Linux Basic Commands

1) How to find Red Hot Linux Version:

cat /etc/redhat-release

cat /etc/os-release

cat /etc/issue

$ hostnamectl

2) How to find my redhot 32 or 64 bit:

You can also do uname -i

Yours will probably respond with i386 for 32bit

If you had a 64 bit version of the OS installed, it would respond with x86_64

3) Wget comands examples:

$ wget http://www.cyberciti.biz/here/lsst.tar.gz

$ wget ftp://ftp.freebsd.org/pub/sys.tar.gz

$ wget -O output.file http://nixcraft.com/some/path/file.name.tar.gz

$ wget http://www.kernel.org/pub/linux/kernel/v2.6/testing/linux-2.6.36-rc3.tar.bz2

4) Use ssh to login to your remote servers without using a password:

--Step 1: Generate a public and private key pair

$ ssh-keygen -t rsa

Generating public/private rsa key pair.

Enter file in which to save the key (/Users/al/.ssh/id_rsa):

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /Users/al/.ssh/id_rsa.

Your public key has been saved in /Users/al/.ssh/id_rsa.pub.

The key fingerprint is:

6f:16:29:90:46:b6:88:34:3d:81:07:fc:bd:1a:fc:db al@Al-Alexanders-MacBook.local

The key's randomart image is:

+--[ RSA 2048]----+

| .++..o          |

| .oo++ o         |

|  .o.o=          |

|    ....   .     |

|   .   .S o      |

|    o .  o .     |

|     +    +      |

|    . .. o       |

|      ..E        |

+-----------------+

As you can see from the output of this command:

Your private key is in a file named ~/.ssh/id_rsa

Your public key is in a file named ~/.ssh/id_rsa.pub

--- Step 2: Copy the ssh keys to all the nodes:

ssh-copy-id usename@

--- Step 3: Test ssh to machine_hostname, it should not ask password:

ssh-copy-id localhost

5) How to login sudo user with out giving password:

visudo (Add a line as below)

root ALL =(ALL) : ALL

username ALL=(ALL) NOPASSWORD: ALL

su - username

then now its comes from  root user to my username

6) How to Use Pscp to Transfer/Copy Files to Multiple Linux Servers:

pscp – is utility for copying files in parallel to a number of hosts.

prsync – is a utility for efficiently copying files to multiple hosts in parallel.

pnuke – it helps to kills processes on multiple remote hosts in parallel.

pslurp – it helps to copy files from multiple remote hosts to a central host in parallel.

Let’s create a new file called “myscphosts.txt” and add the list of Linux hosts IP address and SSH port (default 22) number as shown.

192.168.0.3:22

192.168.0.9:22

# pscp -h myscphosts.txt -l User_name -Av wine-1.7.55.tar.bz2 /tmp/

OR

# pscp.pssh -h myscphosts.txt -l User_name -Av wine-1.7.55.tar.bz2 /tmp/

Warning: do not enter your password if anyone else has superuser

privileges or access to your account.

Password:

[1] 17:48:25 [SUCCESS] 192.168.0.3:22

[2] 17:48:35 [SUCCESS] 192.168.0.9:22

Explanation about the options used in the above command.

-h switch used to read a hosts from a given file and location.

-l switch reads a default username on all hosts that do not define a specific user.

-A switch tells pscp ask for a password and send to ssh.

-v switch is used to run pscp in verbose mode.

7) How to get Weblogic Version :

-- Command line: registry.xml

-- java -cp WLS_HOME/wlserver_10.3/server/lib/weblogic.jar weblogic.version

-- From Admin console:

Login to WebLogic Administration Console and navigate to Servers –> AdminServer –> Monitoring tab        

here it will shows , 1. Weblogic version 2. jdk vendor and version 3. OS name and version

8) How to get the Java Version:

--java -version

java version "1.6.0_16"

Java(TM) SE Runtime Environment (build 1.6.0_16-b01)

Java HotSpot(TM) Server VM (build 14.2-b01, mixed mode)

java version "1.7.0_51"

OpenJDK Runtime Environment (rhel-2.4.4.1.el6_5-x86_64 u51-b02)

OpenJDK 64-Bit Server VM (build 24.45-b08, mixed mode)

9) How to Replace a string in Linux and VI Editor?

sed "s/oldstring/newstring/g" filename and sed :%s/oldstring/newstring/g

10) How to display TOP 10 disk space files?

du -sh* | sort -nr|head -10

11) tar -cvf filename.tar file1 file2 file3

How to extract tar.bz2 files: tar jxvf filename.tar.bz2

How to create tar.bz2 files: tar jcvf filename.tar.bz2 file1 file2 file3

TAR.BZ2

This format has the best level of compression among all of the formats I’ve mentioned here.

