Linux System commands Essentialsand Basics.pptx

What is Linux
• Advanced Features of Servers:
• Clustering
• Virtualization
• Cloud Computing
• Real-time computing
• Specialized storage

Linux System
Architecture
• Hardware layer – Hardware consists of all
peripheral devices (RAM/ HDD/ CPU etc)
• Kernel – Core component of Operating System,
interacts directly with hardware, provides low
level services to upper layer components
• Shell – An interface to kernel, hiding complexity of
kernel’s functions from users. Takes commands
from user and executes kernel’s functions
• Utilities – Utility programs giving user most of the
functionalities of an operating systems

Linux Directory Structure
Linux File System

Print current path and Manual
Open the Terminal
# pwd (prints the working directory)
# man <command> (To display the help for the
command)
e.g. # man grep
# ls
ls lists all the files in the current directory

Vi Editor
Command
Mode
Input
Mode
Last-Line
Mode
Insert (i, I)
Esc
Return
:
vi Editing modes
w to save
q to quit
wq to save and quit
q! to quit without saving

Vi Editor
Starting the Vi editor
Vi lets you create new files or edit existing files.
Command to start Vi : vi
Opening an existing file/creating a new file
vi filename
Press I to get into the Insert Mode and start typing
Press Esc to get back to the Command Mode

Vi Editor
Last line Mode
:q :- Quit the editor
:q! :- Quit the editor without saving the changes to the file.
:wq :- quit and save
:w :- only save
To go to a specific line in the file
:linenumber

Vi Editor
Cutting text
d^
Deletes from current cursor position to the
beginning of the line
d$
end of the line
dw
end of the word
dd – Delete 1 line
Ndd
Deletes one line from current cursor position.
Specify count to delete many lines. Use ‘p’ to paste the lines if
required

Vi Editor
Yanking and Pasting
yl
yank a single character. Specify count to yank
more characters
yw
yank a single word. Specify count to yank more
words
yy
yank a single line. Specify count to yank more
lines
Nyy
N indicates number of lines
p
paste the text that was either deleted or yanked
previously

Vi Editor
String Search
/pattern : search forward for the pattern
?pattern : search backward for the pattern
e.g. /error will find the word ‘error’ in the file.
Use ‘n’ to iterate through the search result
Undo and Redo
Press u in the command mode to undo
Press ctrl+r in the command mode to redo

Navigate the file system using cd – change directory
1. cd documents/work/accounting (change to relative path)
2. cd / (change to root partition /)
3. cd .. (change up one level of directory)
4. cd ~ (change to current user’s home directory)
Create a Directory using mkdir
5. mkdir newdir
6. mkdir –p /root/newdir/subdir
Linux File System

To create an empty (zero byte) file:
$ touch filename
To create multiple such files:
$ touch file1 file2 file3
$ touch file{1..5}.sh
Touch Command

Cat
# cat filename - It allows to view the contents of a file
#cat file1 > file2
> redirect and overwrite
>> redirect and append
Files and Directory

# less filename (To view a file one page at a time)
# more filename (To view a file one page at a time)
# tac filename (To view files in a reverse order)
Press q to quit
#cmd1 | cmd2 | cmd3
This will execute as follows :
--> cmd1
--> cmd2 <o/p_cmd1>
--> cmd3 <o/p_cmd2>
Files and Directory

Copy and Move Files
Copy files from source to destination
cp source destination
e.g.
cp sample.txt /home/training/
cp –r sourcefolder destinationfolder
Move files from source to destination – cut and paste
mv source destination
e.g.
mv sample.txt /home/training

Copy and Move Files
i -- interactive. Prompts you to confirm if the file is going to overwrite
a file in your destination. This is a handy option because it can help
prevent you from making mistakes.
-r -- recursive. Rather than just copying all the files and directories,
copies the whole directory tree, subdirectories and all, to another
location.
-f -- force. Copies without prompting you for confirmation that the file
should be overwritten. Unless you're sure you want to force the
copy, you probably don't want to make friends with this option
right now.
-v - verbose. Will show the progress of the files being copied.

