Chmod

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Contents 1 chmod - change permissions on files 1.1 To see the current permissions on files and directories (folders): 1.2 The format of permissions are: 1.3 Common Permissions are: 1.4 Make a Sticky Directory or File

chmod - change permissions on files

Note: This is only a Basic guide to chmod, covering some niche areas.

To see the current permissions on files and directories (folders):

sburke@server:~$ ls -la

-rwx---r-x   1 sburke users    1834 2006-09-07 17:48 .bashrc
drwxr-xr-x   2 sburke users    4096 2006-10-21 17:08 public_html
-rw-r--r--   1 sburke users      73 2006-09-28 12:03 .screenrc

The format of permissions are:

-------user---------- ------group---------- ------world---------
read, write, execute, read, write, execute, read, write, execute

Common Permissions are:

chmod 000  //removes 
chmod 400  //read permission to the user
chmod 500  //read & execute permission to the user
chmod 600  //read & write permission to the user
chmod 700  //read & write & execute permission to the user.

So - mixing and matching the above numbers can give:

chmod 644  //gives read&write to user, AND gives read to group and world.
chmod 755  //gives read&write&execute to user, AND read&execute to group and world.

Make a Sticky Directory or File

A sticky file means that you can allow people to read and write to the file, however they cannot remove/delete the file. Similarly with a sticky directory: people can read, write and execute a directory and its contents, however they cannot remove the directory.

chmod +t file
chmod +t directory
ls -la
drwxrwxrwt

The /var/tmp has the sticky permission - so people can write inside the tmp directory, but they cannot remove the directory itself.

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More info:

http://www-128.ibm.com/developerworks/aix/library/au-speakingunix4/?ca=dgr-lnxw07UNIXpart4