LINUX
Presentation by Kallam Srinivas Reddy
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Overview of Linux System
Vi editor
Basic Commands
Redirect, Append, and Pipe
Relative & Absolut...
Overview of Linux System
Linux is an Operating system (OS).
Linux system is described as kernel & shell.
Kernel is the ...
Overview of Linux System
Multiuser & Multiprocess:
Many people can use one machine at the same time.

File & Process:
...
Overview of Linux System
Directory Structure
Files are put in a directory.
All directories are in a hierarchical structu...
Overview of Linux System
Directory Structure
Overview of Linux System
Important Directories:/bin- This contains files that are essential for correct operation of the
s...
Overview of Linux System
/dev- This contains various devices as files, e.g. harddisk, CDROM drive,
etc.
/root- This is the...
Overview of Linux System
Normal user and Super user
In Linux system, there is one special user for administration, who ca...
Overview of Linux System
Run levels in Linux- refers to the mode of operation in the Linux
operating systems
Following a...
Overview of Linux System
Following are the seven run levels in Red Hat Linux and Fedora
 0 ->halt
 1 ->Single user text...
VI Editor
• Programs & configuration files are text files.
• There are two popular text editors vi and Emacs.
• vi is a sc...
Basic Commands
How to run commands
When you log on Linux machine, you will see,
[cseos@hyperion001 srinu]$
 start typing...
Basic Commands
Options always start with “ - ”.
For Example
• cd ..
• ls –l .bashrc
• mv fileA fileB
Basic Commands
Basic useful Commands
 ls - show files in current position
 cd - change directory
 cp - copy file or dir...
Basic Commands
man - display online manual
su - switch user
 passwd - change password
 useradd - create new user accou...
Redirect, Append and Pipe
Redirect and append
 Output of command is displayed on screen by redirecting to a file.
 Using...
Redirect, Append and Pipe
Commands
head - show first several lines and omit other lines.
tail - show last several lines ...
Redirect, Append and Pipe
Using redirect.
->head 3 sample.txt
->head 3 sample.txt > redirect.txt
Using append.
->tail 3 sa...
Relative & Absolute Path
Path means a position in the directory tree.
 To express a path, you can use relative path or a...
File System & Partitions
Everything is a file in linux.
Mounting
Files related to mounting in linux
/etc/mtab(Current ...
File System & Partitions
Partitions
Commands to view existing partitions
 fdisk –l
 parted –l

Partition administrati...
File System & Partitions
Mounting Partitions:-

Temporary mounting
mount <device name> <directory name(mount point)>
Eg:-...
File System & Partitions
Mounting a partition using label
mount LABEL=<label name> <partition name>
Eg:- mount LABEL=os...
File System & Partitions
Components of LVM
Physical volume (PV)
Physical Extend (PE)
Volume Group (VG)
Logical Volume ...
File System & Partitions
lvresize – resizes a logical volume
lvreduce – reduces a logical volume
vgreduce – reduces a v...
Permissions
All the files and directories have the permissions and owner assigned
to them.
There are three types of perm...
Permissions
Commandschmod- change file mode, add or remove permission
chown- change owner of the file
Examplechmod a+w f...
Permissions
acl- access control lists
More secure way to secure the files.
The file system have to be mounted with the o...
Process Management
Process is a unit of running program.
Each process has some information, like process ID, owner, prio...
Process Management
Check your process.
ps
ps –u
Check process of all users.
top (To quit top, press “q”)
ps –e
ps –ef
Find...
Process Management
Output of “ top” command
User Management
Commands to know

whoami – Gives the current Username.
 who – gives the information about who is logged ...
User Management
Root user-The root user is also called the superuser is the most
powerful account on the Linux system(user...
User Management
Important files in user management/etc/shadow- User passwords are encrypted and kept in /etc/shadow
/etc/...
User Management
Commands for user management
useradd- to add a user
usermod – to modify the properties of a user
gpasswd ...
Group
Users can be listed in groups.
Groups allows you to set permissions on the group level instead of having to
set pe...
Software Management
RPM utility is used to manage soft wares in linux
RPM – Red Hat Package Manager
Tool used for install...
Software Management
 rpm –qf <package directory> > to install the package forcefully
 rpm –qlc <packager name>
> to see ...
