Do you have a 'nobody' group in your system?

Akhran · 03-13-2006, 07:36 PM

cat /etc/passwd |grep nobody
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh

passwd seems to indicate that user 'nobody' is in group 'nobody'.

However, when I 'cat /etc/group', there isn't any 'nobody' group.

Is that the way it is suppose to be?

Thanks !

dracae · 03-13-2006, 08:03 PM

There should be a nogroup group

ntubski · 03-13-2006, 08:33 PM

Quote:

Originally Posted by Akhran

cat /etc/passwd |grep nobody
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh

passwd seems to indicate that user 'nobody' is in group 'nobody'.
...

Well no actually, that's not what it indicates at all

Quote:

Originally Posted by man 5 passwd

/etc/passwd contains one line for each user account, with seven fields
delimited by colons (":"). These fields are:

· login name

· optional encrypted password

· numerical user ID

· numerical group ID

· user name or comment field

· user home directory

· optional user command interpreter

As you can see none of the fields say the name of the group that a user is in. The second nobody is in the comment/name field.

What /etc/passwd does indicate is that user nobody is in the group with the group ID 65534, which if you go to /etc/group should be the group with the name nogroup.

bc8o8 · 03-13-2006, 09:22 PM

Yes, that is correct and I have the same settings in my /etc/group and /etc/passwd files.

Now I have a question... What is this user/group for? Is it necessary? Since the /etc/shadow file has a * for the password, noone can actually log in as this user (for security I'm sure), so what applications actually use this?

I'm not really asking for any practical purpose, just general curiousity.

lattimro · 08-31-2021, 02:51 PM

Quote:

Originally Posted by bc8o8

Yes, that is correct and I have the same settings in my /etc/group and /etc/passwd files.

Now I have a question... What is this user/group for? Is it necessary? Since the /etc/shadow file has a * for the password, noone can actually log in as this user (for security I'm sure), so what applications actually use this?

I'm not really asking for any practical purpose, just general curiousity.

The nobody user name with user id 65534 was created and reserved for a specific purpose and should be used only for that purpose: as a placeholder for "unmapped" users and user ids in NFS tree exports.

That is, unless user/id mapping is setup for NFS tree exports, all files in the export will appear owned by nobody. The purpose of this is to prevent all users on the importing system from accessing those files (unless they have "other" permissions), as none of them (except root) can be/become nobody.

Therefore it is a very bad idea to use nobody for any other purpose, because its purpose is to be a user name/user id for files that must not be accessible to anybody.