Redhat Enterpriese Linux Server Administration
Session during installation:-
Ctrl+alt+f1→mai
n installation in text mode (initial)
Ctrl+alt+f2→
shell prompt
Ctrl+alt+f3→
driver insert session.
Ctrl+alt+f4→
result or out put session
Ctrl+alt+f5→
file system related massage
Ctrl+alt+f6→
main instalation in gui
Login session:-
Ctrl+alt+f1
Ctrl+alt+f2
Ctrl+alt+f3
Ctrl+alt+f4
Ctrl+alt+f5
Ctrl+alt+f6
Ctrl+alt+f7
(above are 7 session
means tty . here 6 is in commadn and no.of 7 is in graphical)
Run level :- it is a level which is used to start the pc with
specific service. System provide servics according to run level.
Run level 0 →shutdown
Run level 1→single
usermod (all run level will start bt network connectivity will not.)
Run level 2→full
multiuser mode without nfs
Run level 3→full
multiuer mode in text user interface
Run level 4→unused
Run level 5→full
multiuser mode in gui
Run level 6→rebootWe can choose or execute run level by
#Init
run level no.
(bydefualt system star ts in 3 or 5 run
level)
In place of # if there is $ it shows that
it ordinary user.
|
|
Dos
|
Win.sk3
|
Linux
|
|
To install o/s part.
|
Dos partition
|
Pri/logcial
|
Pro./logical
|
|
Drive (mount point)
|
C:/
|
C:/
|
Main root part.
|
|
File system
|
Fat16
|
Fat 32,ntfs
|
Ext3,ext2
|
|
No. Of part.
|
1,pri
1,extendad
26,logical
|
4 pri/3pri , 1extendad
&logical
|
4pri/3pri. 1ext
Upto 63 logical
|
|
Virtual memory
|
not
|
Auto manage(pagefile.sys
|
Double of ram swap part.
|
|
WINDOWS
|
LINUX
|
|
User friendly o/s
|
Command line o/s
|
|
Graphical user interface
|
GUI/CLI
|
|
Not secure
|
Secure
|
|
.exe
|
Rpm
|
|
Virus attack
|
Virus free
|
|
Vista/2k8
|
Server/client
|
|
Currept
|
Not currupt
|
Linux
distributer:-
Redhat,fedora,suse,debin,coledra,mandriva,knoppix
Note:- linux needs two partition to
install 1, / 2,swap
Virtual memory error display if there is
low space virtual memory. To solve this problem delete some data.
Bootinf file→ kernel file
Windows boot loader →ntldr
Linux boot loader→grub/lilo
GRUB= grand unified boot loader
LILO =linux loader
|
GRUB
|
LILO
|
|
Higher virsion
|
Lo
|
|
/boot/grub
|
/boot/lilo
|
|
Primary/logical
|
Primary
|
|
Any where in HDD
|
1 to 10 GB HDD
|
|
Ssecurity
|
No
|
|
Data recovery easy
|
No
|
|
Presently use
|
Not in use
|
HDD
cylender
In 1 GB 121 cylender
Directory
structure
/→it store all O/S file and directory
/boot→add bootable file and directories
/dev→store all devices information
/home→store all normal user directiries
/root→it is the directory of super user
/tmp→store all temporary file
/sbin→store all super user command
/bin→store all super and normal user
command
/usr→store all help related command
/var→store all variable user
/etc→store all configuration file and
directories
/proc→store all runnig and H/W information
/lib→ store all librery file
/mnt
/opt It’s all use for mounting
/net
/media
/lost+found→ as a recycle bin
Pagefile.sys → virtual memory
HDD sata → /dev/sda
CD –ROM IDE→ /dev/hda
USB
→/dev/sdb
Partition can be
4 primary
3 primary and 1 extended
2 primafry and 1 extended
1 primary and 1 extended
Logical partition get no. 5 bydefault
Exa: /dev/sda5
Installation
of linux
If u r installing through network then set
first device lan
If u installiing through DVD set first
device DVD
AT
BOOT PROMPT
Installation via graphical mode using DVD
Boot:linux text Installation via text mode using DVD
To install via dvd:-
Boot:linux askmethod
(at language option)→English→OK→(at
keyboard type)US→OK→(select ur installation method if ur installing via dvd
then select “local CDROM”)→local CDROM→OK→(now cd found screen appear here u
can select if u want to test ur dvd other wise skip)SKIP→OK→next→skip
installation no→skip→YES→creat custom layout (if u want to create partition
according to ur requirement)→(linux need two partiton /+swap to install o/s / part.must be minimum 8GB and swap is double
of RAM)→ select new option →select mount
point /→ file system ext3→part.size in
MB (8000)→ok→now select new again and file system swap → define siz swap
double of RAM→next→select add if u r
using two o/s on ur pc otherwise select →next→select manuaaly because u r
instaling this o/s via dvd→type ur hostname(irfan.com)→next→selct asia/colcutta→
tupe root passwd (redhat)→custom later→next→next→reboot→forward→forward→disable
firewall→yes→forward→forward→forward→type user name and passwd →forward→finish.
