Linux Basic Commands and Memory relarated commands Very usefull

Linux Basic Commands-Memory related commands

login to the unix/solaris server ip or host name

Ex-   ip 10.1.21.1   host  usex10alg

username: wesrg

passwd         : *******

You will log in to the server. It will take you to default home_directory.

- pwd

it shows/prints the present working directory

-ls -l

gives listing of the files in present directory

-cd ..

takes you to previous directory

mkdir <directory>

will create directory

 -mkdir -p /home/jb/j1/j2/j3

will create all the non-existing directories at a stretch

-vi <file_name>

opens file for reading/editing

-cat <file_name>

display contents of file

-more <file_name>

displays page by page contents of file

-tail <file_name>

shows last 10 lines of file

use tail -f for continous update of file_name

-head <file_name>

shows first 10 lines of file_name

 -touch <file_name>

creates a zero/dummy file

-ln file1 file2

creates link of file1 to file2

-file <file_name>

shows what type of file it is like

-$ file *

acrawley.html:  ascii text

admin:          directory

afiedt.buf:     ascii text

autosys_env_IBKNYR1:    commands text

-cd /home/<directory_name>

takes you to /home/<directory_name> directory

likewise you can give and directory

Note: remember to give from the beginning like '/' is very important. Its called the root directory. In Unix/solaris/<any_falvor_of_unix> path is 

-clear

clears the screen

 -cd /usr/bin

Similarly /usr/sbin has administrative related commands

-/usr/lib has libraries

and

-/etc consists of system administrative and tuning files

-who

will display which users are logged into system.

-$w

will  display more info abt the users logged in

once you login to the system your home directory will be set. in between if you navigate/go to other directories and after that if you give "cd " it will take you back to your home direcory.

 ps -ef

shows process status of various active processes.(use more/other options to get more info)

 rm <file_name>

will delete file specified

rm *

will delete all the files in the present directory (BE CAREFUL WHILE GIVING THIS COMMAND)

-grep <pattern> file_name

checks pattern/word in file name specified

-chmod 777 <file_name>

changes file_name/directory permissions

chmod -R 777 /<directory_name>

changes permissions recursively all the files and direcories under parent directory

-chown owner:group <file_name>

changes owner and group for the file_name

Similarly  chown -R owner:group /<directory>

changes ownership/group recursively all the files and direcories under parent directory

-rsh <server_name>

-rsh -l <login_name> <server_name>

-rcp file1 file2

accessing remote servers (This requires pre-configuration on remote servers like .rhosts and hosts.equiv)

-gunzip <file_name>

-unzips file name

-gzip <file_name>

-zips file_name

-compress <file_name>

compresses file_name  (gzip/compress uses different algorithm for (compression)

-uncompress <file_name>

-uncompresses file_name

-pack <file_name>

-unpack <file_name>

packs/unpacks file_name

All the above can be used on directory for compression

which <file_name>

shows if the file_name/command exists and if exists where its path is

-bc -l

bench calculator

-ulimit

shows the size of file, time, memory etc available for current shell

-man <command_name>

gives help/man pages of command given

write <user_name>

you can write messages to the logged in users on the server

-wall

this command writes/sends messages to all users logged in (useful while shutting down m/c)

-fuser -k /dev/pts/2

kills terminal pts/2 and closes its connection

-nohup <command_name> &

-nohup is very useful command. it runs the command even the telnet connection is closed/broken.

& is used for running command in background.

-crontab -l

shows the cron jobs running/scheduled for the current user.

you can copy/redirect the jobs to a ascii file and edit/add jobs and resubmit to cron as

-->$crontab -l > present_cronjobs

-->edit/add entries to present_cronjobs

-->$crontab present_cronjobs  (This will submit/resubmit the jobs in file presnt_cronjobs to CRON)

-at

at is very useful command for running jobs at later time

like

at <time> command/script (will run the script at specified time)

at -l will show the at jobs scheduled

killing an unwanted process

$ps -ef|grep <process_name> (will show the PID of the process in the 2nd field)

$kill -9 <PID>

-who -b

shows when the system has booted

-$uptime

will show how long the system has been up and also shows cpu load, number of users logged in etc.

-last

will show the users logged in/out information

last <user_name>  shows particular user logins/logouts

last reboot shows all the system boots

-id

shows current user's UID, username and GID and group name

hostid

shows unique identifier of host

 more /etc/passwd

it will show all the logins, home directories of the users.

   -more /etc/shadow

shows password encryption info and other user related info (only root has access to this file)

  - more /etc/system

this file has all n/w, h/w, memory etc tunable parameters/values

-more /etc/inittab

after the bootup checks this file for which runlevel to enter

-find / -name <file_name> -print

for finding any file name. ( giving '/' will find files from root directory)

-hostname

will give your system name.

