LINUX NOTES
NFS
Packages:
1. nfs
2. portmap
Config file :
/etc/exports
[ Open the file
add the location which you want to share in network ]
example :
/media/floppy 10.0.0.1/(rw)
– To share with secefic machine
/media/cdrom 10.0.0.0/255.0.0.0/(rw) - To share with 10. network
/var *
(rw) - To share with all
the network
Activate service
# service
portmap restart
# service
nfs restart
Not clear with command
# exports
–r
Client side configuration
# mount –t
nfs 10.0.0.1:/root/viswa
/mnt/nfsmountpoint – server IP
and location
To view shared file in server
# exportfs
To view shared file in client
# showmount –e (server IP>
Note : for the permanent mounting :
Open
/etc/fstab file and make entry in that
To activate service on booting time
# chkconfig
portmap on
# chkconfig
nfs on
Note IP assign
#
system-config-network
# netconfig
User quota
Each file will occupy 4 blocks one block is 8 M.B.
It is advisable to create separate partition for all the home
directories
Config file :
/etc/fstab-
along wih default add [ Default,usrquota,grpquota ]
Remount
# mount –o
remount,rw /home
To create quota file
#
quotacheck /home
# quotaon
–a – To set the quota to all the user
# quotaoff – a – no idea
Setting quota for users
# edquota –u <user name>
Note :
Ls –i – check inode of a file
One file
will occupy 4 blocks
All the
admin command stored in /sbin
Crontab schedule
To create
automatic task
Date and time settings
# date
030215552008(MMDDHRMINYEAR)
Creating auto scheduling
# crontab
–u root –e – After command given it will open a editor inside that we have to
type
05 16 02 03 07 /sbin/init 0 (min hr day month dayofweek file
to be executed)
05 15 02 03 07 tar –cvf <destination> <Source>
:wq
Service to be restarted
Service crond restart
To list particular user schedule
# crontab
–u <user name> - L
Backup & restore
Restore
from backup files :
#
tar –xvf /root/backup/doc.tar
Backup
files
# tar
<destination> <Source>
# tar –cvf /root/file name
/usr/file name
# tar –cvf /dev/fd0 /root/file – to
backup in floppy
Read backup files
# tar –tvf <file name>
DHCP
Packages:
1. dhcp
Config file:
# cp /usr/share/doc/dhcp-3.0.5/dhcpd.conf.sample
/etc/dhcpd.conf
Open dhcpd.conf file goto line
number 5 and type following things
Subnet 172.24.0.0 netmask
255.255.0.0
{range 172.24.0.2 172.24.0.50;};
:wq
Service to be restarted
# Service dhcpd restart
MAC based IP assign
Goto
the last line of dhcpd.conf file and type the following
Host <host name>
{
{
hardware 00:01:1B:B9:92:02
fixed address
172.24.0.15;
};
Dhcp client configuration
#
rpm –ev dhcp* - no idea
#
rpm –qa dhcp * - To search the installed package
#
rpm –qa | grep dhcp*
·
Only RPM installation is mentioned as per my
notes
FTP server
Packages
1. vsftpd(Very
secured file transfer protocol)
Config file:
#
vi /etc/vsftpd/vsftpd.conf
Service to be restarted
#
service vsftpd restart
User name for FTP access
User
: ftp
Password
: anypassword
FTP users home directory
/var/ftp/pub
Client side configuration
#
ftp <Server ip>
Enter
the user name & password
Ftp user file
·
files are who restricted to transfer file in FTP
will be located in below given files
1. /etc/vsftpd/ftpusers
2. /etc/vsftpd/user_list
Download and upload file from
FTP
#
get <file name>
#
put <file name>
# mget <filename > - for multiple
file
#
mput <filename>
Changing computer name
1. /etc/sysconfig/network
2. /etc/hosts
3. #
hostname <new name>
DNS
Packages
1. bind
2. catching
name server
Config file
/var/named/chroot/etc/named.rfc1912.zone
(IN EL 5)- Go to the line 37
Forward lookup
Zone “visu.com “ IN
{
Type master;
File “<visu.zone>”;
};
Reverse lookup
Zone “0.24.172.in-addr.arpa” IN {
Type
master;
File
“<filename.local>”;
Allow.update
{ none;};
};
Creating .zone and .local