Installation via graphical mode using 5
type
Alt+f3 =====>to check ip of ur machine
and machine which was given by DHCP
Alt+f1=====>to come main window
installation window
Ctrl+alt+f2 ===→ to check RAM
To install linux:- there are many optons
which helps you to install o/s. These option are avaible if u press f1 , f2 ,
f3 ,f4 ,f5. If u are using cd type (linux
askmethod) to install ur o/s
Basic
command :-
#init 0
(to shutdown)
#init 1 (for single user mode without
authentication and without graphical)
#init 2
(for multiuser mode without graphical and NFS)
#init 3
(for multiuser mode with nfs and without graphical)
#init 4
(unsued)
#init 5
(for multiser mode with graphiccal and nfs)
#Init 6
(to restart PC)
# clear (to
clear screen)
#pwd (print
working directory)
#tty to
view run terminal information
#runlevel to
view run level information
#ls (for
list of file and directory)
#ls –ld
data (directory and symlink information)
#ls
-al (deatail of ths
command is as follow)
If in place of d there is – it shows
file b=block file c=charactor
#mount it
shows file system type,permisstion of mount point
#ls –l (list of file and directory)
#ls –al (to
show hidden file and directories also)
#dir (list
of directory and file)
#date (to
show date and time)
#cal (to
show calender)
#cal 2009 (for what year calender)
#history (to
view all runed command)
#history –c (to clear history)
#alias (show
for all alias )
#alias c =clear (set alias for any command like c=clear)
Alias means shortckut
#unalias c (removing
for alias)
#bc (to
show calculator)
To come out type quit
#cd /etc (to
change directory)
#cat filename (for use read file)
head is use to display firtst 10 line
#head
filename
tail is used to display last 10 line
#tail filename
U can also use –n to change number of line
display ex:
#tail
-n 3 /etc/passwd (is used to display last 3 line)
#head
-n 3 /etc/passwd (is used to display first 3 line)
Grep also use to view where a pattern is
matched
#grep ‘irfan’ /etc/passwd
cut display speciic columns of file
#cut
-d: -f1 /etc/passwd
wc
(word count ) is use to count word of a
file
#wc
file name
3 8 38 t
(3=line 8=word
38=size)
Switchs which can b use
Use
-l for only line count
User
-w for only word count
Use –c for only byte count
diff is use to compare two file
#diff file1 file2
Aspell is use to check spelling for file
#aspell check filename
A quick spelling dictonary look up can be
performed with the look command . it comes in handy when need the
spelling of a word fo which u know the firtst few letters
#look exer
(this shows all word which started from exer)
#runlevel (for
use show user level)
#touch filename (to create file)
At a time 7 user can login. 6 in command
mode and 1 in graphical
GUI to CLI ctrl+alt+f1
#tty (to
check terminal number)
#exit
#logout
#ctrl+d
Above three command use to exit or logout
#whoami (t
o check login user name)
#mkdir
directoryname (to create a
directory)
#cat >> filename (to write matter in a file)
#mkdir
irfan irfan1 irfan2 (to
create multiple directories )
#mkdir
-p /a1/a2/a3 to create parant directory {ek k under
doosri}
To copy:-create a directory
#mkdir
/irfan
#cp
-rv /etc /irfan
to copy etc directory in irfan
-rv
means recursivewith subdirectory also
Move and remame command:-
#mkdir
irfan to creat a
directory
#mv
/etc /irfan/myetc (this command will move etc folder in irfan