But this comes at a cost – in time and in CPU. Here’s how you compress a directory using tar.bz2:

# tar -jcvf archive_name.tar.bz2 directory_to_compress

# tar -jxvf archive_name.tar.bz2 -C /tmp/extract_here/

12) tar -xvf filename.tar

13) tar -zcvf filename.tar.gz file1 file2 file3 , tar -zxvf filename.tar.gz

14) Apache --- httpd.conf , ssl.conf and mod_wl_22.so

15) OHS --- mod_wl_ohs.conf , mod_wl_ohs.so

16) How to take the Thread dump if server in hand state:(Server Hang)

1. ps -ef | grep java

kill -3

2. Weblogic.Admin utilities

java weblogic.admin t3://localhost:7001 -username=weblogic -password=weblogic123 THREAD_DUMP

3. From Admin Console: Server-> Monitoring-> threads -> click on Dump Thread Stuck.

4. WLST

connect('weblogic','weblogic123','t3://localhost:7001')

cd ('servers')

cd ('AdminServer')

Thread dump()

disconnect()

exit()

17) Server crash:

Resongs:

1. Native IO

2. SSL Native Libraries

3. JVM

4. Supported Configuration

5. JDBC driver issue

Analysis:

1. hr_err_p*.log

2. pmap core or pstack

3. debugger mode enable

1. From Admin console :

Environment -> Cluster ->name ->Configuration -> Server Start Sub-tab ->Arguments

2. Copy the existing startWebLogic.sh script to a new script file, startWebLogic_Debug.sh.

JAVA_OPTIONS="-Xdebug -Djava.compiler=NONE -Xnoagent -Xrunjdwp:transport=dt_socket,server=y,address=10171,suspend=n $JAVA_OPTIONS"

18) Symbolic Links

$ ln -s {source-filename} {symbolic-filename}

s means symbolic link  not hard link

ln -s /etc/httpd/vhosts/example.com /etc/httpd/sites-enabled/example.com

unlink {symbolic-filename}

unlink  /etc/httpd/vhosts/example.com

19) Examples of RPM Commands in Linux:-

1- How to Check an RPM Signature Package

# rpm --checksig pidgin-2.7.9-5.el6.2.i686.rpm

2- How to Install an RPM Package

# rpm -ivh pidgin-2.7.9-5.el6.2.i686.rpm

3- How to check dependencies of RPM Package before Installing

# rpm -qpR BitTorrent-5.2.2-1-Python2.4.noarch.rpm

4- How to Install a RPM Package Without Dependencies

# rpm -ivh --nodeps BitTorrent-5.2.2-1-Python2.4.noarch.rpm

5- How to check an Installed RPM Package

# rpm -q BitTorrent

6- How to List all files of an installed RPM package

# rpm -ql BitTorrent

7- How to List Recently Installed RPM Packages

# rpm -qa --last

8- How to List All Installed RPM Packages

# rpm -qa

9- How to Upgrade a RPM Package

# rpm -Uvh nx-3.5.0-2.el6.centos.i686.rpm

10- How to Remove a RPM Package

# rpm -evv nx

11- How to Remove an RPM Package Without Dependencies

# rpm -ev --nodeps vsftpd

12- How to Query a file that belongs which RPM Package

# rpm -qf /usr/bin/htpasswd

13- How to Query a Information of Installed RPM Package

# rpm -qi vsftpd

14- Get the Information of RPM Package Before Installing

# rpm -qip sqlbuddy-1.3.3-1.noarch.rpm

15- How to Query documentation of Installed RPM Package

# rpm -qdf /usr/bin/vmstat

16- How to Verify a RPM Package

# rpm -Vp sqlbuddy-1.3.3-1.noarch.rpm

17- How to Verify all RPM Packages

# rpm -Va

18- How to Import an RPM GPG key

# rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

19- How to List all Imported RPM GPG keys

# rpm -qa gpg-pubkey*

20- How To rebuild Corrupted RPM Database

[root@tecmint]# cd /var/lib

[root@tecmint]# rm __db*

[root@tecmint]# rpm --rebuilddb

[root@tecmint]# rpmdb_verify Packages

rpm –ivh httpd-2.4.x-1.i686.rpm

rpm –Uvh httpd-2.4.x-1.i686.rpm

20) find – search for files in a directory hierarchy                 

        Usage: find [OPTION] [path] [pattern]                    

        eg. find file1.txt, find ­name file1.txt

21) history – prints recently used commands                         

         Usage: history  

22) 3 types of file permissions – read, write, execute

• 10 bit format from 'ls ­l' command

                 1             2 3 4      5 6 7     8 9 10

             file type    owner     group    others

eg. drwxrw­r­­   means owner has all three permissions,

              group has read and write, others have only read             

  permission

• read permission – 4, write – 2, execute ­1    

        eg. rwxrw­r­­   = 764

              673    =   rw­rwx­wx

23) chmod – change file access permissions                                          

       Usage: chmod [OPTION] [MODE] [FILE]                               

      eg. chmod 744 calculate.sh   

24) chown – change file owner and group                                              

      Usage: chown [OPTION]... OWNER[:[GROUP]] FILE...        

