Transcript Everything is a file

Certificates
•
•
vendor certificate
vendor neutral
RedHat
Unix History
• Bell labs: Unix was originally developed for internal use at AT&T Thompson
and Dennis ritchie. AT&T licensed the source code, widely allowing many
companies to modify and produce UNIX-like operating system, Because
AT&T held the name UNIX name, other companies had to create their own
names to brand the modifications and addition they had made. AIX from
IBM,HP/UX from Hewlett-Packard, SunOS (later Solaris) from sun and IRIX
from SGI.
• UNIX Flavors: These many flavors of UNIX operate in a similar manner. At
shell prompt, most offer the same standard utilities and commands, although
the parameters a command uses may vary from system to system. One can
compare UNIX to cars. There are many different makes and models of cars,
but fundamentally they all work and are operated the same way, though
there are minor differences.
Unix principles
• Everything is a file (including hardware): Unix systems have many
powerful tools to manipulate files. The UNIX security model is based around
the security of files. By treating everything a file, you can secure access to
hardware in the same way as you secure access to a document.
• Configuration data stored in text: text is a universal interface, and many
UNIX utilities exist to manipulate text. Storing configuration in text allows an
admin to move a configuration from one machine to another easily.
• Small, single-purpose programs: Unix provides many small utilities that
perform one task very well. When new functionality is required, the general
philosophy is to create a separate program . Rather than to extend an
existing utility with new features.
• Avoid captive user interfaces: Interactive commands are rare in UNIX.
Most commands expect their options and arguments to be typed on the
command line when the command is launched. The command completes
normally, possibly producing output, or generate an error ,message and
quite. Interactive is reserved for programs where it makes where it makes
sense,
• Ability to chain programs together to perform complex tasks. A core
design feature of UNIX is that output of one program can be input for
another. This gives the user the flexibility to combine many small programs
together to perform a larger, more complex task
GNU project
•
•
•
•
•
•
GNU project started in 1984
Goal: create free UNIX clone
By 1990, nearly all required user space applications created
GCC, emacs etc
Free software foundation
Non-profit organization that manages the GNU project
Appin
Free software
• The term “Free software” may have different meaning than you expect. The
term doesn't refer to the cost of the software, but fact that end user has the
freedom to modify and change the program. The GNU web site reads , in
part:
• Free software is matter of liberty not price. To understand the concept, you
should think “free speech” not free “beer”
• Free software refers to the users, freedom to run, copy, distribute, study,
change and improve the software.
General Public licence
•
•
•
•
•
Primary license to open source software
Encourages free software
All enhancements and changes to GPL software must also be GPL
Often called copyright
All rights reserved
Linux
Open source licenses
• Most of the utilities and applications included with Redhat Linux are also
covered by the GPL. One major exception is the X windows system. Which
has its own terms and conditions. The text of the GPL can be found
http://www.gnu.org/copyleft/gpl.html
• A few applications have their own licensing agreement which must be
agreed before they can be used.
• All of the software contained in RedHat Linux is free for end user. However,
if you are going to be developing commercial application, read the
appropriate licenses and agreement first.
Linux Origins
•
•
•
•
Linus Torvalds
Finish college student in 1991
Created Linux kernel
When Linux kernel combined with GNU applications, complete free UNIXlike OS possible
• Linus Torvalds announced Linux in the comp.os.minix newsgroup in
august 1991.
Think Security Think Linux
Why linux
•
•
•
•
•
Fresh implementation of UNIX APPIs
Open source development model
Supports wide variety of hardware
Supports many networking protocols and configuration
Fully supported
The Best Operating system
• Linux is a UNIX-like OS: Linux is as similar to UNIX as the various versions
are to each other. Conceptually, anything that can be done with another
version of UNIX can be done with Linux operating system, although the
means may vary slightly
• Multi-user and multi-tasking: Linux is a multi-user and multi-tasking
operating system. That means more than one person can be logged on to
the same Linux computer at the same time. And a user can have more than
one process executing at the same time.