folder with name of myetc)
#touch file1 file2 file3 (to creaat
multiple files)
#mkdir
irfan{1,2} (create multiple
directoires with irfan suffix)
#touch
irfan{1,2} ((create multiple files
with irfan suffix)
#rm file (to
remove filewith confirmatio)
#rmdir
directory name (to remove empty directory only)
#rm
-f filename (remove file without confimation)
#cp
oldfile newfile (to
copy file)
#cp
dir1 dir2 (to copy
directory)
Dir1 is source and dir2 is destination
#fdisk
-l (to information about HDD)
#df
-h (to view
mounted partition in GB)
#df
-m (to view
mounted partition in MB)
#du
-sh file or directoryname (to check size of file or directory)
To
mount pendrive in linux. (pen drive must be format in fat32)
#mount
/dev/sda1 /mnt (where mnt is a folder whre u want mount
pendrive)
To remove mounted pendrive
#umount
/mnt
To mount cd in linux
#mount
/dev/cdrom /mnt
#cp
-rv Server /mnt (to copy server folder in mnt with
verbose)
#mv
/imp /mnt/vip (to move
imp directory in mnt from vip name)
#free
-m (to check Ram)
#cat
/proc/cpuinfo (informatio
about cpu)
VI stand for
visual stand for visual editror.
#vi
filename (to create a
new file or editing existing file)
Insert (to
write in file)
But there are three typs to come in insert
mode
Esc i to
come in insert mode
Esc s to
delete exist charactor &come in insert mode
Esc a ona
charactor append &come in insert mode
Insert 2time to replace mode
Esc:set
nu to set line number
Esc:set
nonu to remove line number
Esc1yy to copy one line
Esc p to
paste
Esc1cc to
cut one line
(wher e blink ur cursr it is first line
and belove is second and means top to bottom)
Esc1dd to
delete one line
Esc u to
undo
Esc ctrl+r to
redo
Esc:20 to
go on line no.20
Esc/word to
serch any word
Esc n t
o repeat last found
Esc:%s/oldword/newword t o replace any word
Esc y1w to
copy one word
Esc c1w to
cut one word
Esc d1w to
delete one word
Esc:w to
save file
Esc:wq to
save & exit
Esc:wq save
and exit
Esc:q exit
Esc:q! Save
witout save
Esc:wq! Save
and exit
Esc:w
filename to save
as
#vim
-x filename (to protect file by
pasawd)
Esc
ctrl+g to count line no.
Esc/word to
find any word
N to
repeat
Esc
gg move
cursr on top of the file
Esc
shift+g move cursur onat
bottom of the file
Esc :line no. To go specific line no.
Esc x delete
one charactor or
Esc delete key
Esc . to
recall last command
Esc shift+G to go at the end of file
Esc:line no.
To
learn more about vi type vimtutor at command prompt.
#hostname newhostname to set hostname temperary
#vim
/etc/sysconfig/network to set
hostname permanantly
Crontab:-it use for
as a shedule task
#crontab
-l to show crontab detail
#crontab
-u root -l (to
show crontab for root )(whre -u is for
user and root is user name)
#which
commandname to view command
related directory
#crontab
-e to set crontab
Minute hour date month day task
0-59 0-23 0-31 0-12 0-7 /bin/mkdir irfan
0 to 6 (0=Sunday 1=Monday and so on)
#service
crond restart
#crontab
-r to remove crontab
Compression:-
Tar gzip bzip2
Folder/file file file
.tar .gz .bz2
Very low low higher
Tar:- it is used to compress file and
folder and to take backup for file and folder
At first creat a folder
#mkdir
/irfan
Now copy some data
#cp
-rv /etc /irfan
#du
-sh /irfan to view size of irfan folder
#tar
-cvf filname.tar source
Where filename.tar is the file where u
want to take backup and source is the folder which u want to take backup.
