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 1st
few 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 :
Ø
=>
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
