dos2unix — DOS/MAC to UNIX text file format converter.

Summary:

Each OS will indicate the line end differently using Line Feed (LF,10)
or Carriage Return (CR,13). So when tranfering a file from DOS to
Unix, you have to convert the Line end from DOS format to Unix format.

dos2unix will convert the DOS/MAC Text file to Unix format. Unix or
Linux uses LF as line end, Windows/DOS uses CR/LF and MacOS uses CR.

Examples:

$ dos2unix dos.txt — Convert and replace dos.txt.

$ dos2unix -n dos.txt gnu.txt — Convert dos.txt and
write into gnu.txt

$ dos2unix -k dos.txt — Convert and replace a.txt while
keeping original date stamp.

Read: man dos2unix

How to view the process activity in ubuntu 9.04?

Top is a command that provides a dynamic real-time view of a running system By default, it

By default – Displays CPU-intensive tasks running on the server

Some Hot keys provided in TOP command

t  – Displays summary information off and on.
m – Displays memory information off and on.
A – Sorts the display by top consumers of various system resources.
f -  Enters an interactive configuration screen for top.
o – Enables you to interactively select the ordering within top.
r – Issues renice command. k Issues kill command.
z – Turn on or off color/mono

How to find Virtual Memory PAGESIZE in Ubuntu 9.04 ?

A page is a fixed length block of main memory, that is contiguous in both physical memory addressing and virtual memory addressing.

Kernel swap and allocates memory using pages

To Know the PAGESIZE

$ getconf PAGESIZE

result :
verman@verman-desktop:~/$ getconf PAGE_SIZE
4096

How to check Linux kernel in your PC?

uname command with the -a option prints all system information, including machine name,kernel name & version, and a few other details.

For Example :

verman@verman-desktop:~$ uname -a
Linux verman-desktop 2.6.22-14-generic #1 SMP Sun Oct 14 23:05:12 GMT 2007 i686 GNU/Linux

Check here for more info

How to check Linux release in your PC?

lsb_release command with the -a option prints
version information for the Linux release you’re running

For Example :

verman@verman-desktop:~$ lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 7.10
Release: 7.10
Codename: gutsy

Command : $bg

bg — Place a job in BackGround

Summary:

Normally user can run a job in background, by adding & at end of the
command (ex: sleep 10 &).

bg is a shell command. It is used to move a job from foreground to the
background, as if it had been started with `&’. If JOB is not present,
the shell’s notion of the current job is used.

Examples:

$ sleep 100 — Start a dummy job in foreground.
Press Ctrl+z to stop the current job.

$ bg — Move the last stopped job to background.

$ sleep 150 — Dummy job 1
Press Ctrl+z to stop the current job.

$ sleep 140 — Dummy job 2
Press Ctrl+z to stop the current job.

$ sleep 130 — Dummy job 3
Press Ctrl+z to stop the current job.

$ jobs — List all active jobs.

$ bg 2 — Move the 2nd active job to background.

Read: help bg, jobs

Command : $last

last — Show listing of last logged in users.

Summary:

Last searches back through the file, by default, /var/log/wtmp (or -f
file) and displays a list of all users logged in and out, since that
file was created. It shows User Name, Terminal No, Host IP, Login
Date & Time, Logout Time and Total Time.

Examples:

$ last — List all entries.

$ last tty6 — List, who are all logged thru tty6.

$ last pts/6 — List, who are all logged thru pts/6.

$ last bharathi — List all entries of bharathi (user).

$ last -6 — List only last 6 entries.

$ last -R — Don’t show the Host Name field in output.

$ last -a — Show Host Name field in last column.

$ last -i — Show IP Number for Remote host.

$ last -t 20050818120000 — List all entries upto Aug 18 12:00:00 2005.

Read: man last

apt-cache — Debian APT package handling utility

apt-cache — Debian APT (Advanced Package Tool) package handling utility.

Summary:

apt-cache performs a variety of operations on APT’s package cache.
apt-cache does not manipulate the state of the system, but does
provide operations to search and generate interesting output from
the package meta-data (/var/lib/apt/lists).

Examples:

$ apt-cache search xfree86 — Show package info and descriptions for the search-string (xfree86).

$ apt-cache policy gcc — Show version and priorities of the available Packages.

$ apt-cache show postgresql — Show detailed description of postgresql package.

$ apt-cache showpkg mozilla — Show all kind of dependencies for the Mozilla package.

$ apt-cache depends mozilla — List the packages needed by Mozilla.

$ apt-cache rdepends kde — List all packages that needs KDE.

Read: man apt-cache

Command : $chvt

chvt — CHange foreground Virtual Terminal.

Summary:

In GNU/LINUX OS, be default, 6 virtual text mode console terminals
will be running. User can switch between this terminals using Left
Side Ctrl + Alt + FunKey(1 – 6).

chvt command is also used to switch between this terminals. It can
be used in shell scripts.

Examples:

$ chvt 1 — Switch from current terminal to /dev/tty1.

$ chvt 2 — Switch from current terminal to /dev/tty2.

Read: man chvt

TIP: Screen Dump in Text console.

# sudo cat /dev/vcs2 > scrdump.txt — Take the screen dump of
/dev/tty2 in scrdump.txt file.

apt-get — Debian Package Manager

Summary:

apt-get is a powerful package manager used in the Debian Distro. It is
in-build capability to resolve the conflicts and dependencies.

Examples:

# apt-get update — Update the Pkg listings from package repositories.

# apt-get upgrade — Install newest versions of all packages currently installed.

# apt-get dist-upgrade — Same as above. But with advanced conflict resolution capability.

# apt-get install newpkg — Install the ‘newpkg’ from repositories with all dependencies.

# apt-get remove pkgName — Remove the package with all needed packages.

Read: man apt-get