• Wide hardware support: RedHat Linux supports most pieces of modern
x86-compatible hardware. In the early days of Linux hardware support was
limited: today Linux support has become a check list for hardware vendors.
• Fully supported: Red Hat is fully supported distribution
Virus free
Recommended Hardware
•
•
•
•
•
Pentium pro or better with 256 MB ram
64-bit Intel/AMD with 512 MB ram
2-6 GB disk space
Bootable DVD
And kaaaali dunya
Recommended Hardware
Sources of Installations
•
•
•
CD/DVD ROM
Hard Disk
Network (NFS,FTP,HTTP)
Linux Installations
File system In Linux
File system Hierarchy
• / : This is the topmost directory in Linux directory structure.
• /boot: This folder contains the all important booting files which are required
to the Redhat machine including the boot loader software & the kernel of
Linux
• /etc : This folder contains all important system & configuration files.
• /home: This folder contains the home folder for the users . Where users
store their personal data.
• /root: This is the home folder for Linux administrator( root user)
• /usr: This folder contains all important programme files of the application
which we install in machine.
• /bin : All important binaries(cmd) which can be executed by the user.
• /sbin: All important binaries(cmd) which can be executed by any super user.
File system Hierarchy
• /opt : This folder contains the all important programme files of the
application , like third party software
• /var : This folder contains the all important variable files ( such as logs).
File system Hierarchy
Boot Loader
• Boot loader: It is a special software which loads the booting files (kernel)
from hard disk into computer memory so that computer can get started. In
Linux operating system GRUB Grand unified boot loader) and LILO is used.
• Mount point: Is a special point which can be used to access the partition in
a hard disk . e.g. C: D: or /data
Text Editor
• The vi or vim editor can be used to create edit a file in Linux operating
system. And it has three modes.
• 1) cmd mode : File editing commands like copy, paste, search, replace,
delete
• 2)Insert mode: It can be used to insert text or delete text in a file.
• 3)ex mode : Exit mode is used to save the text in a file and can be used to
quit from a file.
•
vi abc
( can create a file)
Press I
( to insert text in a file)
Press esc (to come back to cmd mode)
Press esc (to ex mode)
Press :w
(to save text in a file)
Press :q
(to quit from a file)
Press :wq (to save & quit from a file)
Text Editor
Press :q!
to forcefully quit without saving
Press :wq!
To forcefully quit & save a file
Press :u
to undo last changes
Press :abc
(to search abc from a file)
Press yy
to copy a line
Press p
to paste
Press dd
to delete a line
Press 5 dd
to delete 5 lines
Press 5yy
to copy 5 lines
Press ctrl + r to redo
Press o
to insert a line down
Press shift + o to insert a line at up
Press shift + g to insert a cursor at end of the last line
Text Editor
•
•
•
•
•
•
Press shift + m to put cursor in middle of screen
Press shift+h
to put cursor top of the screen
Press yw
to copy a word
Press yc
to copy a character
Press dw
to delete a particular word
Press 5+ dw
to delete no of words
cat > abc (create a file ctlr+d to save)
cat abc (displays the contents of a file)
cp /abc /root/abc (copy a file)
mv abc appin (rename a command)
mv appin /root (can move a file)
cat >> abc (append to a file)
File And directories
•
•
•
•
•
•
•
•
•
•
rm abc (can remove a file)
mkdir abc (create a directory)
rmdir abc (remove an empty directory)
rm –r abc (delete directory recursively)
mkdir /data (create a directory)
mkdir /data/abc (create sub directory)
pwd (print working directory)
cd /data ( change the directory)
cd (change to home directory)
cd / (change to / directory)
File And directories
•
•
•
•
•
•
•
•
•
•
cd .. (come back one directory)
cd – ( back to previous directory)