Backup and restore
Backup using tar
 tar – cvf <destination and name to be> <source file>
>creating a tar backup
for sou...
Managing installed services
Services/programs
Two commands to control the services
1. Service
Temporary control(changes...
Managing installed services
2. Chkconfig
Permanent control(changes are carried until they are changed again no
matter of ...
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Linux

  1. 1. LINUX Presentation by Kallam Srinivas Reddy
  2. 2. • • • • • • • • • • • • • Overview of Linux System Vi editor Basic Commands Redirect, Append, and Pipe Relative & Absolute Path File System & Partitions Permissions Process Management User Management Group Software Management Backup and restore Managing installed services Outline
  3. 3. Overview of Linux System Linux is an Operating system (OS). Linux system is described as kernel & shell. Kernel is the main program of Linux system. It controls hardware, CPU, memory, hard disk, network card etc. Shell is an interface between user and kernel. Shell interprets your input as commands and pass them to kernel.
  4. 4. Overview of Linux System Multiuser & Multiprocess: Many people can use one machine at the same time. File & Process: Data, directory, process, hard disk etc (almost everything) are expressed as a file. Process is an running program identified by a unique id (PID).
  5. 5. Overview of Linux System Directory Structure Files are put in a directory. All directories are in a hierarchical structure (tree structure). User can create and remove any directories on the tree. Top directory is “/”, which is called slash or root. Users have the own directory. (home directory)
  6. 6. Overview of Linux System Directory Structure
  7. 7. Overview of Linux System Important Directories:/bin- This contains files that are essential for correct operation of the system. These are available for all users to use. /mnt- Provides a location for mounting devices, such as remote file systems and removable media /home- This is where user home directories are stored. /var- This directory is used to store files which change frequently, and must be available to be written to. /etc- Various system configuration files are stored here.
  8. 8. Overview of Linux System /dev- This contains various devices as files, e.g. harddisk, CDROM drive, etc. /root- This is the root (administrator) user's home directory /sbin- Binaries which are only expected to be used by the super user. /tmp- Temporary files. /boot Has the bootable Linux kernel and bootloader configuration files(GRUB) /usr- Contains user documentation, games, graphical files, libraries(lib),etc..
  9. 9. Overview of Linux System Normal user and Super user In Linux system, there is one special user for administration, who can do anything. This special user is called root or superuser. Case Sensitivity Linux operating system is case sensitive.
  10. 10. Overview of Linux System Run levels in Linux- refers to the mode of operation in the Linux operating systems Following are the run levels of some popular Linux versions Following are the seven run levels in Ubuntu  0 ->halt  1 ->Single user mode  2 ->Graphical multi-user with networking 3 – 5 -> Unused but configured the same as runlevel 2 6 -> Reboot
  11. 11. Overview of Linux System Following are the seven run levels in Red Hat Linux and Fedora  0 ->halt  1 ->Single user text mode(without networking)  2 ->Not used (user definable)  3 -> Full multi-user text mode  4 -> Not used (user definable)  5 -> Full multi-user graphical mode (with an X-based login screen)  6 -> Reboot
  12. 12. VI Editor • Programs & configuration files are text files. • There are two popular text editors vi and Emacs. • vi is a screen-oriented text editor originally created for the Unix operating system.
  13. 13. Basic Commands How to run commands When you log on Linux machine, you will see, [cseos@hyperion001 srinu]$  start typing the command next to the $ symbol  One command consists of three parts, i.e. command name, options, arguments. Between command name, options and arguments, space is necessary. For Example [srinu~]$ command-name optionA optionB argument1 argument2
  14. 14. Basic Commands Options always start with “ - ”. For Example • cd .. • ls –l .bashrc • mv fileA fileB
  15. 15. Basic Commands Basic useful Commands  ls - show files in current position  cd - change directory  cp - copy file or directory  mv - move file or directory  rm - remove file or directory  pwd - show current position  mkdir - create directory  rmdir - remove directory  cat - display file contents less - display file contents pagewise
  16. 16. Basic Commands man - display online manual su - switch user  passwd - change password  useradd - create new user account  userdel - delete user account  mount - mount a file system  umount - unmount a mounted file system  df - show disk space usage  shutdown - reboot or turn off machine
  17. 17. Redirect, Append and Pipe Redirect and append  Output of command is displayed on screen by redirecting to a file.  Using “>”, you can redirect the output from screen to a file.  Using “>>” you can append the output to the bottom of the file. Pipe  Some commands require input from a file or other commands.  Using “|”, you can use output from other command as input to the command.