Remove
# rm filename (To delete a file)
# rm file1 file2 file3 (To delete multiple files)
# rmdir dirname (To delete a empty folder only)
# rm -rfv foldername
(To delete a folder & it's content recursively &
with verbose)
-r = recursive
-f = forcefully
-v = Verbose

Identifying file type
ls -l shows the file type in the 1st character of line.
For example.
#ls -l /dev
-rw-rw----. 1 root disk 8, 0 Mar 16 08:03 /dev/sda
i> Regular Files
These are normal files. (represented as '-' in ls -l o/p )
ii> Directory files
These are directories. (represented as 'd' in ls -l o/p )
iii> Link Files (Symlinks)
This are links(shortcut) . (represented as 'l' in ls -l o/p )

Identifying file type
There are 2 types of device files .
iv> Character Files (represented as 'c' in ls -l o/p ) Kernel
communicates with these devices in character size data (1byte).
v> Block Files (represented as 'b' in ls -l o/p )
Kernel communicates with these devices in block size data (512byte).
vi> Socket Files (represented as 's' in ls -l o/p Used
for communication .
vii> Pipe Files (represented as 'p' in ls -l o/p )

Date, hwclock, calendar
# date (To to show current date & time)
# date -s 12:00 (To change time)
# date -s YYYY-MM-DD (To change date)
# date MMDDhhmmYYYY (To change time & date together)
MM - Month
DD - date
hh - hours
mm - minute
YY - years

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Head, Tail and Word Count
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# head filename (To read top 10 lines from a file)
# head -n 15 filename (To read top 15 lines from a file)
# tail filename (To read bottom 10 lines from a file)
# tail -n 15 filename (To read bottom 15 lines from a file)
# tail -f /var/log/message (This is will continuously show updates from the file
until you pressed `Ctrl+c'
# wc filename (print the number of newlines, words, and bytes in files)

grep
grep --> general regular expression processor
Syntax:
#grep searchpattern filename
#grep error /var/log/syslog
# grep bash /etc/passwd (To search a bash word in a file)
-v --> returns lines do not contain the pattern
-n --> precede returned lines with line numbers
-c --> only return a count of lines with the matching pattern
-r --> perform a recursive search of files, starting with the named directory
-l --> Use along with “-r” , only returns the names of files that have at least
one line containing the pattern
-w --> Display only lines having the exact search pattern
-i --> perform a case-insensitive search
grep

# grep -r useradd /
# grep -rli useradd /root/samnotes
# grep -E "word1|word2|word3|word4" /etc/passwd
(To search two or more than two words by using grep)
# egrep "bash|nologin" /etc/passwd
(To search two or more than two words by using grep)
grep

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grep
Anchors match the beginning or end of a line or word
^ --> Line begins with
$ --> Line ends with
--> Escape Character
bc --> word begins with ‘c’
cb --> word ends with ‘c’
b is a regular expression to indicate any word
e.g.
$ grep -E “ba” file1
This is arjun
A is for apple
$ ls -al | grep ^d (It will list only Directories)

grep
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Pipe output to grep
#service sshd start
#netstat -a | grep 22
There are different types of data:-
# ls -al | grep ^- (It will list only Normal files)
# ls -al | grep ^d (It will list only Directories)
# ls -al | grep ^c (It will list only Character files)

# ls -al | grep ^- | wc -l (It will list only normal
files & will count no. of files)
#ls –l | grep .txt$
Note : - We can use grep along with color by
using following options.
#ls -al | grep --color=always ^-
grep

Type ls –l <filename/dirname> to check the permissions
Default file permission for the super user
---------------------------------------------
rwx----> owner/user who is created the file or dir
rx----> group to which owner belongs to
rx----> other people
r----> read --->4
w----> write --->2
x----> execute --->1
drwx r-x r-x ------>755---->default permission of directory
U G O
-rw-r--r----> 644----> default permission of file
File Permission

File Permission
File permissions are assigned to:
1. the owner of a file
2. the members of the group the file is assigned to
3. all other users
4. Permissions under Linux are configured for each file and directory.

