MySQL

# /etc/rc.d/init.d/mysqld start

You can now access your database using the new password 'test123' as follows:

#mysql -u root -ptest123

HTTP Proxy Script in Python

2008-12-16T02:23:00.001-08:00

The following is an HTTP proxy script written by Suzuki Hisao using the Python programming language. I lifted this post from the original posting at http://mail.python.org/pipermail/python-list/2003-June/210343.html since I may have need for this script in the future. I have tested this script and it works great. Its even better than the one I wrote using the Ruby programming language. Thanks Mr. Suzuki Hisao for sharing this with us.


----------------------------------------------------------------
#!/bin/sh -
"exec" "python" "-O" "$0" "$@"

__doc__ = """Tiny HTTP Proxy.

This module implements GET, HEAD, POST, PUT and DELETE methods
on BaseHTTPServer, and behaves as an HTTP proxy.  The CONNECT
method is also implemented experimentally, but has not been
tested yet.

Any help will be greatly appreciated.  SUZUKI Hisao
"""

__version__ = "0.2.1"

import BaseHTTPServer, select, socket, SocketServer, urlparse

class ProxyHandler (BaseHTTPServer.BaseHTTPRequestHandler):
   __base = BaseHTTPServer.BaseHTTPRequestHandler
   __base_handle = __base.handle

   server_version = "TinyHTTPProxy/" + __version__
   rbufsize = 0                        # self.rfile Be unbuffered

   def handle(self):
       (ip, port) =  self.client_address
       if hasattr(self, 'allowed_clients') and ip not in self.allowed_clients:
           self.raw_requestline = self.rfile.readline()
           if self.parse_request(): self.send_error(403)
       else:
           self.__base_handle()

   def _connect_to(self, netloc, soc):
       i = netloc.find(':')
       if i >= 0:
           host_port = netloc[:i], int(netloc[i+1:])
       else:
           host_port = netloc, 80
       print "\t" "connect to %s:%d" % host_port
       try: soc.connect(host_port)
       except socket.error, arg:
           try: msg = arg[1]
           except: msg = arg
           self.send_error(404, msg)
           return 0
       return 1

   def do_CONNECT(self):
       soc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
       try:
           if self._connect_to(self.path, soc):
               self.log_request(200)
               self.wfile.write(self.protocol_version +
                                " 200 Connection established\r\n")
               self.wfile.write("Proxy-agent: %s\r\n" % self.version_string())
               self.wfile.write("\r\n")
               self._read_write(soc, 300)
       finally:
           print "\t" "bye"
           soc.close()
           self.connection.close()

   def do_GET(self):
       (scm, netloc, path, params, query, fragment) = urlparse.urlparse(
           self.path, 'http')
       if scm != 'http' or fragment or not netloc:
           self.send_error(400, "bad url %s" % self.path)
           return
       soc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
       try:
           if self._connect_to(netloc, soc):
               self.log_request()
               soc.send("%s %s %s\r\n" % (
                   self.command,
                   urlparse.urlunparse(('', '', path, params, query, '')),
                   self.request_version))
               self.headers['Connection'] = 'close'
               del self.headers['Proxy-Connection']
               for key_val in self.headers.items():
                   soc.send("%s: %s\r\n" % key_val)
               soc.send("\r\n")
               self._read_write(soc)
       finally:
           print "\t" "bye"
           soc.close()
           self.connection.close()

   def _read_write(self, soc, max_idling=20):
       iw = [self.connection, soc]
       ow = []
       count = 0
       while 1:
           count += 1
           (ins, _, exs) = select.select(iw, ow, iw, 3)
           if exs: break
           if ins:
               for i in ins:
                   if i is soc:
                       out = self.connection
                   else:
                       out = soc
                   data = i.recv(8192)
                   if data:
                       out.send(data)
                       count = 0
           else:
               print "\t" "idle", count
           if count == max_idling: break

   do_HEAD = do_GET
   do_POST = do_GET
   do_PUT  = do_GET
   do_DELETE=do_GET

class ThreadingHTTPServer (SocketServer.ThreadingMixIn,
                          BaseHTTPServer.HTTPServer): pass