  18. 18. Redirect, Append and Pipe Commands head - show first several lines and omit other lines. tail - show last several lines and omit other lines. grep - show lines matching a pattern Working with commands: In home directory, type ->ls .bash_profile ->cp .bash_profile sample.txt ->less sample.txt
  19. 19. Redirect, Append and Pipe Using redirect. ->head 3 sample.txt ->head 3 sample.txt > redirect.txt Using append. ->tail 3 sample.txt tail 3 ->sample.txt >> redirect.txt less redirect.txt Using pipe. less redirect.txt grep PATH redirect.txt tail redirect.txt | grep PATH rm sample.txt rm redirect.txt
  20. 20. Relative & Absolute Path Path means a position in the directory tree.  To express a path, you can use relative path or absolute path. In relative path expression, the path is not defined uniquely, it depends on your current path.  In absolute path expression, the path is defined uniquely, it does not depend on your current path.
  21. 21. File System & Partitions Everything is a file in linux. Mounting Files related to mounting in linux /etc/mtab(Current files mounted) /etc/fstab(info about permanent mounting points)
  22. 22. File System & Partitions Partitions Commands to view existing partitions  fdisk –l  parted –l Partition administration using fdisk fdisk <partition name with location> eg:- fdisk /dev/sda. Various options for fdisk are n,p,q,t,v,w,etc.. Updating the partition without restarting :partrobe /dev/sda or partx /dev/sda Formatting a partition with file systems(eg- ext4 system) mkfs.<file system type> <partition name> Eg - mkfs.ext4 /dev/sda Note:-After formatting the partition must me mounted in ordered to use
  23. 23. File System & Partitions Mounting Partitions:- Temporary mounting mount <device name> <directory name(mount point)> Eg:- mount /dev/sda oslab Permanent mounting Add the parameters for mounting point in the file /etc/fstab as follows Umounting the partition umount <mount point directory> Eg:- umount /oslab To view mount points use the command mount Assigning label to the partition(giving some name to partition) e2label <partition name> <label> Eg:- e2label </dev/sda> <os>
  24. 24. File System & Partitions Mounting a partition using label mount LABEL=<label name> <partition name> Eg:- mount LABEL=os /oslab LVM(Logical volume management)
  25. 25. File System & Partitions Components of LVM Physical volume (PV) Physical Extend (PE) Volume Group (VG) Logical Volume (LV) Logical Extend (LE) Commands in LVM pvs, vgs, lvs – displays all PVs, VGs, and LVs in the system Display detailed information pvdisplay, vgdisplay, lvdisplay  creating PVs, VGs, LVs pvcreate, vgcreate, and lvcreate
  26. 26. File System & Partitions lvresize – resizes a logical volume lvreduce – reduces a logical volume vgreduce – reduces a volume group Removing/deleting PVs, VGs, LVs pvremove, vgremove, lvremove
  27. 27. Permissions All the files and directories have the permissions and owner assigned to them. There are three types of permission readable, writeable and executable. Permissions are given to three kinds of groups namely owner, group member and others. Example[cswug@hyperion001 cswug]$ ls l .bash_profile -rw-r--r-- 1 cswug cswug 191 Jan 4 13:11 .bash_profile Note-r : readable, w:writable, x: executable
  28. 28. Permissions Commandschmod- change file mode, add or remove permission chown- change owner of the file Examplechmod a+w filename - add writable permission to all users chmod o-x filename - remove executable permission from others Note- u: user (owner), g: group, o: others a: all
  29. 29. Permissions acl- access control lists More secure way to secure the files. The file system have to be mounted with the option acl in /etc/fstab file. Files with acls can be read only using the getfacl command. Writing or changing acls can be done with setfacl or /usr/bin/setfacl. To remove an acl of a file system use –x option for setfacl command.