There are three levels of permissions:
1. The permissions that apply to the owner of the file. The owner of a
file is by default the user that created the file1.
2. The permissions that apply to all members of the group that is
associated with the file.
3. The permissions that apply to all other users on the system.
4. Permissions can only be changed by the owner, and root of course.
File Permission

File permission for the normal user
rwxrwxr-x ----->4+2+1 4+2+1 4+1----->775----default permission of
directory
-rw-rw-r-- ---->4+2 4+2 4 ----->664---->default permission of a file
File Permission

read = 4
write = 2
execute= 1
chmod 777 <file>/<directory>
chmod u=rwx,g=rwx,o=rwx <file>/<directory>
chmod g-w,o-w <file>/<directory>
chmod u+x <file>/<directory>
File Permission

= overwrite
- remove
+ append
chmod ugo=rwx perm
OR
chmod a=rwx perm
File Permission

Changing ownership of folder or file
chown owner <file/folder>
chown sam backup
Note :- In above example sam is an owner of backup folder
chown owner.groupowner <file/folder>
chown owner:groupowner <file/folder>
chown sameer.sameer backup
chown sameer:sameer backup
Changing group ownership of folder or file
chgrp grpname <file/folder>
chgrp sam backup
File Permission

Exercise
Create 2 folders under /
Create 4 users and 2 groups
Map users 1,2 to group 1 and users 3,4 to group 2
User 1 should be able to read,execute and write files in both folders.
Group 2 must be able read,execute and write in folder 2. All others have
read and execute only permission for both folders.

DF
The df (disk free) program shows you the size, used space, and free
space on a given disk partition
# df –h
displays the result in human readable format
du
Displays the amout of Disk Usage for the specified files and folders
e.g. # du folder1
Show the size of specific files/directory
$du –h file1 file2
$du –h directory
List the sizes of all files inside the directory
$du –a directory
Free
Free show the Memory statistic like the RAM free space
# free
Disks and Filesystems

Fdisk
The fdisk command is a text-based utility for viewing and managing hard disk
partitions on Linux.
List Partitions
#fdisk -l commands lists the partitions on your system.
Entering Command Mode
To work on a disk’s partitions, you have to enter command mode. You’ll need the
device name of a disk from the fdisk -l command. The following command enters
command mode for the first disk device:
#fdisk /dev/sda
Using Command Mode
In command mode, you use single-letter commands to specify actions you want to
take. Type m and press Enter to see a list of the commands you can use.

Using fdisk to create a new partition:
• Type n for creating a new partition
• Type p for primary partition
• Type 1 for choosing the partition number
• Give default for first sector and +sizeM (e.g. +500M) for last sector
• Type w to save changes
• Use fdisk –l to see the partition

Formatting a Partition
You must format new partitions with a file system before you can use
them. You can do this with the appropriate mkfs command. For
example, this command formats the fifth partition on the first disk with
the ext4 file system.
mkfs.ext4 /dev/sda5

mount
mount [options] device directory
The mount command makes a partition accessible. Most commonly
it handles disk drives (say, /dev/sda1) and removal media (e.g., USB
keys), making them accessible via an existing directory (say, /mnt/
mydir):
# mkdir /mnt/mydir
# ls /mnt/mydir
# mount /dev/sda1 /mnt/mydir
# ls /mnt/mydir
# df /mnt/mydir
Or
#df -h
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 1011928 285744 674780 30% /mnt/mydir

umount
umount [options] [device | directory]
umount does the opposite of mount: it makes a disk partition
unavailable via the filesystem. For instance, if you’ve mounted a
CD-ROM disc, you can’t eject it until it’s umounted:
$ umount /media/cdrom
Always unmount a removable medium before ejecting it or you risk
damage to its filesystem. To unmount all mounted devices:
# umount -a
Don’t unmount a filesystem that’s in use; in fact, the umount command
will refuse to do so for safety reasons.

FSTAB
/etc/fstab file is used to control what file systems are mounted when
the system boots, as well as to supply default values for other file
systems that may be mounted manually from time to time

1st Column :
~~~~~~~~~~
The first column contains the partitions's label, eg. "LABEL=/boot" or
driver's path, eg. "/dev/cdrom". Device driver's path tells the system to
mount the device with the mentioned device driver.
2nd Column :
~~~~~~~~~~
The second field (fs_file) describes the mount point for the
filesystem.For swap partitions, this field should be specified as `none'.
If the name of the mount point contains spaces these can be escaped as
`040'.
FSTAB

