Linux – Why can’t MongoDB create users when installing Ubuntu 11.10?

I’m installing MongoDB on my Ubuntu 11.10 machine. Add the appropriate line to /etc/apt/sources.list (using instructions from here), I enter the following to install:

sudo apt-get install mongodb-10gen

The results are as follows:

Adding system user `mongodb' (UID 117) ...
Adding new user `mongodb' (UID 117) with group `nogroup' ...
useradd: cannot lock /etc/passwd; try again later.
adduser: `/usr/sbin/useradd -d /home/mongodb -g nogroup -s /bin/false -u 117 mongodb' returned error code 1. Exiting.
dpkg: error processing mongodb-10gen (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 mongodb-10gen
E: Sub-process /usr/bin/dpkg returned an error code (1)

I only opened other terminal windows (none of them ran any programs) and Chromium. Why might the installation fail to add users?

Thanks,

ParagonRG

Solution, thanks to ‘Thomas’, comes from this resource :

Find /etc/group.lock, /etc/

passwd.lock, and /etc/shadow.lock and delete them. Make sure you only delete these files if they exist.

Once this is done, I can simply rerun the install command and it will complete successfully.