if __name__ == '__main__':
   from sys import argv
   if argv[1:] and argv[1] in ('-h', '--help'):
       print argv[0], "[port [allowed_client_name ...]]"
   else:
       if argv[2:]:
           allowed = []
           for name in argv[2:]:
               client = socket.gethostbyname(name)
               allowed.append(client)
               print "Accept: %s (%s)" % (client, name)
           ProxyHandler.allowed_clients = allowed
           del argv[2:]
       else:
           print "Any clients will be served..."
       BaseHTTPServer.test(ProxyHandler, ThreadingHTTPServer)
----------------------------------------------------------------

Comparing Costs with Different Time Periods

2008-10-16T19:34:00.000-07:00

How do you compare costs with different time periods?

To answer the above question, people who have no background in Economics or Finance will just ignore the difference in the time periods of costs. So the analysis becomes simple, it is a matter of comparing the cost items. The resulting comparison while theoretically is wrong is practical especially under three (3) conditions:

1. The time period involved is too short, say 2 years;
2. The amount is too small, say a few hundred pesos; and
3. The interest rate is too low, say less than 1%.

Whoa! interest rate? What has interest rate got to do with comparing costs? Well, interest rate is the cost differences between the two periods. Say if you got P1.00 now and you place it in a bank for 2 years and your deposit registered P1.20, the P1.00 now can be said to be equal to P1.20 after two years. The differences between now and the future value is the interest rate earned or foregone. Economists refer to this as the "opportunity cost of capital".

In most investments situations, you will be faced with decisions involving costs at difference time periods. So it is best that you know how much is the interest rate. In the above example, the interest rate is 10% per year.

So when comparing costs at different time periods, know the interest rate. Use it as a gauge in deciding which costs are higher or lower. In investment decision-making, if the yield from an investment is say 20% and the interest rate is 10%, then you gain by 10% if you decide to invest. Assuming all other things to be equal.

If however the investment yield is only 5%, and the interest rate is 10%, then the investment is not attractive since you will actually be losing 5% have you decided to put your money in the bank that yields 10%.

In short, faced with an investment decision problem, don't just compare costs without regard to its time period. You may lose money in the process. But if it does not involve much money, then perhaps, it is just practical to compare costs without regard to its time period.

Page Numbering in OpenOffice

2008-10-02T06:55:00.000-07:00

Of late, I have to write a long report. So being an open source enthusiast, I decided to use OpenOffice instead of Microsoft Office. Guess what? Page numbering under OpenOffice is a bit cumbersome. In fact, I have to search the web for answer and it would seem that I am not the only one experiencing the problem. So after some playing around with OpenOffice, I finally was able to do the things I need for a long report. Here it is...

(1) Page Numbering

The procedure is to go "Insert->Footer->Default", then "Insert->Fields->Page Number". If you want your page number to appear in the header, use "Insert->Header->Default", then "Insert->Fields->Page Number".

Quite cumbersome, but still if you are an old hand in using computers, you may eventually figure that out. Here is the more difficult part. How do you insert a page number that does not start with page 1? It took me hours to figure it out. But since, I cannot find a solution also online, I had vowed to post the procedure online. Here it is...

(2) Starting a page number not from the default page 1, say page 20 ...

The procedure is to locate your cursor on the first paragraph where you want the page to start. Then, go "Format->Paragraph" then select the "Text Flow" tab. Under the "Breaks" line, check the "Insert", and check the "With Page Style", then indicate your desired page number under "Page Number".

Very cumbersome. I think, the creators of OpenOffice can make this more intuitive since regularly writers will need this feature. Sigh!

About Me

2008-09-08T07:35:00.000-07:00

Hello! My name is Clement Rasul. I am an information and communication technology (ICT) and project management (PM) specialist. My professional interests are: (i) Statistics, (ii) Economics, (iii) Information and Communication Technology, (iv) Project Management, and (v) Management Consultancy.