Chrome Version: 60.0.3112.114 (Official Build) (64-bit)
Chrome OS Version: 9592.96.0 (Official Build) stable-channel auron_yuna
Chrome OS Platform: Acer CB5-571
Network info: NA

Please specify Cr-* of the system to which this bug/feature applies (add
the label below).
Unknown

Steps To Reproduce:
As root user, attempt to add a group 'rkt':

localhost ~ # groupadd rkt
groupadd: cannot lock /etc/group; try again later.

I'm running as root.
localhost ~ # id
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),26(tape),27(video),207(tss),208(pkcs11),219(wpa),1001(chronos-access) context=u:r:chromeos:s0

There aren't any /etc/group.lock files or any lock files in /etc/.
localhost ~ # ls -l /etc/group*
-rw-r--r--. 1 root root 1734 Sep 16 14:28 /etc/group
localhost ~ # ls -l /etc/*lock
ls: cannot access '/etc/*lock': No such file or directory

System information:
localhost ~ # uname -a
Linux localhost 3.14.0 #1 SMP PREEMPT Sat Sep 16 09:53:16 PDT 2017 x86_64 Intel(R) Celeron(R) CPU 3215U @ 1.70GHz GenuineIntel GNU/Linux

localhost ~ # cat /etc/os-release
BUILD_ID=9592.96.0
NAME=Chrome OS
ID_LIKE=chromiumos
GOOGLE_CRASH_ID=ChromeOS
VERSION_ID=60
BUG_REPORT_URL=https://crbug.com/new
VERSION=60
HOME_URL=https://www.chromium.org/chromium-os
ID=chromeos


As non-root user with sudo:

chronos@localhost ~ $ sudo groupadd rkt
Password: 
groupadd: cannot lock /etc/group; try again later.
chronos@localhost ~ $ id
uid=1000(chronos) gid=1000(chronos) groups=1000(chronos),7(lp),18(audio),27(video),208(pkcs11),222(input),240(brltty),403(devbroker-access),600(cras),601(wayland),602(arc-bridge),1001(chronos-access) context=u:r:

Expected Result:
rkt group should be added

Actual Result:
Exception thrown and no group added.

How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)
Always - tried restart and problem persists

What is the impact to the user, and is there a workaround? If so, what is
it?
None at this time

Please provide any additional information below. Attach a screen shot or
log if possible.
When running the command with sudo I see the below in /var/log/secure:

2017-10-02T20:09:34.939216-04:00 NOTICE sudo[9358]:  chronos : TTY=pts/0 ; PWD=/home/chronos/user ; USER=root ; ENV=LD_LIBRARY_PATH=/usr/local/lib64 ; COMMAND=/usr/sbin/groupadd rkt
2017-10-02T20:09:34.940896-04:00 INFO sudo[9358]: pam_unix(sudo:session): session opened for user root by (uid=0)
2017-10-02T20:09:34.943722-04:00 INFO sudo[9358]: pam_unix(sudo:session): session closed for user root


======

This may not be a bug, but I wasn't able to find a way to create a new group.  Is this expected behavior where Chrome OS doesn't allow you to create a group.  Please excuse me if so - I'm a novice in terms of Chrome OS.

This whole exercise is an attempt to run rkt container engine as I'd prefer not to have to build a custom kernel to run docker engine.

Reference doc: https://coreos.com/rkt/docs/latest/trying-out-rkt.html