1.Shell :
Operating system to User intermediate
#cat /etc/shells
/bin/sh => Shell
/bin/bash => Bourn Again Shell
/bin/tcsh =>
/bin/csh => C Shell
/bin/nologin => NoLogin shell
2. Kernel :
Hardware to Operating system monitoring
3. [Root@Server6 ~]# or $ :
Root => Indicate to which User
Server6 => Indicate to Hostname
~ => Indicate to Home Directory
# => Indicate to Root Privilege
$ => Indicate to Normal User Privilege
4. F.S.H ( File System Hierarchy ) :
/root => Root Home Directory
/boot => Only stored Boot files
/home => Normal users Home Directory
/bin => Stored in Binary files or Executions files
/lib => Library files or Documentations
/etc => All Configuration files stored in this directory
/var => Variable Directory. Used to share the contents ( FTP, HTTP�)
/mnt => Used to default mount point for Disk Partitions
/media => Mount Point for External Devices ( CD/DVD, USB, Pendrive�)
5. Help and Information for Commands :
MAN => Format and Display online manual copy.
# man ls
# man mkdir
INFO => Read full Documentations.
# info ls
# info cd
PINFO => Small Graphical Page.
# pinfo ls
# pinfo cd
--HELP or -? => Small Information.
# ls �help
# ls -?
WEBPAGE => It display webpage Documentations.
6. LS Command :
Options : -l => Long List
-a => Display All Files.
-d => Display Present Directory Information
-h => Human Readable.
-f => Display File Type.
-R => Display sub directory to recurs.
# ls �alh
# ls �R
# ls �d .
7. PWD Command : ( Present Working Directory )
# pwd
/root.
8. WHOAMI Command : ( To identify which user login for Terminal)
# whoami # whoami
Root. Shyam.
9. LOGNAME Command : (The real user who logs in initially)
# logname # su - shyam
Root. # logname
# whoami Root.
root $ whoami
shyam
10. HOSTNAME Command : ( to check the computer name )
# hostname
Server6.
11. UNAME Command : (to check OS, Version, Architecture, Hostname etc..)
Options : -a, -s, -n, -r, -v, -m, -p, -I, -o
# uname
Linux.
#uname �a ( all )
Linux server6.example.com 2-6.32-131.0.15.el6.x86_64 ��������
12. CD Command : ( to use Change Directory )
# cd => go to home directory
#cd ~ => go to home directory
# cd /var/www/html/ => go to html directory
#cd .. => back to one directory
#cd - => forword to directory
13 ID Command : ( Identification, to check UID and GID )
# id
Uid=0(root) gid=0(root) groups=0(root)
# id shyam
Uid=500(shyam) gid=500(shyam) groups=500(shyam)
14. TTY Command : (Psuedo Terminal, to check the user login and terminal)
Terminal 0 :
# tty
/dev/pts/0
Terminal 1 :
#tty
/dev/pts/1
15. CLEAR Command : ( to clear the terminal screen )
# clear
16. DATE Command : ( Display the Date and Time )
# date => to display date and time
# date �s 2011-12-05 => change only date
# date �s 5:30:20 => change only time
17. CAL Command : ( Display the Calendar )
# cal => to display current month
# cal 2011 => to display 2011 an all month
# cal 12 2011 => to display month 12, year2011
18. WHICH Command : ( Show the full path of commands/shell)
# which ls
/bin/ls
#which chown
/bin/chown
19. WHATIS Command : ( Search the full database for complete words )
# whatis w
Who is logged on and what they are doing
#whatis ls
20. WHEREIS Command : ( Locate the Binary, Source, Manual page for all commands)
# whereis ls
Ls: /bin/ls /usr/share/man/ma1/ls.1.gz /usr/share/man/man1p/ls.lp.gz
21. WALL Command : ( Broadcast on the message send to all logged in user on the system)
# wall
Hai Pls reboot. => type the msg.
CTRL + D => Exit
22. WC Command : ( Word Count, word counting cmd)
Options : -l => line count , -w => word count, -c => byte count, -m => character count
