How to pass a password in bash script?

Question

I need to execute a command which is needed to run as root.

I read some post about using hard-coded passwords in scripts could be insecure, but actually I don't care because I'm providing root password to users anyway. It's an stripped system and there's only 2 users: client and root, so avoid warning me about security issues, Go ahead and give a quick and dirty solution.

For this bash script I need to get as superuser using su, then "my command", and then logout.

I don't want the terminal prompt to type the password myself, instead read the password that I'm providing somewhere in script and run the command. It's a priority to not prompt any input by user.

Alternatively, maybe I could install sudo, but is there any chance to run a command without any prompt of password (editing sudoers or something)? What about of using expect?

Update: I forgot to say that is also a portable SO, used for USB sticks (maybe later for CDLive too), as you know, in some distros of this kind is provided a root password if users needed. The command mentioned before is a package extensions for some application install, and only root have privilegies to execute such command (I have to say it's not a apt-get install or rpm command, so don't worry about this).

You may get a better answer by describing what you need the script to actually do. Bypassing UNIX's access control infrastructure like that is the UNIX equivalent of a GOTO statement: if you're tempted to use one, it usually means it's time to step back from the problem for a bit and see if you can do what you're trying to do more elegantly. — Ori
– Ori, Commented Mar 7, 2011 at 3:55

Charles Duffy · Accepted Answer · 2011-03-07 03:57:29Z

If you want a command to be runnable with no password, set that specific command as runnable with no password in your /etc/sudoers file (limiting the arguments to only the specific ones you wish to allow, if your use case allows that limitation).

This is as simple as setting the NOPASSWD: flag for the relevant sudoers entry.

If you really, really don't care about security, it could be as simple as this:

%admin ALL=(ALL) NOPASSWD: ALL

(after putting sudo-capable users in the admin UNIX group)

...or, if you did care, you could do something specific:

someuser ALL = NOPASSWD: /usr/local/sbin/my_admin_command

Note that if these commands will be run with no user present, they also may not have a TTY assigned; in such a case, you must be sure that your sudoers file doesn't contain the (oft-present-by-default) line:

Defaults requiretty

...or that the effect of this default is being specifically discarded by the line granting permissions.

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