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On Ubuntu, in what kind of situations, if any, running a command as a non-root to access a file/folder or create/delete a file/folder using sudo may result in "permission denied" while running the same command as root user would succeed? The user is assumed to be a sudoer, of course.

Practical example on Ubuntu 12: I've got this directory in / with root:root ownership and drwxr-xr-x permissions and I tried sudo date > file while in it as well as sudo date | tee file but got the same

-bash: file: Permission denied

in both cases. Sure enough, there're no problems if I'm root. This is quite frustrating.

Evandro Silva
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Desmond Hume
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  • Yes, it would succeed. – Hckr Nov 13 '12 at 22:59
  • Running commands on a file without sudo depends on the permissions of the file, whether you're an owner of that file, belong to a group that has permissions for that file, etc. It also depends on what you're doing with it such as viewing, modifying, moving, deleting, running, etc. To see the permissions of a file you have access to in Nautilus, right click it and select Properties, then the Permissions tab. To read about file permissions, see http://askubuntu.com/questions/83/how-do-file-permissions-work. – James Nov 13 '12 at 23:09
  • Does the file to which you pipe have the immutable bit set? See https://secure.wikimedia.org/wikipedia/en/wiki/Chattr – 0xC0000022L Nov 14 '12 at 00:17

2 Answers2

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What's the command you are trying? A common mistake is sudo foo > output which doesn't run the output redirection as root because it's done by the shell. A solution to this one would be foo | sudo tee output (or sudo foo | sudo tee output if foo requires root access)

Dennis Kaarsemaker
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sudo lets you run a program as another user - as root by default.

It's the same as if root runs that program (except maybe for some environment variables and such). So there is no such situation.

Florian Diesch
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