# wc �l /etc/passwd
# ls | wc �l
23. TOUCH Command : ( to create Empty File or 0byte file )
# touch file1
# touch /home/shyam/shyam.txt
# touch file{1..5}.txt
# touch file1 file2 file3 file4 file5
24. CAT Command : ( Canonical system )
# cat file1 => show the file1
# cat > newfile1.txt => create new file.
# cat >> newfile1.txt => overwrite new content
25. HISTORY Command : ( to shows the all typed commands )
# history
# ! serv => to run service httpd restart
# !55 => to run 55 command
26. MKDIR Command : ( Make Directory )
# mkdir test => create directory under the PWD
# mkdir /var/www/html/pc1.linux.com/ => create to directory under the html.
27. MORE Command : ( It shows small paragraph )
# more /etc/httpd/conf/httpd
#more /etc/passwd
28. LESS Command : ( it display simple method, scrolling function available)
# less /etc/httpd/conf/httpd
# less /etc/passwd
29. HEAD Command : ( it shows 1stfew lines of the text, By default 10 line )
# head /etc/passwd => By default 1st 10 line
# head -5 /etc/passwd => to display 1st 5 lines
# head -20 /etc/passwd => to display 1st 20 lines
30. TAIL Command : ( it display last few lines of text, By default last 10 line )
# tail /etc/passwd => By default last 10 lines
# tail -15 /etc/passwd => to display last 15 lines
# tailf /var/log/httpd/access_log => view log files while it is being updates
31. UNIQ Command : ( Identify any duplicate line entries in a file or input provider )
Options : -d , -i
# vim shyam.txt => type any content
# uniq shyam.txt =. To check
32. STRING Command : (Find and Display legible information embedded within a non-text or binary file)
# string /bin/cat
# string /bin/mkdir
33. CP Command : ( Copy File, Copy the file/Directory one location to another location as same copy )
Options : -I, -r, -p
# cp shyam.txt shyam.txt.back => take the copy and change the name
# cp shyam.txt /var/ftp/pub/shyam.txt => copy to another location
# cp /root/shyam.txt /var/ftp/pub/shyam.txt => same as above, it is another method
# cp �I /root/abc.txt /tmp/abc.txt => copy time ask Yes or No
# cp �p /root /abc.tcxt /tmp/abc.txt => permission, time, ownership copy to same
# cp /root/* /tmp/ => copy all
# cp /root/.txt /tmp/ => only copy .txt contents
# cp �r /root/* /tmp/ => copy at recursive
34. MV Command : ( Used to Move / Rename the file or directory )
# mv /root/shyam.txt /root/aaa.txt => rename the file
# mv /root/shyam.txt /var/ftp/pub/shyam.txt => move the file to another location
35. RF Command : ( Remove the File / Directory )
Option : -f => Force, -r => Recursive
# rm shyam.txt => Remove the file
# rm �f shyam.txt => Remove the file forcibly
# rm �r shyam.txt => Remove the file and ask the Yes or No
# rm �rf shyam.txt => Forcibly removing
36. STAT Command : ( File/Directory Statistics or Properties)
# stat /root
# stat/root/shyam.txt
37. File / Directory Attribute Settings :
lsattr => Listing , chattr => Modifying ( + set the value, - Unset the value )
Options : -a, -i,�.
# lsattr /root/shyam.txt
-----------e- shyam.txt
#chattr +ia shyam.txt
------ia----e- shyam.txt
#chattr -ia shyam.txt
------ia----e- shyam.txt
38. Pattern Matching : GREP ( Global Regular Expression Print )
# grep �shyam� /etc/passwd
Shyam:X:500:500: :/home/shyam:/bin/bash
# grep �shyam� - -color /etc/passwd
# grep �root� /etc/passwd /etc/shadow
/etc/passwd => root:X:0:0:root:/bin/bash
/etc/shadow => root: :15253:0:9999:7: : :
# grep ^root /etc/passwd => ( to display startins word for root all entries )
# grep bash$ /etc/passwd => ( to display last word or sentence )
# grep ^root$ /etc/passwd
# grep �i shyam /etc/passwd => ( to ignore all letters)
# cut �f2 �d � : � /etc/shadow
# grep �shyam� /etc/shadow
# grep �shyam� /etc/shadow | cut �f2 �d � : �
39. Symbols :
� => Overwrite the file�s
>> => Appending the file�s
| => Pipe
&& => AND Option 1st is true then go to 2nd option
|| => OR any one condition is true
40. USER Administration :
UID : 0 => root, 1 to 499 => System Services, 500 above => Normal Users
User Account file and Directory :
/etc/passwd, /etc/shadow, /etc/groups, /etc/gshadow, /home/users, /var/mail
1. /etc/passwd : user1: X: 500: 500: Regular Comments: /home/user1: /bin/bash
User 1 => User name
X => Password place holder
500:500 => UID and GID
Comments => Use any Comments, Hai welcome etc�
/home/user1 => User Home Directory
/bin/bahs => User Shell
2. /etc/shadow : user1: $6$BY$JKJJ9789N�: 15265: 0: 99999: 7: : :
User1 => User name
$6$jhvjh�. => Encrypted Password
15265 => Last changes day ( Epoch time Jan 01 1970 )
0 => Minimum days
99999 => Maximum days
7 => Warning days
: => Inactive days
: => Disabled day
: => Feature use
3. /etc/group : user1: X: 500: :
User => User name
X => Password place holder ( /etc/gshadow)
500 => GID (Privet GID )
: => Group members
42. USERADD Command : ( Add a new user )
Option : -c => Comments
-o => non-unique ( to use duplicate UID in normal user )
-u => UID ( we have to prefer UID )
-s => Shell ( to change shell )
- r => system account ( to use system service accounts )
-g => GID ( to use duplicate GID in normal users )
-e => Expire date ( given to the account expire date )
-p => Password ( given to the Encrypted password )
-d => Home Directory ( change to home directory)
# useradd user1 => Normal creation
# userad �c Hai �o �u 605 �s /bin/csh user2 => Add Comments, UID, Shell
# useradd �r user3 => Encrypted Password
# useradd �g 700 -e 2011-11-01 -d /var/www/html/user4 user4 => Add GID, Expir date, Home directory
# useradd -s /sbin/nologin user5 => Use nologin
# passwd user1
1. User Login Information :
# vim /etc/login.defs
2. Default Useradd Functions :
# vim /etc/default/useradd