When and why to use Umask ?

tofee · 03-24-2006, 01:56 AM

hi,

When i have to use umask and why ? pls make me understand clearly. i am confused with the concept.Umask concept is not clear to me.

thanx..

mbreith · 03-24-2006, 02:02 AM

To understand umask, you will have to understand file permissions. www.google.com/linux search for file permissions.

umask is a way of rejecting permissions. Even if you tell the system to give full permissions, it will mask out those permissions in the umask, and will not grant them. The only place I have run into this is when setting up an fstab entry for a windows partition. It usually umask's write access.

Tinkster · 03-24-2006, 02:27 AM

Sorry, but there's a bit of a misconception happening here.

umask is NOT about rejecting any permissions. It is used
to define the default mode of a newly created file, and the
perms are XORed. E.g., a umask 022 will create a file with
644 permissions for you when you save a new file from an
editor.

The usage of umask in mount-entries in fstab is a whole
different story, read

Code:

man mount

and

Code:

man bash
/umask 
(press n a couple of times)

for details

Cheers,
Tink

praveen_b744 · 11-26-2009, 04:50 AM

HI,

1) In breif: Maximum permissions - UMASK value = Default permissions.
2) For Executables (Exg: directories) total permissions = 777
For text files ( Normal files ) total permissons = 666
Lets say Umask value is 022, then Default permissions of a directory is 755 (777-022=755).

malekmustaq · 11-26-2009, 10:21 AM

tofee,

as a young linux user please do not play with 'umask'. Every linux generally defaults to umask of '0022' and that is the only acceptable default if you are concerned of security. Every file you (username) have created bears automatically the proper safe permissions based on your 0022 default umask. There are only exceptional instances that the user has to manipulate the mask. And that instance should not occur at a time that we are still young. :-)

Click this link, it has a short but good explanation about permissions and it has a good say about 'umask'.

Hope this helps.

Goodluck.