/var/named/chroot/var/named/visu.zone
/var/named/chroot/var/named/visu.local
Inside .zone file
IN
SOA visu.com root ( note:Remoove
the @ symbol
42 ---
---
IN NS station1.visu.com
Visu.com IN A
172.24.0.254 # for web server (Remove the @ symbol)
---
:wq
Change group
Chgrp named <filename.zone>
Chgrp named <filename.local>
Named.conf file
# cp named.catching-nameserver.conf named.conf
# vi named.conf
Goto line
number 16 and comment it
In line number 17 type
listen-on port 53
{172.24.0.0/16;};
In line 26
Allow-query
{172.24.0.0/16;);
Goto line 36 and 38 type
Match-clients
{localhost;};
Match-destination{172.24.0.0/16;};
Resolve.conf file
Open
/etc/resolve.conf file and type
Name
server <DNS server IP>
In /etc/hosts file
<IP> visu.zone station1.visu.com
Service to be restarted
# service named restart
To check the DNS
# dig
station1.visu.com
Note : kudzu – For plug and play linux hardware config tool
Web server configuration
It has to
be done where webserver configured
Packges
1. http
Config file
# vi /etc/httpd/conf/conf/httpd.conf – Goto
last line <use ‘Esc and G for last line >
<virtual
hosts <zonename> visu.com:80>
Document
root /var/www/html
Servername
visu.com
</virtual
host>
:wq
Create HTML file
# vi
/var/www/html/index.html
Service to be restarted
# service
httpd restart
To open the webserver
#elinks
<webserver name>
Virtual hosting
One machine
contain more than one webserver is called virtual hosting
.Zone file
Type
followings
www1.example.com IN A
[172.24.0.1]
www2.example.com IN A [172.24.0.1]
httpd.conf
In the
beginning of the file type original webserver name
At the end
of the file type virtualHost www2.example.com
For centralized user
management
Packages
1. ypserv
2. yptools
3. ypbind
Service to be restarted
# service ypserv restart
To set the NIS
# nisdomainname <Name>
Config file
# vi /etc/sysconfig/network and type the following
NISDomain = RHCE
:wq
Create NIS
# useradd –d /server/mnt/singh –m singh
# passwd singh
# service ypserv restart
Home directory sharing
# vi
/etc/exports and type the following
/home
<Machine IP> (rw,sync)
:wq
# service portmap restart
# service nfs restart
Create NIS
# /usr/lib/yp/ypinit –m
# service yppasswd restart
- Ping the server
- Setup
– Authenticate conf –
- Give the domain name and IP
- Service ypbind restart
- check the dmain name using “nisdomain” command
Config file
# vi /etc/auto.master goto last line and type
/rhome/etc/auto.misc
#vi /etc/auto.misc and type the
following at the end of line
User name permission Home directory location
Singh rw,soft,intr 172.24.0.254:/home/singh
:wq
#service autofs restart
Note: To empty log files # >
<file name>
Note : To shutdown after 5 minutes
#shutdown –r+5 –to
Note : Mahine IP will stored in
following files
/etc/sysconfig/network-scripts/ifcfg-eth0
– In this file change the onboot option as yes
Note : To bring
down NIC card (Still loop back will run)
# ifconfig eth0 down
# ifconfig eth0:1 down
Virtual IP
Assigning
more than one IP in a NIC is called virtual IP
# ifconfig
eth0:1 10.0.0.3
# ifconfig
eth0:2 192.138.10.1
Partition
View
# fdisk –l
Label name view
# e2 label /dev/sda1
# e2label /dev/sda2
Note : Mount points are different
from label
Permanent mount point
# vi /etc/fstab
Remount the specific partition
# mount –o remount,rw /dev/sda
Tourbleshooting
Run level problem
# vi /etc/inittab(Like only graphic mode or
command mode ) – Go to line number 18
While booting press ‘G’ + give
Space ‘S’ => Single user mode
Init 2 – Multi user mode with NFS
Init 3 – Multi user mode with NFS
Init 4 – Usual
Init 7 – Graphic
Init 6 – Reeboot
Greb file troubleshooting
# vi /etc/greb.conf – There is a
option like default & timeout
Default – To change default boot
O.S.
