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I know root has very strong permissions in Unix, but I was wondering if it can circumvent the file permission system.

I have a directory whose owner is not root, the directory has permissions drwxr-xr-x. I know that the root user can delete files in this folder also after doing chown, chmod or something similar.

Can a root user also delete these files without doing any sort of chwon, chmod etc. (for example rm -f). Assume files itself have all permissions. I my opinion it should not be possible. This is an important production problem.

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Yes, root can delete any file regardless of its permissions. Anyone who can't be trusted with that privilege should not be given root access.

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Thanks for answering. Can the root user delete the files in the scenarion I mentioned without using chgown (change owner), chmod (or something similar). As you know file permssions is irrelevant, what is relevant is directory permission. – Jim Dec 20 '11 at 16:23
To rephrase: Using the sceario I asked, assume the directory is mydir and file is myfile. Myfile has rwxrwxrwx, not owned by root. mydir has rwxr-xr-x and not owned by root. We have script which is owned by root and is run. The scripts tries to remove myfile with rm -f myfie. Two cases are possible with script: a) Do a chmod 777 mydir and then rm -f file and then chmod 755 mydir. b) just try rm-f myfile without any other steps. Wwill option b also work?? – Jim Dec 20 '11 at 16:29
@Jim: To slightly rephrase what Mike said, root can delete any file regardless of any permissions. – grawity Dec 20 '11 at 16:46
Thanks grawity I get it. :-) I know I tend to be verbose. The question background. We have directories mydir and mydir/onemoredir in production whih belong to a non-root user. mydir has rwxr-xr-x and onemoredir has rwxrwxrwx. There is a script which runs a root. It is able to delete all files in onemoredir, but not in mydir. Thanks Jim – Jim Dec 20 '11 at 16:56
Please edit your question to provide uname -a – kubanczyk Dec 20 '11 at 19:14

On traditional Unix systems that use discretionary access control (DAC) root can indeed delete any file with no regard to permissions. One exception that comes to mind is NFS-mounted directory (hosted on remote server), depending on exportfs root= option.

On modern mandatory access control (MAC) Unix-like systems, such as SELinux, root may be stripped of such special capability.

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