-uname -a

will show system name, solaris version, platform and some more information

useradd

will add user (u have to root user to do this)

it has more options for specifying home directory, shell group etc.

Similarly userdel deletes username

-df -k

will show all the mounted filesystems.

-mount

will show all mounted file systems with additional info like large filesystem support etc

-pkginfo

Gives/shows info about installed packages/software on system

-showrev -p

shows all patches installed on system

-init 0

will shutdown the system

- init 6

will reboot the system (other init options are 1, 2, 3, 5 and S)

-cd /var/adm

this directory has system/application logs. Please check all the files and its contents for more information.

-cd /etc/rc.d

there will be more of this kind.

rc2.d, rc3.d, rc0.d, rc5.d, rc6.d etc...

each directory has scripts which will run in its own run level.

a run level is nothing but the init option u give while starting or stopping the system

suppose you give init 0, system will check in /etc/rc0.d for all the files to be executed.

-/usr/sbin/ifconfig -a

will show the ip-address of the system.

lo0  : loopback interface

hme0 : hundred MBPS n/w interface

qfe0 : quad ehternet interface

-ping <hostname>

will ping and test connectivity between your system and the hostname you give in the ping.

you can also give ping <ip-address>

- rm -r <directory>

will delete all the contents in the directory specified recursively (BE CAREFUL WHILE GIVING THIS COMMAND)

alias l='ls -l'

alias dir='ls -l|grep "^d"'

alias p='pwd'

alias c='clear'

Short cuts for commonly used commands

-tar -cvf allfile.tar /<directory_name>   copies all files under directory to allfile.tar

-tar -xvf allfile.tar    /home     retrieves tar files to /home directory

-tar -tvf allfile.tar   reads contents of allfile.tar

-find . -type f -print -exec grep -i <type_ur_text_here> {} \;

this is recursive grep

-rm - <-filename>

for deleting special files

Ex:-

# ls -l

total 16

-rw-r--r--   1 root     other         13 Dec 24 14:57 -k

# rm - -k

# ls -l

total 0

#

-rm "<file name>"

delete file names with spaces in between

 #######VERY IMP #########

for checking sun related h/w conf.

-top --- shows all process and memory, cpu etc utilisation

-prtconf  -- shows h/w, cpu, memory conf

-mount   -- will show the disks mounted and all partitions

-cd /usr/platform/sun4u/sbin/prtdiag -v  --- shows additional configuration of -memory, cpu speed etc..

-sysdef -- shows system h/w, memory, and other internal configurable/tunable --paramters

-ifconfig unplumb hme0   --- will disable ehternet interface hme0

-ifconfig plumb hme0                 --- will enable hme0

for performance monitoring and diagnosing bottlenecks

-iostat             -- disk utilisation, cpu, io wait etc (iostat -xcM gives --extented statistics of disk activity, cpu etc)

-vmstat          -- memory and virtual memory utilisation

-sar                   -- system archive report, gives total system report for -cpu, memory, disk, etcc

-netstat           --- shows network statistics, like how many connected on ---which services/ports

-mpstat          -- shows multi cpu statistics like load on each cpu.

-psrinfo           -- gives processor/s information (online/offline)

-nfsstat          --- nfs mounted filesystems statistics

-prstat            --- shows process related statistics (present from solaris 2.7 and above)

for disk configurations u need ---

-format -- will show all the disks configuration and partitions

-prtvtoc -- shows disk partition/geometry info

-mkfile 60m jithendra

creates a filename of size 60mb which can be used for adding to swap space

-swap -a jithendra

attaches the 60mb file to swap space (Very useful when swap space is running out)

-swap -l

lists the swap contents

-sleep 5

waits for 5 seconds (useful in shell scripts)

-cat <file_name> |awk '{print $1}'

Prints the first field of the filed ($1, $2... can be used to display more fields)

 :1,$s/<old>/<new>/g

use the above for global replacement of text in ascii files using vi editor

 :1,$s/^M//g

remove Ctrl M character in text files using vi editor

-isainfo -v

shows supported platforms (32-bit, 64-bit)

strings <file_name>

shows printable strings in any type of file (binary, object, text etc)

-truss -p <PID>

-shows system calls and signals (useful when debugging process)

- stty erase ^H

sets backspace for deleting typed character

-echo $TERM

shows terminal type like vt100, vt220 etc.

($PATH, $ORACLE_HOME etc can be used with echo)

-set -o vi

While your shell is set to KSH use this command to display history of commands you are typing

Press ESCAPE and k for showing previous commands

env

shows all the environmental variables set to your current session