Comments on: Linux permissions demystified

By: Swivel

Swivel — Fri, 02 Dec 2016 07:19:57 +0000

Spelling error...

Getting sticky! There are three special permissions: SetUID, SetGID and Stciky. They have different meanings when used on normal files compared to directories.

"Sticky" is spelt "Stciky" in the blog post (see snippet above)

By: Scott

Scott — Mon, 20 Oct 2014 20:45:54 +0000

This is wrong. A hard link is a second directory entry that points to the same inode. Since all file metadata other than the name (including owner, group, mode (permissions number), and ACL) are in the inode, this means that a file and a hard link to that file cannot have different owners or groups.

By: Mike B

Mike B — Thu, 17 Nov 2011 23:36:31 +0000

Nit:

-rw-rw---- 1 matt users 0 2011-04-21 10:28 finaltest.txt

Should be:

-rw-rw---- 1 matt users 0 2011-04-21 10:28 finaltext.txt

Good stuff

By: Prashant

Prashant — Wed, 21 Sep 2011 05:50:15 +0000

thank u sir, I got much useful information from you.

By: Matt Jenkins

Matt Jenkins — Tue, 26 Apr 2011 09:16:21 +0000

@warren agreed, but ACLs aren't always available. This is meant to be a generic method that is available whether you are on Linux, BSD, SCO, AIX, Solaris ...

By: warren

warren — Mon, 25 Apr 2011 12:46:33 +0000

@Matt - while an interesting solution, that also means every group needs to recall the name of their file to make edits .. seems like a lot more complicated than using ACLs.

By: Matt Jenkins

Matt Jenkins — Sat, 23 Apr 2011 22:24:28 +0000

@warren - the only extra piece of knowledge you'd need for the second question is that if you want to specify multiple sets of attributes you will have to do it on separate hard-links to the file. Those can be created with the 'ln' command (ln myfile myfilelink). Then you can allow 1 group to have read access on "myfile" and 1 group to have write access on "myfilelink". Both files reference the same data, so changing one file will also change the other.

Unix file permissions does seem to be a commonly asked question all over the place - hence we decided to write an article about it.

By: warren

warren — Fri, 22 Apr 2011 13:17:36 +0000

This is a great write-up of the basic *nix permissions model. But it does not address at all the second sample question (http://superuser.com/questions/161204/linux-file-permissions).

There are at least a couple questions on ServerFault that address this topic as well: http://serverfault.com/questions/84373/how-granular-is-too-granular-with-file-permissions & http://serverfault.com/questions/84370/what-filesystem-comes-closest-to-matching-ntfs-for-support-of-acls-and-highly-gr