Timeout – To change the seconds
before boot
Note : To view the kernel version
use following command
# uname –r
Note : To turn off the send mail
option
#chkconfig sendmail off
IF Grub.conf file is corrupted
- Boot from 1st CD
- Type “linus resuce”
- Type chroot /mnt/sysimage (Linux restore the rescue image in /mnt/sysimage)
- vi /etc/greb.conf
- Do the necessary changes and save and reboot
IF fstab file corrupted
IF the fstab file is corrupted system will not
boot boot same as above given and do the necessary changed in fstab file
# mount –o remount,rw <mount
point>
If inittab file corrupted or option changed
#
vi /etc/inittab will show all the init option in the linux if the meaning of
init is changed in that file linux wont boot properly.So when you set boot menu
è
Press ‘A’ space type ‘s’ – to boot the system in
single user mode and do the necessary changes in initab file
User login problem
If
the user prompt (-s) given improperly then that user unable to login use
# chmod –s /bin/bash
<username> - to fix the problem
To lock & unlock the user
#passwd
–l <user name> - To lock the user
#
passwd –u <user name> - To unlock the user
Shadow file corruption
If
the shadow file is deleted that user
will not able to login. Shadow file contain user information.
# vi /etc/shadow – To view the
shadow file
Problem in fstab & grub file
- Boot using linux 1st CD
- Type linus rescue while booting
- fdisk –l
- #e2 label /dev/sda1 – If the output is boot then it is the boot partition next partition will be /root partition
To mount the root partition
- mkdir /nita
- mount /dev/sda3 /nita
- cd nita – after these steps sysfile will be automatically created inside nita
- #cd etc – Now grub.conf file will not available so first correct vi /nita/etc/fstab
- # init 6 – Again boot from CD
- type chroot /mnt/sys/mas2
- Now the chroot option in root window is available so we can fix the problem by doing necessary changes in grub.conf file
- Final step is –boot is single user mode
change the root password
LVM
Is an extendable partition usually
it is a good practice to configure /home directory as a LVM
To set the LVM partition
- PV
- VG
- LVM
To convert LVM partition
- Create usual partition
- Type option ‘t’ in fdisk –l
- 10 – is the partition name
- 8e – is exacode for LVM
Physical volume (PV) creation
# pvcreate <lv partition
name> - to create PV
# pvcreate /dev/hda10 /dev/hda11
Increatse the PV size
# pvcreate /dev/hda12 – to add
space with existing partition
Volume group
# vgcreate <vgname> - to
create vg
# vgextend <vgname>– To
extend the vg
# vgcreate <any new vg name>
<disk>
# vgcreate /dev/hda11 /dev/hda12
LVM creation
# lvcreate –l or –L+1024 –n
<LV1(new LV
# mkfs –t ext3 /dev/vg1 /lv1
# mount <LVM> <Mount point>
To increase LVM
Lvextend – L+1024m –n /dev/lvm/vg1
To findout the names
# pvdisplay – To find PV name
# lvdisplay – To find LV
# vgdisplay – to find VG name
To remove LVM
- lvremove <device name>
- vgremove <device name>
