I'm new to Linux administration, doubly so for servers. I've noticed that by default Linux (in my case Debian 5.0) installs a whole bunch of default users, which I assume is to manage their own individual processes without a security risks to other programs.

Is it a good or bad idea to remove some of these users? As a beginner I'm not sure which are needed, but at the least for a remote server I don't why I'd need a user for games or for the print daemon.

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David Shaw, a.k.a. "Trazoi"

These users exist because a package installed on the server said it needed them. Whether any particular one will actually end up being used depends on what you do with the system, but just yanking things out that the OS put there itself is a very bad idea. Think about the tech support horror stories you hear about people who started deleting all those "extra" files they "never use" and wound up trashing their system.

And there's really no reason to remove them. They consume no resources beyond the few bytes they occupy in the passwd and related files, and they can't be logged into (unless you decide to enable them and set a password for them -- don't do that), so there's no security risk.

Sweet, thanks. I wasn't sure if they had full user rights, passwords and all. If they're there effectively just as labels to quarantine file access then I won't worry about them. I was just a little bit surprised there were so many of them.

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David Shaw, a.k.a. "Trazoi"

You can verify that none of them have passwords by looking at the second field in /etc/shadow.

A "valid result of crypt" looks something like $1$EPlC0/$zcsNziSht7Vt335LyraXZ/. Also you will often see in /etc/passwd such accounts having their shell set to /bin/false or /sbin/nologin which prevents a normal login. It is still possible (and common) for processes to run as these users. For example, postfix starts as root (it needs to in order to e.g. listen on port 25) but then drops most privileges and switches over to the postfix user. I don't know exactly what would happen if you removed the postfix user account, but I assume it isn't good...

Ah, interesting, thank you.

Now I'm curious as to what the difference is between having a ! or a * as the password. The shadow man page doesn't say, and I'm sure that's a devil of a thing to try and Google for!

Pre-edit: Decided to search on a whim before pressing submit, and found out that * means nothing can match, while ! means the account is locked.

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David Shaw, a.k.a. "Trazoi"