tree /root ( to display directory structure)
rm –rf abc ( to delete a directory forcefully & recursively)
ls (list of files and folders in current directory)
ls –l (long listing of files & folders)
ls –a (list all with hidden files & folders)
ls / (list files & folders )
ls /abc/xyz (will list subdirectories)
cp –rvf /abc/xyz (copy recursively)
•
•
•
•
•
•
•
•
•
•
•
File And directories
ls *.txt (list .txt files)
history (displays last inserted commands)
!10 (run number 10th command)
!cal (run last command started with cal)
history –c (Clear all history)
man/info date (manual files)
makewhatis (creates what is database)
whatis cal (displays use of cal command)
cal > abc ( send output of cal to file abc)
date >> abc (append to abc file)
more sales.txt (displays page contents page wise)
File And directories
•
•
•
•
•
•
history | more (displays history page wise)
history | less (------------ can up and down)
history | tail -20 ( displays last 20 inserted lines)
History > history.txt (send history to a file)
tr ‘a-d ‘ ‘A-D’ < sam.txt ( display small to capital)
tr ‘A-D ‘a-d’ < sam.txt (displays capital to small)
Date and time
•
•
•
•
date (show system date)
cal 9 1751( show calendar)
date mmddhhmmssyy ( set date & time)
date 12051145302008
Find
•
•
•
•
•
•
•
•
find / -name sam.txt (find a file)
find / -iname sam.txt (search with capital & small)
find / -size 1 mb (find files with 1 mb size)
find / -size +1mb (find files > then 1 mb)
find / -size -1 mb (find files <then 1 mb)
find / -usr marc (find user marc,s files )
find / home –user marc (find user march in home )
stat /data/sam.txt (displays file properties)
Find
•
•
•
•
•
•
•
•
•
•
touch /data/sam.txt (update the time)
touch logitech
find / -atime +10
find / - atime -10
find / -mtime +10
find / -mtime -10
find / -name india.txt –not –user ashaq
find / -name kashmir.txt –not user root
find / -name india.txt –not –size -10mb
find / -name india.txt –and –user ashaq –not –size +10mb
User management
• updatedb (update locate database)
• locate sam.txt (search sam.txt file)
• User Account: User account used to manage security in our computer to
stop unauthorized access.
• Normal user: users who have limited access to system
• System user: System user special users with all rights .
• # useradd ashaq (add a user)
• # passwd ashaq (set password to user)
User managemnt
•
•
•
•
•
•
/etc/passwd (stores user database)
/etc/shadow (file stores the user passwords )
/etc/group (stores all groups)
# userdel ashaq (delete a user)
# userdel –r ashaq (delete a user with home directory)
# useradd –d /users/ashaq ashaq ( add user with home directory other then
default)
• # useradd –c “Amit kumar” amit (add user with additional info)
User management
•
•
•
•
•
•
•
•
Parameters in /etc/passwd file are .
chintu : a username
X: means encrypted password.
502: a unique user ID.
502: a group ID.
Chintu delhi : users details
/home/chintu :users home directory
/bin/bash : a login shell
Group Management
• groupadd sales
• usermod –g sales ashaq (primary group)
• usermod –G abc ashaq (secondary group)
•
A user can have only one primary
group and more then one
secondary groups.
• mkdir /data (make a directory)
• stat /data (check a user and group)
• groups ashaq (check primary & secondary groups)
• chgrp sales data (change group of directory)
User Management
•
•
•
•
•
•
•
•
•
•
usermod –s /bin/bash ashaq
usermod –s /sbin/nologin
usermod –u ashaq
usermod -l ashaq
chage –E never ashaq
groupdel sales (to delete a group)
/etc/shadow parameters
ashaq :login name
Xnvvgbbbf : encrypted password
115 : days before the password was changed
User Management
•
•
•
•
•
0: days after the password u can changed.
99999 :days after the password must be changed.
7 : expiry of password
0: password validity after expiry
12134 : days on which the account is disabled.
Permissions
•
•
•
•
•
•
•
•
Two type of method to apply permissions.
