Three types of permission read write and execute, Ever file and folder have three relations owner group and

others

[ Read = r write = w execute = x ] [ owner = u group = g other = o ]

[root@pc1 ~] # Ls -Ld /disk

1= nature of object [d=dir -=file L=link]

2= first three permission for owner [ rwx ]

3= second three permission for group members [ r-x]

4= third three permission for others [r-x]

5= number of inodes contain by this directory

6= owner of directory

7= group of directory

8= size of directory

9= creating date of object

10= name of object

[root@pc1 ~] # Ls -L /disk

Drwxr-xr – x 2 root root 4096 Jan 1 1988 dir1

Drwxr-xr – x 2 root root 4096 Jan 1 1988 dir2

Drwxr-xr – x 2 root root 4096 Jan 1 1988 dir3

Changing permission = give write permission to other on /disk

[root@pc1 ~] # chmod 0+w /disk

Give read write and execute permission for group on /disk

[root@pc1 ~] # chmod g+rwx /disk

Assigning read writ and execute permission to user, group and other with single command

[root@pc1 ~] # chmod u+rwx , g+rwx, o – rwx /disk

Assigning different permission with different commands which separate with semicolon

[root@pc1 ~] # chmod u+rwx /disk ; chmod g+rwx /disk ; chmod 0+rx /disk

Using number system =----- [ Read = 4 ] [ Write = 2 ] [ Execute = 1 ]

rwx=7

r-x=5

---=0

Assigning full permission to owner and no permission for group and others

[root@pc1 ~] # chmod 700 /disk

Assigning full permission for owner and group no permission for other

[root@pc1 ~] # chmod 700 /disk

Assigning full permission to all

[root@pc1 ~] # chmod 777 /disk

Assigning full permission for owner and read, and execute for group and others

[root@pc1 ~] # chmod 755 /disk

Assigning no permission for all

[root@pc1 ~] # chmod 000 /disk

Assigning sticky bit permission for other

[root@pc1 ~] # chmod o+t /disk

Assigning suid permission for owner

[root@pc1 ~] # chmod u+s /disk

Assigning sgid permission for group

[root@pc1 ~] # chmod g+s /disk

[root@pc1 disk]# man mkdir

[root@pc1 disk]# info mkdir

[root@pc1 disk]# whatis mkdir

[root@pc1 disk]# mkdir - - help

[root@pc1 disk]# apropos "partition"

Adding user with graphical utility

Show the properties of tony user

[root@pc1 disk]# id tony

Uid=501 (tony) qid=501 (tony) qroup=501 (tony)

Add tow uses john and jhosen with different command with default properties

[root@pc1 disk]# adduser john

[root@pc1 disk]# useradd umer

Assigning password to john

[root@pc1 disk]# passwd john

Add a group

[root@pc1 disk]# groupadd cisco

Customizing users properties at the time of creating user

[-u uid ] [-g primary group] [-G secondary group] [ -c comments] [ -d home directory path ] [-s login shell ]

[root@pc1 disk]# usersadd -u 600 -g cisco -G saad -c "Manager" -d /etc/jonny -d /bin/sh jonny

Modify user properties with usermod command

[root@pc1 disk]# usemod -u 666 -s /bin/bash jonny

Delete a user jonny with his home directory

[root@pc1 disk]# userdel -r jonny

Delete a group cisco

[root@pc1 disk]# qroupdel cisco

All users information stored in /etc/passwd every user have a seven column line in this file

1-user name [ user authenticate at the time of login from the first column of /etc/passwd ]

2-password required [ x means users must required password if remove this x user can login without password]

3-uid [ 500 first user id 0 to 499 id's are reserved 0 for root user and remaining for services users ]

4-gid [ every user relate with any group which stored in /etc/group ]

5-comments [full name but it is not compulsory only for information ]

6-home directory path [ linux file system is read only for normal user only his home directory is with full

permission for normal user

7-login shell (/bin/bash, /bin/sh, /bin/tsh, /sbin/nologin) every user required a shell for login without shell user can never login at machine.