3rd Column :
~~~~~~~~~~
The third column in the file specifies the file system type of the
device or partition. Many diffrent file systems are supported by Linux
and most common ones are,
1) autofs
2) devpts
3) ext2
4) ext3
5) iso9660
6) nfs
7) Ntfs
8) proc
9) swap
FSTAB

10) tmpfs
11) udf
12) ufs
13) vfat
14) xfs
If you are not sure of the file system type of the device then set the
value to "auto" and the system will itself determine the file system type
andwill mount the device with that file system.
FSTAB

4th Column :
~~~~~~~~~~
The fourth column is for permissions to be given to the partition at
the
time of booting. There are many options which constitutes the forth
column.
They are as follows : -
1) ro - Read Only
2) rw - Read Write
3) auto - Mount on startup
4) noauto- Do not mount on startup
5) user - Any user can mount, but only unmount device mounted by him
6) nouser- Only root can mount & unmount the device
7) users - Every user can mount and also unmount the device mounted
by others
8) owner - Same as user (above no. 5)
FSTAB

9) dev - User can use device driver to mount the device
10) nodev - User cannot use device driver to mount the device
11) exec - Users can execute binaries on the partition
12) noexec- Users cannot execute binaries on the partition
13) async - Asynchronous, whenever a file is saved it will be first saved
in the RAM and after 30 seconds all the queued files will be
written on the hard disk
14) sync - Synchronous, whenever a file is saved it will be directly
written to the hard disk
15) suid - Allow set-user-identifier for the device where users are
allowed to run binaries even though they do not have execute
permissions.
16) nosuid- Do not allow set-user-identifier
17) auto, rw, dev, async, suid, exec & nouser
FSTAB

5th Column :
~~~~~~~~~~
The 5th column is for backup option. This column contains either 0 or
1. Where "0" stands for "NO" and "1" stands for "YES".
6th Column :
~~~~~~~~~~
The 6th column is for "fsck" option. fsck stands for file system
check. This column defines the order in which the system should scan
the partitions on start up.
FSTAB

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Performance Monitoring
Viewing Processes
ps
ps [options]
The ps command displays information about your running processes, and optionally
the processes of other users.
Type the following to see every process in the system
$ps -ef
To view your processes:
$ ps -ux
ps -U smith - display processes of user Smith
you can extract information more finely from the output of ps using grep and other
filter programs:
$ ps -ux | grep myprogram

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top
top [options]
The top command lets you monitor the most active processes, updating the display at
regular intervals (say, every second). It is a screen-based program that updates the
display in place, interactively.
$ top
While top is running, you can press keys to change its behavior, such as setting the
update speed (s), hiding idle processes (i), or killing processes (k). Type h to see a
complete list and q to quit.
Useful options
-nN Perform N updates, then quit.
-dN Update the display every N seconds.
-pN -pM ... Display only the processes with PID N, M, ..., up to 20 processes.
-b Print on standard output noninteractively, without playing screen
tricks.
#top -b -n1 > outfile saves a quick snapshot to a file.

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kill [options] [process_ids]
The kill command sends a signal to a process. This can terminate a process (the default
action), interrupt it, suspend it, crash it, and so on. You must own the process, or be
the superuser, to affect it.
To terminate process 13243, for example, run:
$ kill 13243
If this does not work—some programs catch this signal without
terminating—add the -KILL or (equivalently) -9 option:
$ kill -9 13243

YUM
# yum install <package name> Will install the package
# yum install * --> This will install everything
# yum update To update all packages
# yum update <package name> ----> To update selected package
# yum provides <file_path> --->> Shows which package provides
that file.
# yum clean all --->> To clean all packages in yum cache
# yum remove <package name – this will remove package specified
# yum -y remove *.* ---> this will remove everything
# yum list nfs* ---> this will list package details
# yum list all --> To list all packages available
#yum info | grep jdk
This will list all packages available in repo that have the
keyword jdk
# yum grouplist

Red Hat Package Manager
RPM stands for Red Hat Package Manager.
1. Installing a RPM package Using rpm –ivh
RPM filename has packagename, version, release and architecture
name.
For example, In the MySQL-client-3.23.57-1.i386.rpm file:
MySQL-client – Package Name
3.23.57 – Version
1 – Release
i386 – Architecture

# rpm -ivh MySQL-client-3.23.57-1.i386.rpm
Preparing...
########################################### [100%]
1:MySQL-client
########################################### [100%]
rpm command and options
-i : install a package
-v : verbose
-h : print hash marks as the package archive is unpacked.