1) symbolic method
2) Numeric method
R= read, w=write, x=execute, - =noperm
4=read, 2=write, 1=execute, 0=noperm
Operation
+ = add, - = remove, = = overwrite
chmod can be used to change the permission. when a user creates a file or
a folder the user becomes owner of that file/folder. Also a group with a group
is created automatically by system.
• chmod u+rw,g+r,o+x /data
or
• chmod 641 /data
• stat /data
•
Umask
• A umask value plays an important role in file or folder permissions. The
umask value for root user is 022 and other users 002. we can change the
default umask value .
• The maximum permission on a folder created by root can be 777 but the
umask value gets less from actual permissions .
• 777-022=755 (default permission on folder)
• 666-022=644 (default permission on file)
umask
• The default vale on folder can be 777 which is created by user but the
umask mask value gets less from actual value .
• 777-002=774 (default folder permission)
• 666-002=664 (default file permission)
• umask (can be used to check the current umask value)
• # umask 044 ( can be used to set umask value)
Special Permissions
• SUID (Set use ID): Command will run with permission of the owner of the
command, not executor of the command.
• # chmod 4665 /etc/abc
• SGID(set Group ID):Command run with group affliation of the group of the
command.
• # chmod 2665 /etc/abc
• Sticky Bit : This is special permission for directories . The sticky bit on the
directory sets a special restriction on deletion of files . Only the owner of the
file and super user can delete files in that folder.
• # chmod 1777 /data
Access Control list
• Files and directories have permission sets for the owner of the file, the group
associated with the file, and other users in the system.
• However, these permissions sets have limitations. for example, different
permissions cannot be configured for different users. Thus ACL were
implemented.
• ACL- mounting file system: before using ACL for a file or directory the
partition for the file or directory must be mounted with ACL support. If it is a
local ext3 file system, it can be mounted by following command:
• # mount –t ext3 -0 ACL /dev/sda8 /data or
• Alternative: if the partition is listed in the /etc/fstab file, the entry for the same
is ;
• # vi /etc/fstab
• #/dev/sda8 /data ext3 acl 12 :wq*1090000909
ACL Types
• There are two types of ACL
•
1) Access acl : It is the access control list for
a specified files and
directories.
•
2) Default acl : It can be associated with a directory if a file with the
directory does not have an access ACL. It uses the rules of the default acl
for the directory. Default ACL are optional .ACL can be configured
• Per user
• Per group
• Via the effective right mask
• For users not into the user group for the file
Applying ACL
•
•
•
•
•
•
•
•
The setfacl command is used to set ACL for files and directories. use the
option to add or modify the ACL of a file or directory.
> setfacl –m _:_:_ filename (to set acl)
u =for users :username:rwx
g =for group :groupname:rw
o =for others : rx
# setfacl –m u:ashaq:rwx /etc/appin.txt
# setfacl –x u:ashaq /etc/appin.txt ( to remove applied acl on file)
# getfacl /etc/appin.txt ( to check)
Login Shells
•
•
•
•
•
•
•
•
•
•
Login shells are first shells started when a user login in to computer
Shells launched from a login shells typically are not login shells
Startup scripts: order of execution
1) /etc/profile ( used for all users logins)
2) /etc/profile.d (It provides the desktop environment)
3) /home/ashaq/.bash_profile ( for single user)
4) /home/ashaq/.bashrc ( for single user)
5) /etc/bashrc ( for all users)
No login shells
> ~/.bashrc /etc/bashrc /etc/profile.d
Bash scripts
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
vi /etc/profile
echo “Hello `whoami`”
echo “today is `date`”
alias cls=`clear`
vi /etc/bashrc
Set umask
vi /home/appin/.bashlogout
echo “Thanks for using system”
echo “system was running ‘uptime’”
echo “wait ……Your data is being processed”
for n in {10..1}; do
echo $n
echo “please wait”
sleep 1
clear
done
Some Important commands
•
•
•
•
•
•
•
•
•
grep appin /etc/passwd
ln –s /data /root/Desktop (Softlink)
ln /data /root/desktop (hard link)
cp , scp, ssh,
du –sh /data (to size)
df –h (hard disk)
wc sales.txt wc –w, wc –l, wc –c
wget, elinks, cross overoffice,
dd if=/dev/cdrw of=/win.iso
How to create partition
•
•
•
•
•
•
•
•
•
fdisk –l
fdisk /dev/…..
