Quick way to figure out, which ports a particular program is using in linux

[bash] netstat -plan | grep -i PROGRAM_NAME [/bash]

Example : Check which ports SSH is listening on

[bash]

samurai@samurai:~$ sudo /bin/netstat -plan | grep sshd
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      5257/sshd
tcp        0     52 123.123.123.123:22      124.124.124.124:32846     ESTABLISHED 3551/sshd: samurai
tcp6       0      0 :::22                   :::*                    LISTEN      5257/sshd
unix  3      [ ]         STREAM     CONNECTED     5893     3551/sshd: samurai
unix  2      [ ]         DGRAM                    5849     3551/sshd: samurai

[/bash]

Most Redhat/Fedora users are used to chkconfig and service for controlling the services/programs that startup at boot time. Here is how you do it in Ubuntu

• Check status of a particular service

[bash] sudo SERVICE_NAME status [/bash]

Example : Check the status of Apache Web Service

[bash]samurai@samurai:~$ sudo service apache2 status
Apache is running (pid 3496).[/bash]

• Add a service to start on bootup

[bash] update-rc.d SERVICE_NAME add [/bash]

Example : Configure squid to start on bootup

[bash] update-rc.d squid add [/bash]

• Stop a service from starting on bootup

[bash] update-rc.d SERVICE_NAME remove [/bash]

Example : Configure squid to NOT start on bootup

[bash] update-rc.d squid remove [/bash]

NOTE : You need to have a startup script in /etc/init.d for the service to ensure update-rc.d works fine.

For my notes.. if you ever want to check the IO capability of a disk (local or network) on a linux machine, use the following command

[bash] dd if=/dev/zero of=test.file bs=4M count=1000 [/bash]

The above command make a copy of the output from /dev/zero to a file called test.file (you can locate the file on the disk you want to measure) with a block size of 4M for a total file size of 4000Mb.