2. Query all the RPM Packages using rpm –qa
You can use rpm command to query all the packages installed in your
system.
# rpm -qa
cdrecord-2.01-10.7.el5
bluez-libs-3.7-1.1
setarch-2.0-1.1
.
.
-q query operation
-a queries all installed packages

To identify whether a particular rpm package is installed on your
system
# rpm -qa | grep 'cdrecord‘
3. Query a Particular RPM Package using rpm –q
# rpm -q MySQL-client
MySQL-client-3.23.57-1
# rpm -q MySQL
package MySQL is not installed

4. Query RPM Packages in a various format using rpm –queryformat
# rpm -qa --queryformat '%{name-%{version}-%{release} %{size}n'
cdrecord-2.01-10.7 12324
bluez-libs-3.7-1.1 5634
setarch-2.0-1.1 235563
.
.
#
5. Which RPM package does a file belong to? – Use rpm –qf
# rpm -qf /usr/bin/mysqlaccess
MySQL-client-3.23.57-1
-f : file name

6. Information about Installed RPM Package using rpm –qi
# rpm -qi MySQL-client
Name : MySQL-client Relocations: (not relocatable)
Version : 3.23.57 Vendor: MySQL AB
Release : 1 Build Date: Mon 09 Jun 2003 11:08:28 PM CEST
Install Date: Mon 06 Feb 2010 03:19:16 AM PST Build Host: build.mysql.com
Group : Applications/Databases Source RPM: MySQL-3.23.57-1.src.rpm
Size : 5305109 License: GPL / LGPL
Signature : (none)
Packager : Lenz Grimmer
URL : http://www.mysql.com/
Summary : MySQL - Client
Description : This package contains the standard MySQL clients.

7. List the Dependency Packages using rpm –qRP
# rpm -qRp MySQL-client-3.23.57-1.i386.rpm
/bin/sh
/usr/bin/perl
8. Upgrading a RPM Package using rpm –Uvh
# rpm -Uvh MySQL-client-3.23.57-1.i386.rpm
Preparing...
########################################### [100%]
1:MySQL-client
###########################################
9. Uninstalling a RPM Package using rpm –e
# rpm -ev MySQL-client

Services
# apt-get install –y apache2
# service apache2 start
# service apache2 status
# service apache2 restart
# service apache2 stop
# service –-status-all
#systemctl start SERVICE - Use it to start a service. Does not persist after reboot
#systemctl stop SERVICE - Use it to stop a service. Does not persist after reboot
#systemctl restart SERVICE - Use it to restart a service
#systemctl status SERVICE - Shows the status of a service. Tells whether a service is currently running.
#systemctl enable SERVICE - Turns the service on, on the next reboot or on the next start event. It persists
after reboot.
#systemctl disable SERVICE

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IP Addressing
To check the IP Address
#ifconfig <name of interface> or just ifconfig
Or
#ip a
For temporary ip address assignment:
#sudo ifconfig <name of interface> 10.9.49.112 netmask 255.255.255.0
e.g.
#ifconfig eth0 10.9.49.112 netmask 255.255.255.0
To disable a network interface:
ifconfig <name of interface> down
To enable a network interface
Ifconfig <name of interface> up

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IP Addressing
To configure a default gateway, you can use the route command in the following
manner.
sudo route add default gw 10.0.0.1 <name of interface>
Check the default gateway configuration using router command
route –n
Edit /etc/resolv.conf for assigning temporary dns servers
nameserver 8.8.8.8
nameserver 4.2.2.1
To purge all ip configuration
Ip a flush <name of interface>
#ifdown <name of interface>
#ifup <name of interface>

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IP Addressing
For permanent IP Address assignment, edit /etc/network/interfaces
iface <name of interface> inet static
address 192.168.3.3
netmask 255.255.255.0
gateway 192.168.3.1
dnssearch example.com sales.example.com dev.example.com
dnsnameservers 192.168.3.45 192.168.8.10
#ip a flush <name of interface>
To change back to a dhcp client
iface <name of interface> inet dhcp
To renew the dhcp client IP
#dhclient
For adding host names, edit /etc/hosts

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IP Addressing
For permanent IP Address assignment in CentOS, edit vi /etc/sysconfig/network-scripts/ifcfg-enp0s3
HWADDR=08:00:27:98:06:76
TYPE=Ethernet
# Static IP Address #
BOOTPROTO=none
IPADDR=192.168.1.10
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
DNS1=192.168.1.1
DNS2=8.8.8.8
#ip a flush <name of interface>

Lsof – List Open Files
Lsof command used in many Linux/Unix like system that is used to
display list of all the open files and the processes. The open files
included are disk files, network sockets, pipes, devices and processes.