p (to list current partitions)
N ( to create new partition)
1000M ( to assign size of partition)
wq (to save & exit)
partprobe ( to update partition table)
mkfs.ext3 /dev/…
Mount /dev/… /mnt ( define mount point)
Delete a partition
•
•
•
•
•
•
fdisk /dev/….
d (to delete a partition)
Enter partition number
wq ( to save & exit)
partprobe ( to update table)
Remove fstab entry from /etc/fstab
Backups
•
•
•
•
•
•
•
•
•
tar –cvf abc.tar a b c d
tar –cvf abc.tar * (all files)
tar czvf abc.tar a b c d ( compress)
tar czvf abc.tar *
(compressed)
tar xvf abc.tar (to extract files)
tar –cvf abc.tar a bc d
bzip2 abc.tar or gzip abc.tar (compress)
bunzip abc.tar.gz gunzip abc.tar.gz (decompress)
du -sh abc.tar.gz
Basic Commands
•
•
•
•
•
•
•
•
•
head sales.txt (will display top 10 lines)
head –n 13 sales.txt (will display 13 lines)
tail sales.txt (will show last 10 lines)
tail –n 13 sales.txt (will show last 13 lines)
wc sales.txt (count words lines characters)
wc –w sales.txt (will count words)
wc –l sales.txt (will count lines)
wc –c sales.txt (will count characters)
grep ashaq /etc/shadow (search ashaq from file /etc/shadow)
Network configurations
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Sed ‘s/india/indians/’ english.txt
Sed ‘s/india/indians/g’ english.txt
# ifconfig (to check ip address)
# neat –tui (to assign new ip)
# service network restart
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
# vi /etc/sysconfig/network (hostname file)
# cd /etc/sysconfig/network-scripts
# cp ifcfg-eth0 ifcfg-eth:02
# vi ifcfg-eth0:02
# device =etho:02
# enter new ip :wq
# vi /etc/hosts
# 192.168.1.100 server.com
Network configurations
•
•
•
•
•
•
•
•
•
#Vi /etc/sysconfig/network-scripts/ifcfg-eth0-range
IPADDR_START=192.168.1.1
IPADDR_END=192.168.1.20
CLONENUM_START=0 :wq
# service network restart
# ifup/ifdown eth0 (enable or disable lan card)
# mii-tool –v
# /etc/resolve.conf (dns entry)
nameserver 192.168.1.1 :wq
Steps to create swap Partitions.
•
•
•
•
•
•
•
•
•
•
•
•
•
fdisk /dev/had
Com(m for help): n
Com(m for help):p
Com(m for help):1000M
Com(m for help):t (transfer partition ID)
Com(m for help):62 (for swap)
Com(m for help):wq
# partprobe (update partition table)
# mkswap /dev/..
# swapon –s (to check swap partitions)
# swapon –a ( to apply all swap memory)
# swapon /dev/hda7
/dev/hd.. swap swap 0 0 (in /etc/fstab file)
Remove partition & Grub Password
•
•
•
•
•
•
•
•
•
•
•
•
•
# swpoff /dev/hda
/etc/fstab (delete swap entry)
How to create Swap File
# dd if=/dev/zero of=/swapfile bs=1M count=1024
# mkfs /swapfile
# swapon /swapfile
Vi /etc/rc.d/rc.local
Swapon /swapfile
Enter Boot loader password
# grub-md5-crypt >> /boot/grub.conf (caution: don't use >)
# Enter password
# vi /etc/grub/grub.conf
password --md5 (paste passwd here) :wq
File Sharing
•
•
•
•
•
•
•
•
•
•
NFS (Network file sharing) can be used to share files and folders in Linux.
