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![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](https://image.slidesharecdn.com/linux-131130130209-phpapp02/75/Linux-13-2048.jpg)
![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](https://image.slidesharecdn.com/linux-131130130209-phpapp02/75/Linux-27-2048.jpg)
Uploaded bySrinivas Reddy
Linux
The document provides an overview of the Linux operating system. It discusses key Linux concepts like the kernel, shell, file structure, users and permissions. It also summarizes common Linux commands for file management, editing, users, groups, software installation and services. Key tools covered include vi editor, rpm, tar, useradd/del, service and chkconfig. The document is intended as part of an introductory Linux presentation.
Linux
- 1. LINUX Presentation by KallamSrinivas Reddy
- 2. • • • • • • • • • • • • • Overview of LinuxSystem 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. Overview of LinuxSystem 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. Overview of LinuxSystem 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. Overview of LinuxSystem 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. Overview of LinuxSystem Directory Structure
- 7. Overview of LinuxSystem 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. Overview of LinuxSystem /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. Overview of LinuxSystem 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. Overview of LinuxSystem 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. Overview of LinuxSystem 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. 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. Basic Commands How torun 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. Basic Commands Options alwaysstart with “ - ”. For Example • cd .. • ls –l .bashrc • mv fileA fileB
- 15. Basic Commands Basic usefulCommands 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. 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. Redirect, Append andPipe 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. Redirect, Append andPipe 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. Redirect, Append andPipe 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. Relative & AbsolutePath 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. 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. 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. 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. File System &Partitions Mounting a partition using label mount LABEL=<label name> <partition name> Eg:- mount LABEL=os /oslab LVM(Logical volume management)
- 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. 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. Permissions All the filesand 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. Permissions Commandschmod- change filemode, 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. Permissions acl- access controllists 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. Process Management Process isa unit of running program. Each process has some information, like process ID, owner, priority, etc. CommandsKill - 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. Process Management Check yourprocess. 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. Process Management Output of“ top” command
- 33. User Management Commands toknow 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. User Management Root user-Theroot 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. User Management Important filesin 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. User Management Commands foruser 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. Group Users can belisted 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. Software Management RPM utilityis 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. 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. Backup and restore Backupusing 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. Managing installed services Services/programs Twocommands 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. 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