#tar
-cvf irfan.tar irfan
Note :- file name must be in .tar
Where c=create v=verbose f=file
Now if delete ur original folder (irfan) u
can restore it
#rm
-rf irfan
#tar
-xvf irfan.tar
GZIP:- it is in built utility in linux to compress file
only not for folder.it is more powerful than tar
#gzip
filename
Ex:
#gzip
irfan.tar
Now
run dir command it will display a file named .gz
#du
-sh irfan.tar.gz
To unzip
#gunzip
filname.gz
#gunzip
irfan.gz
BZIP2:- it is also use for to compress
file only. It is more powerful tham tar and gzip
#bzip2
filename
Now
run dir command it will display a file named .bz2
To unzip bz2
#bunzip2
filename
Disk
management:-
#fdisk
-l to check partition
#fdisk
/dev/sda to create
new partition(Where /sda is ur HDD controller)
→m for
help
→n new
partiotion
→d for
delete
→p for
print partition
→e to
create extended partiotion
→l to
create logical partiotin
partition
no. =3
first cylender value (here enter only)
+size
=cylender
+sizeM =megabyte
+sizeK =kilo
byte
→+1024M to
create one GB partition
→w to
save and exit
→q to
exit without save
Now reboot ur system or run this command
#partprobe
(to reinitialize
partition table to kernel)
#mkfs.ext3
/dev/sda3 (to format ur
partition) where sda3 is partiotion number
If u want to work in this partiotion u
have to mount it
#mount
/dev/sda3 /mnt (to mount ur partition.where /sda3 is
partiotion no. And mnt is a folder where u mounted this partition){but it is
temperary mont if u reboot ur system then parttion will not be monted to mount
permanant you have to entry in
/etc/fstab file.}
# mount
-a (to reinitialize filesystem
table)
#df
-h to check mounted partition
But this mount is temparory to mount
permanant entry this partiton in fstab file
#vim /etc/fstab
|
Source
|
Mount point
|
Filesystem type
|
Access mode
|
f/s option
|
|
/dev/sda5
|
/mnt
|
Ext3
|
Defaults
|
|
T o delete partiotion:-
At first u have to unmount that partition
#umount
/mnt to unmount
ur partition
Now run this command
#fdisk
/dev/sda
→d to
delete
→3 partittion
no. Which u want to delete
→w to
save and exit
Now restart ur PC or run #partprobe
LVM (logical volume manager):-
Perform following four step to resizable
partiotion
1 normal partition
2 physical volume
3 volume group
4 logical volume
Step 1:- create
normal partiton
A , create single normal partition (size=2000MB
/dev/sda4)
B,
change part. Id 8e (linux lvm. To change id type t.for id list type l)
C, save partition table and run #partprobe
Step2:- create
physical volume
A, to create physical volume
#pvcreate
<partition no.>
Ex: pvcreate /dev/sda4
Physical volume /dev/sda4 successfully
created
#pvdisplay to display information about pv
Step3:- create
volume group
A, to
vg
#vgcreate
vgname pvname
Ex: #vgcreate india
/dev/sda4
Step4:- create
lv
A, to create lv
#lvcreate
–L +sizeM -n
lvname vgname
Ex: #lvcreate -L
+800M -n indore
india
#lvdisplay to show information about lv
Now we can format and monut this
partition.
Step5:-
now we can extend lv
A, to extend lv
#Lvresize
-L +sizeM lvname
# Lvresize -L
+400M lvname
Logical volume /dev/india/indore
successfully resize 2400M
#lvdisplay to
show information aboun lv
{#lvextend –L +500M
lvname to extend lv size}
{#lvreduce
-L -300M lvname
to reduce lv size}
B, if this lv is mounted then we have to
run following command to online update LV.
#resize2fs lvname
#df
-h to check
Step6:- to
extend VG
A, repeat step1 and step2
B, to extend partiton
#vgextend
vgname pvname
#vgdisplay to
information about vg
Removing
LVM
Firtst umount lv
#umount
lvname
#lvremove
lvname to remove lv
Now remove vg
#vgremove to
remove vg
Then remove pv
#pvremove to remove pv
Now u can delete normal partition from
fdisk command
RAID
:- redundent array of inexpensive disk
Simple volume:- one hdd require no faults
tolerence.
