LINUX CLASSES - FILES

How Can I Change Linux File Permissions?

Using Chmod to Change a File's Permissions

Fine; you can decipher the permissions for a file or directory, but what if you want to change them? Maybe you've decided that the pig_info file is a little too sensitive for just anybody to view, or that you should allow all users to execute the zippity program. The chmod (change mode) command can take care of that.

The general form of the chmod command is

chmod <permission flags> <file or directory name(s)>

To tell chmod the new permissions for a file, you can use any combination of these permission flag characters:

WHO IT APPLIES TO	ACCESS CHANGE	ACCESS TYPE
(pick one or more)	(pick one)	(pick one or more)
u For the owner	+ Grant access	r For read access
g For the group	- Deny access	w For write access
o For all others		x For execute access

Here are some examples:

chmod o-r pig_info Remove read access from all others.

chmod g+rw pig_info Grant read and write access to group.

chmod ugo+x zippity Grant execute access to everybody.

In effect, you're saying "change the mode for these people by adding/removing their access to read/write/execute the file named whatever." Just pick the proper combination of flags in each of the three columns, depending on what type of access you want for the file.

Note: If you give chmod a directory name instead of a file name, the permissions have slightly different meanings. For a directory, read access means that you can list the files with the ls command; write access allows you to create or delete files; and execute access gives you the ability to change to that directory with the cd command.

Transferring Ownership of a File Using Chown

If you are logged in as root, you can transfer ownership of a file or directory (if you move it into another user's directory) using the chown command.

To tell chown what to do, just give it the new owner and the file name, like this:

chown sigmund zippity

This will make sigmund the owner of zippity. Once you've transferred ownership, sigmund will be able to set the file's permissions (with chmod) if he wants to.

For more information on the chmod command, see the chmod manual.

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Comments (most recent first)

dood (30 Jul 2010, 13:44)

btw, sorry about bad grammer ,I copied some parts of it from someone else's post and forgot to change them.

dood (30 Jul 2010, 13:39)

Hi,i'm try to change primission of one my hard drives, but the "chmod" doesnt change anything.
this is result of ls -l before chmod 777 /media/win :
debian:~# ls -l /media
dr-x------ 1 root root 12288 2010-07-30 04:33 win

and the result after doing chmod :
dr-x------ 1 root root 12288 2010-07-30 04:33 win

this win folder is a ntfs (my windows vista drive)
that i can access it as root ,but other users cant access it.
i've changed the fstab and the owner so other users have the rights to use it but still i cant see the contents of it but still doesn't work.
do you have any idea why i cant access this folder as an user?thanks
kourosh

Cristian Kleuser (20 May 2010, 19:31)

Hi, I'm trying to set a folder, the right permission to all my users read and write content on them (creating and editing files and sub-folders) but I don't know how to set that... How can I do this ? Do I have to create all the users to the same group? how to set groups autorization etc? thanks

Bob Rankin (17 Feb 2010, 22:54)

Yes. Those 755's and 644's are a tad geeky, dontcha think?

ralphaw (17 Feb 2010, 11:16)

Did you opt not to include the command with octal changes, so as not to have to explain BCD(binary coded decimal)?


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