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#1 2010-02-02 19:46:24

Giacomo Ritucci
Member
From: Bologna, Italy
Registered: 2009-10-25
Posts: 26

Problems with system account

I needed an user for mldonkey and I issued the following command:

sudo useradd -b /shared -m -U -s /bin/false -r p2p

in order to create the p2p system account (-r) with the same named group (-U), the /shared/p2p home directory (-m -b /shared) and no login shell (-s /bin/false).

Something has gone wrong because the p2p group has been created with the same gid of the nobody group:

$ grep 'nobody\|p2p' /etc/group
nobody:x:99:
p2p:x:99:

the p2p user belongs to the nobody group:

$ groups p2p
nobody

and I can't delete the p2p group or even modify its gid:

$ sudo groupdel p2p
groupdel: cannot remove the primary group of user 'nobody'
$ sudo groupmod -g 124 p2p
groupmod: Cannot determine your user name.

(the groupmod error message doesn't make any sense to me)

Any ideas?


One of these days I'm gonna learn to play and write myself a song

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#2 2010-02-02 20:59:28

ruffedgz
Member
From: Michigan
Registered: 2009-07-23
Posts: 54

Re: Problems with system account

This isn't best practice but what if you manually change the group id of 'p2p' in /etc/group and also change the group id for the user 'p2p in /etc/passwd (if you go this route, pick a number in the thousands like 2000 or something)?

This isn't something you want to do all the time but I don't see this being done with any user or group command.

Like I said, this isn't good practice but if you exhausted your options with using the 'usermod' 'userdel', 'groupmod' and 'groupdel', then you don't have to many other options...

Just a thought.


Arch linux i686 | Dell XPS m1530 | Intel Core 2 Duo 2 GHz | 3 GB RAM | 250GB HDD

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#3 2010-02-02 22:52:13

Giacomo Ritucci
Member
From: Bologna, Italy
Registered: 2009-10-25
Posts: 26

Re: Problems with system account

Thanks ruffedgz, but just to be sure I restored the /etc/passwd- /etc/group- /etc/shadow- backups.

I tried

groupadd -r p2p

but gid was 99, same as `nobody' again.

So I guess the cause of the problem is groupadd selecting a gid that's already used.

Am I the only one with this issue?


One of these days I'm gonna learn to play and write myself a song

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#4 2010-02-03 08:58:54

EVRAMP
Member
From: Czech Republic
Registered: 2008-10-03
Posts: 173
Website

Re: Problems with system account

I think the group must exist before adding user into it. You may try to use groupadd to do that. If it complains try, deleting the p2p group first.

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#5 2010-02-03 23:39:31

ruffedgz
Member
From: Michigan
Registered: 2009-07-23
Posts: 54

Re: Problems with system account

So I tried your command on post #3 and got the same thing. The reason for that is I never set my SYS_GID_MIN and SYS_GID_MAX in the /etc/login.defs file. Use whatever editing software you like and add this line to the bottom of the file:

SYS_GID_MIN 1 #can't use 0 since that is root
SYS_GID_MAX 99

Save the file. Perform the command:

groupadd -r p2p

and the group will use a number that is between the min and max for system groups. Hope this works for ya.


Arch linux i686 | Dell XPS m1530 | Intel Core 2 Duo 2 GHz | 3 GB RAM | 250GB HDD

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#6 2010-02-04 19:38:11

Giacomo Ritucci
Member
From: Bologna, Italy
Registered: 2009-10-25
Posts: 26

Re: Problems with system account

Thanks ruffedgz.

It's a shadow bug:
http://bugs.archlinux.org/index.php?do= … k_id=16092

From the bug tracker's comments it seems that there's no obvious solution.

I prefer not to fiddle with logins.defs, so I think I will use user accounts also for services like mldonkey until this bug is fixed.


One of these days I'm gonna learn to play and write myself a song

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