  30. 30. Process Management Process is a unit of running program. Each process has some information, like process ID, owner, priority, etc. CommandsKill - Sends specified signal to specified process .The process is specified by process ID. Killall – kills all the process with a particular name. The program is specified by command name. ps - Show process status top - Show system usage statistics
  31. 31. Process Management Check your process. ps ps –u Check process of all users. top (To quit top, press “q”) ps –e ps –ef Find your process. ps –ef | grep cseos
  32. 32. Process Management Output of “ top” command
  33. 33. User Management Commands to know whoami – Gives the current Username.  who – gives the information about who is logged on the system.  who am i – gives the details about current session in a line.  w – shows you who is logged on and what they are doing.  id – gives the user id, primary group id, and a list of the groups that you belong to.
  34. 34. User Management Root user-The root user is also called the superuser is the most powerful account on the Linux system(userid 0) User management on any Unix can be done in three ways. 1. Graphical 2. Command line tools 3. Edit the local configuration files
  35. 35. User Management Important files in user management/etc/shadow- User passwords are encrypted and kept in /etc/shadow /etc/passwd –Contains the local user database on Linux /etc/default/useradd - contains some default user options. Home directories(Two ways of creating home directories) 1. useradd –m to create a home directory for user. 2. Create a directory using mkdir and setting the owner as user using chmod and restricting the permissions.
  36. 36. User Management Commands for user management useradd- to add a user usermod – to modify the properties of a user gpasswd – to manage the users userdel – to delete a user passwd – to manage passwords for users). chage – to change the attributes of the passwords of users su – allows a user to run a shell of other users Sudo-The sudo program allows a user to start a program with the credentials of another user.
  37. 37. Group Users can be listed in groups. Groups allows you to set permissions on the group level instead of having to set permissions for every individual user. /etc/group – file in which group membership is defined. Commands for group management group – to view the list of groups to which user belongs to. groupadd – to add new groups usermod - Group membership can be modified groupmod – to change the group name groupdel – to remove a group permanently
  38. 38. Software Management RPM utility is used to manage soft wares in linux RPM – Red Hat Package Manager Tool used for installing, uninstalling, verifying, querying, and updating software packages. Commands for RPM  rpm –qa (q- query and a- all) > gives all the installed packages on the system  rpm –q <package name> > to check whether a package is installed or not.  rpm –ivh <package name> > to install a package(i-install, v- verbose view, hhash progress) Note:- to install a package, first navigate to the directory in which packages are stored  rpm –e <package name> >to uninstall/ remove a package(e- erase)
  39. 39. Software Management  rpm –qf <package directory> > to install the package forcefully  rpm –qlc <packager name> > to see the configuration files of installed package(q-query, l-local, c-configuration)  rpm –qld <package name> > to see which directory is associated with a particular package (q-query, l- local, d- directory) Dependency- some packages requires some other packages to be installed before it can be installed.  rpm -ivh <package name> --nodeps > to install packages without dependicies.  rpm -uvh <package name> > to update a package(u- update, v-verbose, h-hash progress)
  40. 40. Backup and restore Backup using tar  tar – cvf <destination and name to be> <source file> >creating a tar backup for source file (note: c-create, v-verbose, f-name of tar file) eg:- tar – cvf /opt/etc.tar /etc  gzip <file name> >applying gzip on the tar file eg:- gzip /opt/etc.tar  scp <gzip file> <destination address> > transferring the file to another system using secure copy (scr) (destination address is the IP address of the target system followed by the target directory) eg:- scp /opt/etc.tar.gz 192.XXX.XX.X/root/  gunzip <file name> > to unzip the file  tar – xvf <file name> > to untar the file (x-remove) eg:- tar – xvf etc.tar
  41. 41. Managing installed services Services/programs Two commands to control the services 1. Service Temporary control(changes only for current session / after booting the changes will be erased from the service) Commands  service <name of the service> status -> used to check the status of the service service <name of the service> start -> used to start the service service <name of the service> stop -> used to stop the service service <name of the service> reload -> used to reload the service service <name of the service> restart -> used to restart the service
  42. 42. Managing installed services 2. Chkconfig Permanent control(changes are carried until they are changed again no matter of booting). Commands  chkconfig - - list >to check the availability of the service chkconfig <service> on > to make the service available after restart chkconfig <service> off > to make the service unavailable after restart
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