« Previous Next »

LINUX PERMISSIONS

Linux Standard File Permissions 


            Read     r    Read the file contents
            Write    w    Write and modify contents
            Execute  x    Execute the file if it is program file
                         If it is directory user can cd to the directory

Permission groups 


            1) Owners – for individual
            2) Group owners – for group members
            3) All others users – for those users who are not owner and not in
                       ---    ---     ----
                       rwx    rwx     rwx
                       user   group   others
                       Check permissions using
                       #ls –l

Change ownership of files 


#chown <who> <what>
#chown user1 imax
#chown –R user1 Dir1

Change group ownership of files 


#chgrp <group> <files>
#chgrp cisco datafile1.txt


Examples:
#groupadd Engg
#chgrp Engg file1.txt file2.txt
#chgrp –R Engg Dir1

Change permissions using Symbolic mode 


                                    
#chmod <options> <permissions> <file name>
-R It stands for recursive
-V It stands for verbose
#chmod u+x filename
#chmod u+r,g+x filename
#chmod u-rx filename
#chmod a+x filename
#chmod u=rw,go=rw Demo.txt
#chmod o+w *.txt

Set write permission to user with Symbolic mode 


#chmod u+w filename
#chmod u+w demofile1.txt

Change permission with numerical method


When we represent Linux permissions using numbers, it is called as
numeric mode. In numeric mode three digit value represents specific file
permissions like 777 , and these values are called as octal values.
First digit is for owner permission, second for group permission and third for
other users permission.
4 stands for "read",
2 stands for "write",
1 stands for "execute"
0 stands for "no permission"
Example
755
Owner : rwx = 4+2+1 = 7
Group : r-x = 4 + 1 = 5
Others: r-x = 4 + 1 = 5
Examples:

                                    
#chmod 777 filename
#chmod 755 filename
#chmod 644 filename
#chmod 750 filename

Set all permission to user only with Numerical mode 


#chmod 700 filename

Set write permissions to group 


#chmod g+w groupname
#chmod g+w userlist.txt

Remove permissions on files for others 


#chmod o-rwx filename
#chmod o-rwx demofile

Find result of permissions 


#ls -l
« Previous Next »