Install NFS
# mkdir /data
# vi /etc/exports
/data *(ro,sync) :wq
# service nfs start
# service portmap start
# chkconfig nfs/portmap on
# showmount –e <ip address>
# exportfs -v
Yum Server Configuration
• What is YUM: It is an automatic updater and package install/remove for rpm
systems. It automatically computes dependencies and figure out what things
should occur to install packages. It makes it easier to maintain groups of
machines having to manually update each one using rpm.
• Features:
• Multiple repositories
• Simple config file
• Fast operation
• Install vsftpd
• copy Linux DVD into /var/ftp/pub
• cd /var/ftp/pub
Yum server configuration
•
•
•
•
•
•
•
/pub# cp Server/repodata/comps-rhel5-server-core.xml Server
/pub# cp VT/repodata/comps-rhel5-vt.xml VT
/pub# cp Cluster/repodata/comps-rhel5-cluster.xml Cluster
/pub# cp ClusterStorage/repodata/comps-rhel5-cluster-st.xml ClusterStorage
Now Install createrepo package
/pub# rpm –ivh Server/createrepo…..rpm
/pub# createrepo –vg comps-rhel5-server-core.xml
/var/ftp/pub/Server
• /pub# createrepo –vg comps-rhel5-vt.xml /var/ftp/pub/VT
• /pub# createrepo –vg comps-rhel5-cluster.xml
/var/ftp/pub/Cluster
• /pub# createrepo –vg comps-rhel5-cluster-st.xml /var/ftp/pub/ClusterStorage
Yum server package config
•
•
•
•
•
•
•
•
•
•
vi /etc/yum.repos.d/abc.repo
[server]
name = my server
baseurl= file:///var/ftp/pub/Server
gpgcheck=0
[VT]
name = vt
baseurl= file:///var/ftp/pub/VT
gpgcheck
:wq
Yum Client configuration
•
•
•
•
•
•
•
Check connectivity by ping 192.168.1.100
Vi /etc/yum.repos.d/abc.repo
[Server]
Name=abc
Baseurl=ftp://192.168.1.100/pub/linux/Server
gpgcheck=0
:wq
Package management
• What is package?
• In the generic sense, an RAM package is a container of files. It includes the
group of files associated with a specific program or application, which
normally includes binary installation scripts, as well as configuration and
documentation files. It also includes instructions on how and where these
files should be installed and uninstalled.
• What is RAM?
• The RPM package manager greatly simplifies the distribution, installation,
up gradation and removal of software on RHEL system .
• Software to be installed using rpm is distributed through rpm package files
which are associated compressed archives information. Package files are
named using the following format . Name-version-release
architecture...rpm
Installing and removing software
•
•
•
•
•
•
•
•
•
•
•
•
rpm command is used for following functions.
Install
: -I
Upgrade : -u
Freshen : -f
Erase
:e
Example to run a command
# rpm –ivh vnc-2.3…rpm (to install package)
# rpm –e vnc (to remove)
# rpm –q (to queries any installed package)
# rpm –qa (to queries all installed package)
# rpm –qi (to show general information)
# rpm –qip (show general information of uninstalled
packages)
• # rpm – qlp (lists of packages of uninstalled packages)
• # rpm –ivh abc…rpm –nodeps ( install packages & ignore
dependencies)
CronD
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
It can be use to schedule reoccurring events
Use crontab to exit,install and view jobs schedule.
crontab –I list crontab jobs
crontab –r remove crontab
crontab –e edit jobs
Fileds in a crontab file can be separated by any number of tabs or spaces
crontab –e
*
*
*
*
* mkdir /data
Min
hour date month day of weak
(0-59) (0-23) (1-31) (1-12) (0-6) 0=Sunday
: wq
crontab –e ashaq (for a user)
Restrict /allow users to cron
/etc/cron.allow
/etc/cron.deny (define username to restrict)
/etc/crontab (the file is using to the set crond jobs for system)
Disk Management
•
•
•
•
•
•
•
•
System initialization: device recognition
Master Boot record (MBR) Contains:
Executable code to load operating system.
