Why is sudo bash needed?

I was reading the following code:

$ sudo bash # cd /home/ # ./gitpull.sh 

Why do I need the first line, what does it do exactly? What if I just did $ sudo instead of $ sudo bash ?

6 Answers

It starts a bash shell as a root level user. You need it because typically normal users can't access /home/

The danger of what you are doing is you are in a root shell -- you can mess up your machine rather easily.

You would be much better off doing:

$ sudo sh -c 'cd /home; ./gitpull.sh' 

Because the commands invoked as root will be logged. Invoking a shell directly through sudo avoids all of the security benefits of sudo and should be avoided.

sudo <shell>, if it works, betrays a poor installation of sudo and a potential security weakness.

sudo should not be configured to allow arbitrary commands like shell; the purpose of sudo is to allow authenticated non-root users to run certain commands as root, without knowing the root password.

If sudo bash is allowed to any user, that user is root simply by virtue of knowing his own password.

If an attacker obtains the password of any one of the accounts which are able to do sudo bash, the attacker thereby has root.

The proper way to do the equivalent of sudo bash (obtain a root shell) is su, followed by giving the root password, not your own.

The infamous sudo is an acronym of sorts for Superuser Do.

It basically make a normal user a Super user for a short while.

In your command sudo bash , effectively you are saying Superuser do --> a Bourne shell ( bash ) Which opens a root user logged in shell.

If you just ran sudo the operating system wouldn't know what to do. So in general sudo is followed by a unix command.

sudo allows users to run programs with the security privileges of another user (normally the superuser, or root).
bash starts a new bash shell.
So, sudo bash starts a new bash shell with the security privilege of root user.

I'm betting sudo bash instead of sudo is specified to

• absolutely ensure you are invoking ./gitpull.sh from bash and not another shell such as tcsh, pdksh or plain old sh. I'm pretty sure the script's hashbang line should allow the script to specify what shell to run it under but maybe it was omitted for some reason or the instruction writer doesn't want you to rely on that.
• I believe if you start bash without other arguments it doesn't act like a "login shell" and maybe the script depends on that.
• a force of habit from the person who wrote the instructions (maybe he/she works in a multi-shell environment).
• perhaps the instruction writer is not very skillful or has bad habits from other environments.

Also @nisdis is right. Plain old sudo just prints usage information. But why not use su...