- pvremove <device name>
Installation
- Boot with CD
- type “linux askmethod” – for various option (like nfs or remote installation)
- nfs servername / IP
- package path /var/ftp/pub
RAID
Minimum 2 hard disk
is needed of the same size.Device should looks like
For raid – md0
For floppy – fd0
For Hard disk – had or sda
RAID manage command
# mdadm
Creating RAID partition
1. Create
same size partition or add 2 same size hard disk
2. fdisk
/dev/had and type t fd /dev/hda (fd is
hexa code for raid)
3. Create
a file system for new partition or hard disk
# mkfs t ext3 /dev/sda3
# mkfs t ext3 /dev/sdb3
4. #
mdadm – - create /dev/md0 – - level=5 – - raid-devices=2 /dev/sda3 /dev/sdb3 –
To create Raid
5. #
mkfs –t ext3 /dev/md0
6. #
mount /dev/md0 /home
7. Create
permanent mount
# vi /etc/fstab – inside file
/dev/md0
/home ext3 defaults 0 0
To view the Raid
details
# mdadm – -
details /dev/md0
Replacing hard disk
# mdadm --
manage /dev/md0 – - add </dev/new hard disk or partition>
Remote login
# ssh <IP>
# rsh <IP>
Swap Post installation
If we upgrade system & we want to add more space in swap
- Create new partition
- change its hexa code to 82 using ‘t’ in fdisk /dev/hda
- To change new partition to swap file system
# mkswap /dev/sda7
- Activate swap partition
# swap /dev/sda7
- Make permanent mount in fstab
# vi /etc/fstab and type following
---- /dev/sda7 swap swap default 0 0
:wq
To see the swap details
# free –m
# cpuinfo – To see
mother board information.
# vi /proc/cpuinfo –
To see mother board information.
Samba server
Used to
share resource between window and linux
Package
- samba
Config files
1. /etc/samba/smb.conf
– inside this file
Change worgroup=<name of using
wrk group>
Change host allow = <client IP
or Nerwork IP>(eg. 172.24.0.0/255.255.0.0)
Change sharing location
[share
name]
Path
= /home
Browsable
= yes
Read
only = yes
Writeable = yes
Valid.users
= <user name> / public =yes
Service to be restarted
# Service
smb restart
To view the shared files
# test parm
Mailserver
1. For
incoming – we use dovcot
2. For
outgoing – We use sendmail
Packages
1. dovcot
2. sendmail
Incomming mails
# vi /etc/dovecot.conf – Goto line number 17
and type
Protocols =imap
imaps pop3 pop3s
Imaps – Internet message protocol security
Outgoing mails
# vi /etc/mail/sendmail.mc (.mc – means macro file) – Goto
line number 116 & type
Dnl # daemon-options(‘port=smtp;addr=127.0.0.1;name=MTA’)dnl
# m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
Note: dnl – keyword used in macro file to disable the lines
Mta – mail
transfer asent
.cf – is an
configuration files.All the macro file changes stored in .cf files
Service to be activated
# service dovecot restart
# service sendmail restart
Mail ID
All the mail id will
be looks like username@webserver.com
(test1@example.com)
Sending mails
# mail test@webserver.com <enter>
Sunbject :
<Enter any subject>
---------------------
---------------
Press dot and enter
to finish and send mail.