[root@pc1 disk]# gedit /etc/passwd

All groups stored in this file

[root@pc1 disk]# edit /etc/shadow

User password stored in this file

[root@pc1 disk]# gedit /etc/group

For changing directory / to /etc

[root@pc1 /]# cd /etc

One step back /etc to /

[root@pc1 etc]# cd ..

Go to previous working directory

[root@pc1 /]# cd -

Go to current login user home directory

[root@pc1 etc]# cd ~

Show the contents of /etc in single color

[root@pc1 ~]# dir /etc

Show the contents of /etc in different colors with nature of contents

[root@pc1 ~]# Ls /etc

create a folder on root partition

[root@pc1 ~]# mkdir /disk

Create a folder in /disk

[root@pc1 ~]# mkdir /disk/dir

Create multiple folder in multiple directories with single command

[root@pc1 ~]# mkdir /etc/dir1 /var/dir2 /usr/dir3

Create multiple folder in same directory

[root@pc1 ~]# mkdir dir1 dir2 dir3

Copy a file in directory

[root@pc1 disk]# cp file dir

Copy a file from /disk/file and paste it in /disk/dir/

[root@pc1 disk]# cp /disk/file /disk/dir

Copy a directory with –r option

[root@pc1 disk]# cp -r dir dir2

Copy a file from /disk/file and paste it in /etc with myfile name

[root@pc1 disk]# cp /disk/file /etc/myfile

Remove a file

[root@pc1 disk]# rm file

Remove a file with forcefully option

[root@pc1 disk]# rm –f file

Remove a directory with out –r option and you face will an error

[root@pc1 disk]# rm dir

Remove a directory with –r option

[root@pc1 disk]# rm -r /disk

Remove a directory with forcefully option

[root@pc1 disk]# rm -rf dir

Move /etc/dir1 to /disk/ with different name

[root@pc1 disk]# mv /etc/dir1 /disk/mydir

Rename the folder name mydir to dir

[root@pc1 disk]# mv /disk/mydir /disk/dir

Rename the file name with myfile

[root@pc1 disk]# mv file myfile

Read a file page by page with less command

[root@pc1 disk]# less /etc/grub.conf

Read a file page by page with more command

[root@pc1 disk]# more /etc/qrub.conf

Read first ten lines of grub.conf

[root@pc1 disk]# head /etc/grub.conf

Read last ten lings of grub.conf

[root@pc1 disk]# tail /etc/grub.conf

Read first 12 lines with –n option

[root@pc1 disk]# head -n 12 /etc/grub.conf

Read last 11 lines with –n option

[root@pc1 disk]# tail -n 11 /etc/grub.conf

Copy the contents of /etc/grub.conf in /disk/file

[root@pc1 disk]# cat /etc/grub.conf > /disk/file

Append the contents /etc/mtab in /etc/file

[root@pc1 disk]# cat /etc/mtab >> /disk/file

Merging tow commands with pipe sign output of the first command is input of second command

[root@pc1 disk]# cat /etc/squid/squid.conf I more

Count the total lines of squid.conf

[root@pc1 disk]# cat /etc/squid/squid.conf I wc -L

Show only spool words in squid.conf

[root@pc1 disk]# cat /etc/squid/squid.conf I grep spool

Flush the contents of file

[root@pc1 disk]# cat /dev/null > /var/log/messages

/bin All commands which are used by normal users

/etc System conf files

/var Server data logs Mail proxy cache

/dev All devices name stored in /dev

/sbin All commands which are used by supper user

/boot Linux kernel ( vmlinuz , initrd ) Grub directory

/usr All gui tools installed in /usr

/proc System information’s ( picture of RAM )

/home User's home dir's

/tmp Temporary files

/media Auto mounted devices mount point in /media