Space for partition table information, including
Partition ID or type
Starting cylinder for partition
Number of cylinders for partition
When s system boot, a search for code that can start an operating system is
made a list of devices as defined in the BIOS. The first executable code
found is used. Most often a system boot from hard drive attached to the
system main board, and from the code found at first sector, of the first
cylinder—the Master Boot record, or MBR—of the drive. This executable
code is called BOOT LOADER.
• There are many boot loaders which can be used an operating system. But a
boot loader do not load more than one OS at a time , even on multiple-boot
systems.
Primary partitions
• In addition to the boot loader described above, the MBR contains a structure
describing the hard drive partitions. IDE drives on Linux use legacy
structures to describe four primary partitions, with provision for an extended
partition and its “logical” partitions. Each partition, described by its size—in
sector, blocks or cylinders- and its offset from the “zeroth” cylinder, has a
type which is also stored in the MBR structure. Linux specific partitions
would normally be one of the following types.
• 0X5 Extended
• 0X82 Linux Swap
• 0x83 Linux
• 0x8e Linux LVM
• 0xfd Linux Raid.
• The total number of partitions supported by the kernel:
• 63 for IDE drives
• 15 for SCSI drives
Extended partitions and logical partitions
• If one of the primary partition is marked as Extended(type’0x5’) or wn95
Extended(‘0Xf). Then the first sector of the partition described by the entry
will contain another block of partition descriptions. These descriptions define
partitions known as logical partitions. Use of logical partitions is a workaround for limitations in the legacy.
• Why partitions?
• Unix best practices suggests that we should partition our disks for many
reasons. BY creating separate file system we can contain applications and
users to that file system. If it fills up because of security breach or user
demand, the rest of the operating system is more insulated from the issue.
Separate partitions improve performance by keeping data together which
reduces disk head seek. If you would like to use quotas, they are enabled at
the file system level. Also partitioning eases backup and recovery. If your
application and its data are on separate file system, the operating system
can be upgraded or reinstalled without having to restore the data from
elsewhere
Create a partition
•
•
•
•
•
•
•
•
•
•
•
fdisk –l (to check current partitions)
fdisk /dev/hd….. (refer to hard disk)
n (for new partition)
+1024M
(size of partition)
p (to check)
wq (to save and exit)
partprobe (to update partition table without reboot)
mkfs.ext3 /dev/… (format a partitions)
Mount /dev/… /mnt/data (define mountpoint)
Vi /etc/fstab
/dev/… /mnt/data ext3 (permanent) :wq
Logical Volume Manager
• A logical volume manager may be used to create virtual partitions called
logical volumes from one or more disk partitions or RAID devices. Each
partition, or physical volume, is assigned to a virtual disk called a volume
group. Multiple physical volumes may be assigned to the same volume
group, and a volume group may be partitioned into multiple logical volumes.
• Each volume group divides its pool of disk space into extents of identical
size. The size of an extent is set for a particular volume group when that
volume group is first created. An extent is typically between 1 MB and 64 MB
size . Extents may then be assigned to a new or existing logical volume in
the volume group currently, a single logical volume may contain at most
65534 extents, so larger extents allow larger logical volumes.
• The logical volume manager provides no redundancy by itself. If a single
physical volume fails, any logical volume which is assigned extents from that
volume will also fail.
• LVM provides flexible disk management. It is easier to resize logical volume
than it is resize normal disk partitions. New physical volume may be added
group, or existing logical volume can be reduced in size, providing additional
extents. Those extents can then be assigned to any logical volume in the
volume group. The file system on the logical volume being resized must also
support resizing. The standard ext3 file system currently supports off-line
resizing.