# mail test@webserver.com /test.txt <enter>
- to send mail with attachment
Read mail
After logged in just
type mail and give the number of mail which you want to read
Come out of mail
To come out of mail
just type ‘quit’
Note: All user mails will be stored in
/var/spool/mail/<user name>
Once mail
red it moved to mbox
# vi mbox – to see mbox (mbox stored in users home directory
Forwarding mails
# vi /etc/aliases – From this location we can forward mails
Eg: venu: root,venu
ACL
Access control list – To set the permission for the
particular user
ACL for specific user
# set facl –m u:singh:rwx /root/<file name>
# getfacl <file name>
To remove permission
# setfacl –x u:singh /root/<file name>
Sticky bit
# chmod 7777 <file name> - The last 7 is called sticky
bit it protect the file from users . They cant delete it
Umask
Defauls usmask will be – 0022
Folder mask permission is – 777(Default folder 777-022 =
755)
File mask permission is – 666 (Default folder 666-022 = 644)
Change the umask value
# umask 222
Note : File and folder permission value set based on umask
value
Creating hidden files
# cat > .nita
– To create hidden file
# ls –a – To list all the file including hidden files
# cat .nita – To read file
# mkdir .<foldername>
- To creatd hidden folder
Firewall
To protect the network from unauthorized network
Config firewall
# iptables – L – To see the firewall status
# iptables – F – To delete rules
Block a PC FTP access
# iptables – A INPUT –P tcp
# iptables – A INOUT –P tcp – -dport 21 –S
172.24.0.0/255.255.0.0 –D 172.24.0.254 – -J DROP
a- add
p- protocol
dport – destination port
s- source
d- destination
j – To apply policy
#iptables –D INPUT 1 – to delete particular rule
Allowing particular network to use FTP
# iptables – A INPUT –P tcp – - dport 21 –S !
172.24.0.0/255.255.0.0 –d 172.24.0.254 - - J DROP – IF the source is not
mentioned it will take as anonymous
# iptables –D INPUT 3
# iptables save
Note :All port details stored in /etc/services file
TCP Rapers
Config file
1. vi
/etc/hosts.deny
2. vi
/etc/hosts.allow
è
If we put the entry in .deny file it means Drop
è
If we put the entry in .allow file it means
Allow
# vi /etc/hosts.deny
Goto last line and type
Vsftpd:172.24.0.0/255.255.0.0
Note : In TCP rappers first preference given to allow file
Remote installation
- Boot with linux 1st cd
- type linux askmethod
- Select installation method NFS image
- Enable ipv4
- In NFS server IP address area give the IP
- remaining steps as usual
SSH(Secured shell )
Package
- Openssh
Service to be restarted
# service
sshd restart
# service
shd status
Telnet
Packages
1. xinet
2. telnet
Config file
# vi
/etc/xinetd.d/telnet- In that file change the last line “disable=no”
# service xinet
restart
Rlogin
Packages
- rsh
- xinet
Config file
# vi
/etc/xinet.d/rlogin – Change the last line (i.e. disable=no)
Service to be restarted
# service
xinetd restart
Client side configuration
# rlogin
serverip –L <username> - To login from remote
Xwindow
Is
graphical window
Packages
# xorg * -
More than 200 packages exists
Config file
# vi /etc/x11/xorg.conf –
Service to be
retstarted
# Service xfs restart
Note : To create xorg file use “system-config-display”
Kernal
Kernel version information
stored in file /etc/grub.conf
/proc – is the kernel directory
Upgrade kernel
# rpm –uvh
xen-libs-3.0.3-25.el5.i386.rpm
Squid configuration
Package
Squid
Config file
# vi
/etc/squid/squid.conf –Set the line number
In
line number 73 (http 3128) remove the comment ‘#’
In
line number 738 create a new line and type “cache-mem 64 MB
In
line number 993 (cache.dir…) remove the comment
In
line number 2243 (acl nita – - src 172.24.0.0/16) remove the comment
In
line number 2244
Eg1: http-access
allow/deny nita
Eg2: acl
linux1 src 10.0.0.1
http-access allow linux1
Eg3: http-access
deny all
In
line number 1353 give the DNS
Dns-nameserver 203.145.184.32
Note: squid default port number is 3128
Printer configuration
Types of printer concept
1. local
printer
2. linux
printer
3. window
printer
4. novell
printer
5. Jet
direct printer
# startx –
to start to linux graphical mode
#
system-config-printer – type the above command in graphical mode
Note : Network printer port is 9100
Taking printouts
# lpr
<file name>
Process management
# ps –ax –
to display all the running process
# ps –ax |
wc –l
# ps –ax |
grep tty – To see the process detail in terminal
# kill -9
<pricess id> - to kill the process (-9 is for immediate kill)
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