In the below example, it will show long listing of open files some of them are
extracted for better understanding which displays the columns
like Command, PID, USER, FD, TYPE etc.
FD – stands for File descriptor and may seen some of the values as:
cwd current working directory
rtd root directory
txt program text (code and data)
mem memory-mapped file
Also in FD column numbers like 1u is actual file descriptor and followed by u,r,w of it’s
mode as:
r for read access.
w for write access.
u for read and write access.
TYPE – of files and it’s identification.
DIR – Directory
REG – Regular file
CHR – Character special file.
FIFO – First In First Out

To display list of all open files with the
user ‘training’:
#lsof –u training
Find processes using specific port
number 22
#lsof –i TCP:22
List all connections
#lsof -i
List all open files of specific device
#lsof /dev/sda1
Exclude User with ‘^’ Character
#lsof –i –u^root
Find the commands used by specific user
#lsof –i –u training
List open files of specific file system (/proc)
#lsof /proc
List all files opened by specific process id
#lsof –p 12434

Tcpdump – Network Packet Analyzer
Tcpdump one of the most widely used command-line network packet
analyzer or packets sniffer program that is used capture or filter TCP/IP
packets that received or transferred on a specific interface over a
network.

Netstat – Network Statistics
Netstat is a command line tool for monitoring incoming and outgoing
network packets statistics as well as interface statistics. It is very useful
tool for every system administrator to monitor network performance
and troubleshoot network related problems

Network Commands
ssh [options] host [command]
The ssh (Secure Shell) program securely logs you into a remote machine where you
already have an account:
$ ssh remote.example.com
Alternatively, it can invoke a program on that remote machine
without logging you in:
$ ssh remote.example.com who
$ssh smith@server.example.com specify the user smith while connecting

Network Commands
scp local_spec remote_spec
The scp (secure copy) command copies files and directories from one computer to another in
batch.
It encrypts all communication between the two machines.
As a simple example, scp can copy a local file to a remote machine:
$ scp myfile remote.example.com:newfile
recursively copy a directory to a remote machine:
$ scp -r mydir remote.example.com:
copy a remote file to your local machine:
$ scp remote.example.com:myfile .
or recursively copy a remote directory to your local machine:
$ scp -r remote.example.com:mydir .
‘.’ in the above 2 examples indicates that the destination folder in the local machine is
the current folder

Run Levels
A runlevel is a preset operating state on a Unix-like operating system.
A system can be booted into (i.e., started up into) any of several runlevels, each of which is represented by a single
digit integer. Each runlevel designates a different system configuration and allows access to a different combination of
processes (i.e., instances of executing programs).
The are differences in the runlevels according to the operating system. Seven runlevels are supported in the standard
Linux kernel (i.e., core of the operating system). They are:
0 - System halt; no activity, the system can be safely powered down.
1 - Single user; rarely used.
2 - Multiple users, no NFS (network filesystem); also used rarely.
3 - Multiple users, command line (i.e., all-text mode) interface; the standard runlevel for most Linux-based server
hardware.
4 - User-definable
5 - Multiple users, GUI (graphical user interface); the standard runlevel for most Linux-based desktop systems.
6 - Reboot; used when restarting the system.
By default Linux boots either to runlevel 3 or to runlevel 5. The former permits the system to run all services except
for a GUI. The latter allows all services including a GUI.
In addition to the standard runlevels, users can modify the preset runlevels or even create new ones if desired.
Runlevels 2 and 4 are usually used for user defined runlevels.

Boot and Shutdown
$init 0 - shutdown
$init 6 -restart
$sudo shutdown -h 09:30 "Going down for scheduled maintenance.
Expected downtime is 1 hour.“
h stands for Halt
$sudo shutdown –r
r is for Restart

Servers
• Samba Sever
• Web server
• Application server
• NFS server
• DNS
• DHCP
• Database server

Linux System commands Essentialsand Basics.pptx

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