Logical Volume mnager
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Create partitions
fdisk –l (to list partitions)
fdisk /dev/.. (to create new partition)
n
(for new )
t ( to change partition type)
8e
(for lvm)
# pvcreate /dev/hda1 /dev/hda2 /dev/hda3
# vgcreate vg1 /dev/hda1 /dev/hda2 /dev/hda3
# vgchange –a y vg1 (activate vg)
# lvcreate –L 3000M –n lv1 vg1 (create lvm)
# mkfs.ext3 /dev/vg1/lv1
# mount /dev/vg1/lv1 /mnt/data (data should be existing)
# vi /etc/fstab
/dev/vg1/lv1 /mnt/data ext3 :wq (for permanent)
Logical Volume Manager
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Extend LVM size:
# umount /dev/vg1/lv1
# lvextend -L +200M /dev/vg1/lv1 (size will be alloted from PV1)
# lvextend –L +200M /dev/vg1/lv1 /dev/hda2
# mount /dev/vg1/lv1 /mnt/data
# df –ha ( TO CHECK )
Reduce LVM size:
# umount /mnt/data
# lvreduce –L -100M /dev/vg1/lv1
# mount /dev/vg1/lv1 /mnt/data
Some important commands
# pvscan pvdisplay
# vgscan vgdisplay
# lvscan lvdisplay
Software RAID
•
•
•
RAID is an acronym for ‘Redundant Array of inexpensive Disks” with software RAID,
the operating system combines multiple RAID partitions on different disks into a
single RAID device. (Linux also support Hardware RAID using special disk
controllers or external storage devices. These devices usually look like normal disks
or disk partitions to the installer0 The installer allows you to setup software RAID
devices. You first create RAID partitions by creating a partitions normally with a file
system type of “ software RIAD”. Then you click “RAID” button, and create a RAID
device from RAID type, but you will also need to assign a RAID device name
/dev/md0 and select RAID level each RAID level has different advantages and
disadvantages.
RAID level 0 is called “Stripping” : This type of RAID required at least two RAID
partitions. The resulting RAID device is a virtual partition the size of all the member
RAID partitions added together. RAID 0 allows creation of file system bigger than any
one disk and has high performance for read and writes . However , it is not truly a
redundant array: if any disk in the RAID device fails the file system on the RAID
device is destroyed.
RAID level 1 is called Mirroring: - It also requires two RAID partitions . The
resulting RAID device is a virtual partition the size of the smallest of the member
RAID partition. All RAID partitions which are members of RAID device contain
identical data. If any disk in the RAID device fails, the RAID device continues to
function without losing data. This is useful for fault tolerance, but cost in term of disk
space . Performance for reads and writes is good.
Software RAID
• RAID level 5 is called “striping with parity”: It requires at least three RAID
partitions of the same size. Like RAID 0 , this RAID level allows creation of
file system bigger than any one disk. However, additional parity data is also
stored on the RAID device which can be used to preserve file system data
even if a single disk in the RAID device fails. Therefore RAID 5 can survive
single disk failure, but at the cost of some storage efficiency. Read
performance is good but write performance is slower due to parity updates .
• Practical of RAID:
• Create three partitions change id to ‘fd’ for RAID
• # mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/hda1
/dev/hda2 /dev/hda3 “missing” (Meta disk administration)
• # mdadm - -details /dev/md0
• # mkfs.ext3 /dev/md0
• # mount /dev/md0 /mnt/data
• # vi /etc/fstab
• # /dev/md0 /mnt/data ext3 :wq
Managing RAID
• # mdadm --manage /dev/md0 - -fail /dev/hda1
• (in case any disk get fail in RAID 5 the above command can be used to
undetect that disk)
• # mdadm --manage /dev/md0 --remove /dev/hda1
• (To remove failed disk from RAID 5 partition)
• # mdadm --manage /dev/md0 --add /dev/hda4
• (can be used to add another disk to existing RAID 5 partition)
• To remove RAID Device
• # remove fstab entry
• # umount /dev/md0
• # mdadm --stop /dev/md0
• # mdadm --remove /dev/md0