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linuxshellsudosu

su and sudo in a shell script

There is a shell script (/bin/sh, not bash) that requires root permissions for execution.

If it is ran by a normal user it should ask user a password to get root access and re-run itself.

Now it uses the following code:

if [ $(id -u) -ne 0 ]; then su root -- $0 $@ ; ... fi

That works fine, but there are some OS like Ubuntu that has no root password at all. On the other hand, a lot of systems use sudo for root permissions.

The question is: how can the script detect whether to use su or sudo without asking the user to enter too much passwords (e.g. enter sudo password, if it fails - run su).

Solution

  • There isn't a bullet-proof way of doing this, because any distribution can lay files in any way it wants. Debian and Ubuntu often place system files in directories other than Red Hat, for example. It's much easier to customize the script for the OS it's installed on.