Spanned volume:-two hdd require and no
fault tolerence becuase if one hdd fail
second also fail.
Stripped volume:- (raid 0 ) two hdd
require and no faults tolerence provide.
Mirror volume (raid 1) :- 2hdd require
100% fault tolerence.
Stripped set with parity:- (raid 5) 3hdd require 100%
fault tolerence.
Raid :- it is a technology that allw hig
level of storage reliabilty
Ther e are two types of raid
1.software based 1, hardware base
Volume= stripped 0
=mirrored 1
=stripe
with RAID 5
Id
=fd
#fdisk
-l
#fdisk
/dev/sda
→n new
partition
==:
here enter only
+200M
t to
change id
4 partition
no.
Fd id
P print
the
Make another new partition
With same size and same id
W to
save and exit
Now reboot or run #partprobe
#mdadm
-C /dev/md0 -l 1
–n 2 /dev/sda{4,5}
Where
Mdadm=for create vome, -C=create,
-l=level raid, 1=mirrored, md0=to create one part. From two, 2=part.no, /dev/sda{4,5}=partition no.
This command use to create a volume like
mirror or striped etc.
#watch
cat /proc/mdstat to check raid process
Ctrl+c
to exit from this
#mkfs.ext3
/dev/md0 (format md0 is also
formatted both parttition)
#mount
/dev/md0 /mnt to mount
#df
-h to check
#cd
/mnt
#mkdir
1{irfan,raja,irfanu}
#ls
#cd
/
Now if u fail or remove one partition then
we will get data from another part.
#mdadm
--manage /dev/md0 --fail
/dev/sda4
#watch cat
/proc/mdstat
#cd
/mnt
#ls
If u want to add new partition and if u
want mirrer it then
#mdadm
-S /dev/md0 to stop raid service
#mdadm
--manage /dev/md0 --add
/dev/sda6 to add part.in raid md0
#mdadm
--manage /devmd0 --remove /dev/sda4 to
remove part. Frome raid md0
If u want to remove part. Then u have
unmount it and then delete from fdisk.
Network configuration:-
#/sbin/ip a (to view all active devices)
Link command is user to web browser
#links http://www.redhat.com (it is use when ping command is blocked or u
don,t remember full path of url)
#ifconfig to
view ip add. Subnetmask,mac,
#ifconfig
eth0 to view detail about
only eth0
#ifdown
eth0 to down eth0
#ifup
eth0 to up eth0
#route
-n to view gateway
#neat-tui to
change ip subnetmask gateway
#service network restart to active new ip setting
#ping
1.1.1.1 for check conectivity
#mii-tool to
check network cable
#ethtool
eth0 to check cable link
#cd
/etc/sysconfig/network-scripts/iftab this file store all
network setting
#ls
#vim
/ifcfg-eth0 user for change
setting of network then save and exit
#system-config-network to change ip setting
#setup it
is also use to chang network
#hostname to
view hostname
#hostname
irfan.com to change hostname
#system-config-network-tui to change tcp/ip setting
#service network restart to take effect of new setting
#service network status to check status of service
To
make multiple interface permanantly:-
#System-config-network-tui →(add new
device and set name ex: eth0:1 and set ipadd.and subnetmask)
#nslookup
station22.example.com to query
with dns via hostname
#nslookup
172.24.254.254 to query with dns via ip add.
#vim
/etc/sysconfig/network-scripts/ifcfg-eth0 to
set permanent ip add. Then run #servicce network restart.
