HowTo: Create a Passwordless / Guest Login (Simple Method)

[aysiu]

Yes, I realize such a HowTo already exists (HowTo: enable passwordless logins via GDM), but this method is entirely different and, I think, less complicated.

Warning: Even though this method is simple (few steps), it is extremely dangerous if you don't know what you're doing. Do not attempt this if you are worried that you might mess up the /etc/shadow file, thus screwing up your Ubuntu system, possibly irreparably!

This is an oft-requested task, mainly for people who don't want to require less tech-savvy family members to have to remember passwords. It is a security risk, but I think people should at least know how to put their computers at risk if they want to. Don't blame me if anything bad happens.

Step 1
Make sure you have created a user. For the sake of this example, let's say you called the account username guest. You can give it any temporary password you want. We're going to change that password shortly anyway. I'm assuming you know how to do this already. If you don't, I can assure you that this HowTo is not one you should be following, and you would be very likely to screw up the next step.

Step 2
Next, go to the terminal and paste in this command:

sudo nano -B /etc/shadow

This will open the /etc/shadow file (the one that contains all the passwords) in a text editor called Nano.

Once you have it open, find the appropriate line for the account in question. It'll look something like this:

guest:$1$2TUdk8Z0$tb2Fn6Idgo8dq9EgYv4xZ0:13721:0:99999:7:::

Change the second part (in bold here) to match this second part (also in bold):

guest:U6aMy0wojraho:13721:0:99999:7:::

Then save the file (Control-X, Y, Enter).

Now you should be able to log into the guest (or whatever you called it) account without entering a password.

[wieman01]

Nice one, Aysiu!

[aimran]

Would this give the guest sudo access at the terminal?

[wieman01]

Would this give the guest sudo access at the terminal?

If you give the guest account administrative rights, yes. Otherwise it shouldn't.

[Frak]

Great job Aysiu! Very helpful.

[aysiu]

Would this give the guest sudo access at the terminal?

No. This has nothing to do with user privilege. It has only to do with the user password being blank.

If you want to add your guest user to the admin group, then that's a separate step, and one I would strongly advise against.

[andrewsomething]

@Aysiu

Worked like a charm. Would you mind explaining a little more? I assume "U6aMy0wojraho" is the encryption for nothing?

[aysiu]

@Aysiu

Worked like a charm. Would you mind explaining a little more? I assume "U6aMy0wojraho" is the encryption for nothing?

I would assume the same thing. More details on how I figured this out:
http://ubuntucat.wordpress.com/2007/...unt-in-ubuntu/

[Frak]

Didn't think about looking at that, aysiu. Good thinking
Pretty clever.

[andrewsomething]

@Aysiu

So I looked at the /etc/shadow file, which holds encrypted passwords for all users, on the live CD and found that the encrypted password for the user ubuntu is U6aMy0wojraho. So I tried editing the /etc/shadow file on my own installation of Ubuntu and changing the password for a test user from its previous encrypted password to U6aMy0wojraho, and I was able to log in as that user without entering a password.

Cool!

Thanks for mucking around your with system to figure that out....