      eg. chown remo myfile.txt

25) du – estimate file space usage                                                           

     Usage:  du [OPTION]... [FILE]...                                                

     eg. du -sh  

26) df – report filesystem disk space usage                                            

    Usage: df [OPTION]... [FILE]...                                                   

    eg. df -h 

  

27) quota – display disk usage and limits                                              

    Usage: quota [OPTION]                                                               

    eg. quota ­v   

28) reboot – reboot the system                                                     

       Usage: reboot [OPTION]                                                 

     eg. reboot                                                                          

                

29) poweroff – power off the system                                           

       Usage: poweroff [OPTION]

     eg. poweroff 

30) locate – find or locate a file

     Usage: locate [OPTION]... FILE...

     eg. locate file1.txt

31) File Commands

------------------

ls – directory listing

ls -al – formatted listing with hidden files

cd dir - change directory to dir

cd – change to home

pwd – show current directory

mkdir dir – create a directory dir

rm file – delete file

rm -r dir – delete directory dir

rm -f file – force remove file

rm -rf dir – force remove directory dir *

cp file1 file2 – copy file1 to file2

cp -r dir1 dir2 – copy dir1 to dir2; create dir2 if it

doesn't exist

mv file1 file2 – rename or move file1 to file2

if file2 is an existing directory, moves file1 into

directory file2

ln -s file link – create symbolic link link to file

touch file – create or update file

cat > file – places standard input into file

more file – output the contents of file

head file – output the first 10 lines of file

tail file – output the last 10 lines of file

tail -f file – output the contents of file as it

grows, starting with the last 10 lines

32) Process Management

-----------------------

ps – display your currently active processes

top – display all running processes

kill pid – kill process id pid

killall proc – kill all processes named proc *

bg – lists stopped or background jobs; resume a

stopped job in the background

fg – brings the most recent job to foreground

fg n – brings job n to the foreground

33) File Permissions

-------------------------

chmod octal file – change the permissions of file

to octal, which can be found separately for user,

group, and world by adding:

● 4 – read (r)

● 2 – write (w)

● 1 – execute (x)

Examples:

chmod 777 – read, write, execute for all

chmod 755 – rwx for owner, rx for group and world/others

For more options, see man chmod.

34) System Info

--------------------

date – show the current date and time

cal – show this month's calendar

uptime – show current uptime

w – display who is online

whoami – who you are logged in as

finger user – display information about user

uname -a – show kernel information

cat /proc/cpuinfo – cpu information

cat /proc/meminfo – memory information

man command – show the manual for command

df – show disk usage

du – show directory space usage

free – show memory and swap usage

whereis app – show possible locations of app

which app – show which app will be run by default

35) Compression

-------------------------

tar cf file.tar files – create a tar named

file.tar containing files

tar xf file.tar – extract the files from file.tar

tar czf file.tar.gz files – create a tar with

Gzip compression

tar xzf file.tar.gz – extract a tar using Gzip

tar cjf file.tar.bz2 – create a tar with Bzip2

compression

tar xjf file.tar.bz2 – extract a tar using Bzip2

gzip file – compresses file and renames it to file.gz

gzip -d file.gz – decompresses file.gz back to        file

36) Network

------------------------

ping host – ping host and output results

whois domain – get whois information for domain

dig domain – get DNS information for domain

dig -x host – reverse lookup host

wget file – download file

wget -c file – continue a stopped download

37) Installation

---------------------

Install from source:

./configure

make

make install

dpkg -i pkg.deb – install a package (Debian)

rpm -Uvh pkg.rpm – install a package (RPM)

38) SSH

---------------------

ssh user@host – connect to host as user

ssh -p port user@host – connect to host on port

port as user

ssh-copy-id user@host – add your key to host for

user to enable a keyed or passwordless login

39) Searching

-------------------

grep pattern files – search for pattern in files

grep -r pattern dir – search recursively for

pattern in dir

command | grep pattern – search for pattern in the

output of command

locate file – find all instances of file

40) Shortcuts

--------------------

Ctrl+C – halts the current command

Ctrl+Z – stops the current command, resume with

fg in the foreground or bg in the background

Ctrl+D – log out of current session, similar to exit

Ctrl+W – erases one word in the current line

Ctrl+U – erases the whole line

Ctrl+R – type to bring up a recent command

!! - repeats the last command

exit – log out of current session        

41) vmstat

vmstat reports virtual memory statistics and is used to help identify performance bottlenecks

vmstat reports information about processes, memory, paging, block IO, traps, disks and cpu activityactivity.

vmstat syntax: vmstat [options] [delay [count]]

$ vmstat

procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------

r  b   swpd   free   buff  cache   si   so    bi    bo   in cs us sy id wa st

0  0 305416 260688  29160 2356920   2    2     4     1    0  0  6  1 92