Passwd breaking:- press up and
down arrow key to select which entry is highlited(at red screen).press ‘e’ on
redhat linux server. Select following line
Kernel /boot/vmlinuz-2.6.18-128.el5 ro
root=LABEL=/ rhgp quiet
And press ‘e’ →press space buton →type 1 or s to start pc
with single user mode →press ‘b’ to pc→
Sh-3.2#passwd root (type new root passwd and start pc with runlevel 3)
User management:-
Follwing file are able to save user’s
information
# vim /etc/shaow
#vim
/etc/passwd
#vim
/etc/group
User’s defaults home directory will be
“/home/user’s name
Ex: for user irfan =/home /irfan
#vim
/etc/shadow (this file store the user’s passwd & accout passwd aging
information)
#vim
/etc/passwd (this file store’s the
user id no.home directory group id no.and shell prompt information)
#vim
/etc/group (this file store on ly
group related information)
#vim
/etc/login.defs (to set default
passwd and account policy for user and group)
#vim
/etc/default/useradd (to
change home directory for user)
#chmod
usernmae (to change user accout and passwd age)
#chage
-l username (to check list)
#adduser
username OR # useradd username to add new user
#passwd username to set passwd for user
Note:- if u don’t type username it will
change root passwd.
#usermod
-L username to lock user
#usermod
-U username to unlock user
#cat
/etc/shell to
use only show shells
/bin/sh = system use
/bin/bash
=for user
/sbin/nologin= for no login user
#chsh
-s /sbin/nologin username to
change shell for user . now user will not login.
#chsh
-s /bin/bash username to
change shell for user . now user will login.
Note:- if u will not type username it will
change shell for root.
#groups to
view group
#groupadd
groupname to
add group
Group level
Primary group:- -g
single
Secondary groups:- -G
multiple
#adduser
-g groupname username to add new user in existing group.
#adduser
-g primary group name -G
secondary group name username (to add new user in existin mutipl groups)
#groups
usernme to check users groups
#usermod
-g groupname username to add existing user in existing group.
#usermod
-g primarygroupname –G
secondarygroupname username (to
add existing user in existing multiple group)
#groupdel
groupname to delete group
#userdel
-r username to delete user
(if
-r will not use it then will user’s home directory will not remove)
#usermod
-G group1 group2 username to add existing user in
multipe exsitting groups
#passwd
-d username to remove login time passwd
#Id to
view root id (root defatult id is zero)
#id
username to view user id
User
permission:-
These all tasks will be in /
#mkdir
/data
#ls
-ld /data to
view permission on data folder
#groupadd
india add a new group
#adduser
-g india a1 (a1 is user name)to add a user in india group
#adduser
a2 to add a new user
Set a1 and a2 user passwd
#
india data to change group
#chmod
775 /data to set
permission on data folder
(here 7=owner, 7=group,
5=other)
7=root, 7=groupmember a1 5=other a2
#ls
-ld data to check permission
Drwx rwx r-x
2 root root 4090
here
rwx=owner rwx=group r-x=other 2=no.of
content root=owner root=group 4090=size
owner
groupmember other
r =read 4 4 4
w=write 2 2 0
e=execute 1 1 1
4=read 2=write 1=execute
775 permission on data folder means
Owner=full groupmem.=full other=read+execute
Now login from a1&a2 user and run #cd
/data command.a1 user can save
file and directory but a2 user can not save file or directory.
#chown
username data to change owner of data folder(creat a user
setpasswd &run this command. Only root can change owner of file and folder.)
If we want to set special permission for a
perticular user in india group then run following command
#setfacl
-m u:username:rwx /data (here
m=manage, u=user)(permission will be
type ex: r-w )
#ls
-ld /data username
#getfacl
data
Above both r use to check permission
#setfacl
-x u:username:rwx file /folsder
name (to romeveacl)
#setfacl
-x g:groupname:rwx
file/folder (to set facl for
group)
#chmod 775 data –R to set permission for data subfolder also.
Special permission (sticky bit and SGID)
SGID =special Groups ID
Sticky bit protect file and folder from deleting
by members . and sgid set special group stamp on file created by different
group members. Setting sticky bit..
#chmod o+t data it
will assign t or T in place of in place of x
#chmod
o+s data it will assign s or S in place of in place of x
************
Changing permission – symbolic method:-
chmod command is use to change access modes
|
WHO MAY BE
|
OPERATER MAY BE
|
PERMISSION MAY BE
|
|
u=user who owns the file
|
+ add a permission
|
r=read
|
|
g=user’s in the file groups
|
-
Remove
permission
|
w=write
|
|
O=other users
|
= assign a permission
|
X=execute or cd
|
|
a=all three categaries
|
|
S =set user id bir or group
|
|
|
|
T=sticky bit (for directory)
|
Ex:
#chmod ugo+r filename (grant read access to all for file)
#chmod o-wx directory
(deny write and execute to other for directory)
#chmod
u+w,go-w filename (grant write access to owner but denies it to group
and other)
#chmod
--reference file1 file2 (get the mode from file1 and place it on file2)
VNC
:-
used to manage computer remote location by
graphical prompt.
It is virtual network computer.
#yum install rdesktop*
#yum install vnc*
Configuration open graphical mode.(init 5)
Login by root then
System→preferences→remote desktop→
al
low other users to view your desktop→
allow other user to control your desktop
|
\
|
Client end
#yum install vnc*
(open graphical mode .login by root )
Application→accessories→vnc viewer→ip
&passwd.
Troubleshouting:-
#runlevel (to
check our runlevel)
#vim
/etc/inittab
Id:5:initdefaullt (if we
want to change our default run level then we can 1,2,3,4, in place of 5.
In this file in below there are avalable. Here we can increase or decrease
terminal no.but we can extend only 11 command prompt terminal and 1 graphcal terminal
. because there are only 12 function key are available on keybaord.)
If
our system is in command mode and we want to come in graphical then type
#startx or
#X or
#init 5
If we create a partition and mount it then
we have to entry in fstab file.suppose we creat a new parttion named
/dev/sda5 mount it in /mnt folder but it
is temparary mount to mont permanantly we have to entry in fstab file
#fdisk /dev/sda
N
Entr only
+500M
W
Reboot ur pc or run partprobe
#mkfs.ext3
/dev/sda5
#mount
/dev/sda5 /mnt
#df
-h to check
mounted partition
But it is temporary mount to mount
permanantly entry in fstab file.
#vim
/etc/fstab
/dev/sda5 /mnt ext3 defaults 0
0
:wq!
#mount
In this file if type 1 2 or 1 1 in place
of 0 0 then if we reboot our system then system will not boot and ctrl d error
will display.or if there is entry of any partition but you have delete it by
fdisk command then ctrl d error also appear.
To solve this problem:-
Type root passwd→(now computer will be in
repair file system mode here if u want to change in
#vim /etc/fstab file changes will not save
becase here permission is only read only.now we have to run remount and read
write permission command. )
#mount
-o remunt,rw /
And now run
#vim /etc/fstab (now delete that line in which u have entry 1 1 or
1 2 or delete partotin but line is exist.). ifu dont want to remove ur partiton
then create a partition.
SOME CONFIGURATION IN FILES:-
Note:- To take effect all these file u
have to logout and login again
#vim
/etc/issue to
set prelogin massage
#vim /etc/motd to set after login massage
#vim /etc/DIR_COLORS to change default files and foldre
colors.
1 #vim
/etc/grub.conf OR
2 #vim /boot/grub/grub.conf
Above 1 2 command’s files are title files.
These files are use to change booting o/s if ur pc is loaded from two o/s
defaults time out and mimu option.
#vim /etc/inittab to change default runlevel an and use to extend terminal
(here change only initdefaults no.)
To extend virtual terminal no.
1:2345:respawn:/sbin/mingetty tty1
(copy above line and paste at end and
change serial no.)
#vim /etc/profile to change history size
(don’t make changes in this file except
HISTSIZE )
The command history will be in
#vim /root/.bash_history
#vim /etc/bashrc to start any programe automatically when user login on the
sytem(startup file)
To set any progrma:- open above file and come in insert mode
mkdir
/irfan
:wq!
Logout and login again. It will creat /irfan
folder automatically.
Alias :- to set shortname or shortcut for
any command
#alias c=clear
#alias h=history
When u will type c and press enter clear
command will berun. But it is temperary.to set permanant open
#vim /etc/bashrc
alias
c=clear
:wq!
Then logout and login again.alias has set
permanant.
#alias
to check
alias
#unalias c to remove alias
RPM {redhat package manager}
Insert linux dvd in dvd drive
#dmesg | grep “CD” to know about cd/dvd
#mount /dev/sdc /media To mount dvd(sdc is ur dvd controller)
#cd
/media to come in dvd
mount folder
#cd
Server to come in Server folder
#rpm
-ivh packagename to
install package
(i=install
v=verbose h=print the hash% bar
progress bar)
#rpm
-qa packagname to query about package (q=query a =all package list)
#rpm
-e packagname to erase
package (-e=erase)
#umount /media (to unmount media because to eject ur dvd
first u have to unmout dvd)
#eject
OR #eject -t (to
eject ur dvd)
Shell scripts:- (file extension must be
.sh)
To create shell scripts
#vim
filename.sh
#vim
backup.sh
Come in insert mode
mkdir /irfan
cp
-rv /etc /irfan
:wq!
To run scripts
#sh filenme.sh
Swap
partition:- if we want to extend vurtual
memory we have to add a new partirtion and format by swap filesystem then
enable swapping.
Step:-1
Creat a normal partition.
Change the system id 82=linux swap
Save the partition and partprobe
Step:-2 to format part. By swap
#mkswap
-v1 partition no. (v1=
version one
Step:-3
enable swapping on partiton
Put entry in fstab
#vim
/etc/fstab (insert mode)
/dev/sda5 /swap swap default 0
0
:wq!
Then run following command
#swapon
partition no.
T o enable swaping in partition
#mount –a To
load new setting from /etc/fstab file
#swapon
-s to check
status
To remove swap partition:-
Remove entry from /etc/fstab
Then run following command
#swapoff
partion no.
QUOTA MANAGEMENT:-
To apply quota on the partition:-
That parttion must be mounted in userquota
mode
That partition must be user writable
To mount partition in userquota mode
#vim /etc/fstab
Linux provid two types of login screen
1
command 2
graphical
default graphcal environment called GNOME.
To switch from virtual consle to grapical console type ctrl+alt+f7
Changing ur paassswd:=
GUI:- system→preferences→about me and the click CHANGE PASSWD
CLI:- passwd
The root user:-a special adminnistrative
account.also called super user.
Root has all complete over the system.
#su -username (switch user)
#id username (to view user id)
Tab is very useful option in linux. U can use tab key to complete ur
commacd
Suppose u create a a file named myfile
#touch myfile
If u type
#ls myftab
It will open myfile.
Use the up and down keys to scroll through previous
Type ctrl+r to search for a
command in commadnd history
Nano is text file editor to creat a file
#nano filename
Nano is easiest editor t learn. It use ctrl key use it. Two line
display it’s menu.for ex: if u want to exit frome file press ctrl+x
#passwd username (this command is use to change user passwd.)
You can run seperate multipl e command on the same line with
semicolons.when the firtst command finishes the next will be execute. For ex:
#mkdir irfan; cp irfanfile irfan (it will creat a directory
irfan and will copy irfanfile in irfan directory.ensure that irfanfile created file.)
Geting help:- do not try to memorize everything.
Linux provide many level of help
1 man commandname
2
info commandname
3
command name -- help
(t o quit press q)
Whatis command name (short description of commad sometimes it is not
avalable after fresjh installation so u
have to creat it ot create whatis run this
command
# makewhatis )
In info command u can use following switches
n/p/u/1 goes to the /next/previous/up-one/last node
linux help guide available at follpwing path
system→documentation→deployment Guide.
Linux are case censative. Directory names may be up to 255
charactors.all charactors are valid except the forward slash.
#vim /var/named/reverse.zone
#service named restart
#nslookup server.jagdamba.com
# nslookup 172.16.172.16
#dig jagdamba.com
(for more detail)
#dig
–x 172.16.172.16
http_access allow ournetwork
(on line no.903 by default http port is
enable)
(on line no. 1576 set cache memory so
remove # & set of ram)
Cache_mem 256 MB
(on line no. 1783 enable cache directory
and size for storing web sites)
Cache_dir ufs /var/spool/squid 100 16 256
(On line no. 1945 access log is enable by
default)
(on line no. 4148 insert new line and set
dns server address)
dns_nameserver 202.56.224.153
(save and exit) restart squid
Client
end
At client end oper internet browser and
enable connection via proxy.
In internet explorer
Tools>internet options>
connections> lan settings>proxy configuration.
(define proxy server ip address and port
no. 3128)
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