'lineinfile' module - possible bug?

[Willard Dennis]

Hi all,

I have a playbook used for setting up new servers here, that among other things, ensures both NTP and NIS (yes, we still use NIS here...) are installed and are running. The problem I am seeing is that when the playbook executes the notify action for restarting the ntpd service, it is failing because the 'ntp' user is no longer in /etc/passwd. I believe the problem is occurring when I run tasks in the playbook that call the 'lineinfile' module to ensure I have a certain entry needed for NIS logins at the bottom of /etc/passwd, which seems to be overwriting the then-last-line which is the 'ntp' user one.

Here is the tasks that make sure NTPD is installed and running...

[...]

- name: DEBFAM | Ensure NTP package is installed
apt: pkg=ntp state=present
tags: ntp

- name: DEBFAM | Ensure NTP configured correctly
template: src=ntp.conf.j2 dest=/etc/ntp.conf
notify:
- restart deb-ntpd
tags: ntp

- name: DEBFAM | Ensure NTP is running and enabled
service: name=ntp state=running enabled=yes
tags: ntp

[...]

Right after these steps are run, I can cat /etc/password and notice that the 'ntp' user entry is there, and happens to be the last entry...

[...]
rtkit:x:116:124:RealtimeKit,,,:/proc:/bin/false
saned:x:117:125::/home/saned:/bin/false
whoopsie:x:118:126::/nonexistent:/bin/false
speech-dispatcher:x:119:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/sh
hplip:x:120:7:HPLIP system user,,,:/var/run/hplip:/bin/false
ntp:x:121:127::/home/ntp:/bin/false

Then the playbook runs the tasks I have set up to ensure NIS is installed and running...

[...]

- name: DEBFAM | Ensure NIS package is installed
apt: pkg=nis
tags: nis

- name: DEBFAM | Ensure /etc/yp.conf configured correctly for NIS
template: src=yp.conf.j2 dest=/etc/yp.conf
notify:
- restart nis
tags: nis

- name: DEBFAM | Ensure /etc/defaultdomain configured correctly for NIS
template: src=etc-defaultdomain.j2 dest=/etc/defaultdomain
notify:
- restart nis
tags: nis

- name: DEBFAM | Ensure /etc/nsswitch.conf configured correctly for NIS
template: src=nsswitch.conf.j2 dest=/etc/nsswitch.conf
tags: nis

- name: DEBFAM | Erase old /etc/passwd entry for NIS users
lineinfile: dest=/etc/passwd
regexp='::::::+'
state=absent
tags: nis

- name: DEBFAM | Erase old /etc/shadow entry for NIS users
lineinfile: dest=/etc/shadow
regexp='::::::::+'
state=absent
tags: nis

- name: DEBFAM | Ensure NIS is running and enabled
service: name=ypbind state=restarted enabled=yes
notify:
- restart autofs
tags: nis

- name: DEBFAM | Ensure /etc/passwd has correct entry for NIS users
lineinfile: dest=/etc/passwd
regexp=''
insertafter=EOF
line='::::::+'
notify:
- restart nis
tags: nis

- name: DEBFAM | Ensure /etc/shadow has correct entry for NIS users
lineinfile: dest=/etc/shadow
regexp=''
insertafter=EOF
line='::::::::+'
notify:
- restart nis
tags: nis

[...]

(I'm running the lineinfile module once on /etc/passwd and /etc/shadow to remove any old existing entries for the '+::::...' patterns, and then running them again on those files to ensure they are present and at the end of those respective files.)

However, when the playbook is ending and running the accumulated notifies, when it hits the 'restart deb-ntpd' action, this fails, complaining that the 'ntp' user is not there --

NOTIFIED: [common | restart deb-ntpd] *****************************************
failed: [dhcp-207-150] => {"failed": true}
msg: * Stopping NTP server ntpd
...done.
* Starting NTP server ntpd
* user "ntp" does not exist


FATAL: all hosts have already failed -- aborting

If I then cat /etc/passwd, I notice that the entry for the 'ntp' user is gone, and seemingly overwritten by the NIS entry:

[...]
rtkit:x:116:124:RealtimeKit,,,:/proc:/bin/false
saned:x:117:125::/home/saned:/bin/false
whoopsie:x:118:126::/nonexistent:/bin/false
speech-dispatcher:x:119:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/sh
hplip:x:120:7:HPLIP system user,,,:/var/run/hplip:/bin/false
::::::+

This has happened a number of times to me, enough that I believe I'm hitting a bug (or am using the 'lineinfile' module incorrectly somehow??) so I thought I'd post it to this list and ask for help with debugging this....

Thanks,
Will

[Michael DeHaan]

lineinfile is tricky and I don't have bandwidth to debug this one right now, but maybe some other folks would like to help?

Most of the time, I *strongly* recommend just templating the file, that way you are centrally very sure of the state of everything that's in there.

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[James Cammarata]

Also, is there any reason you're not using the user module to manage entries in your passwd/shadow files?

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[Willard Dennis]

Sorry, other work took me away from pursuing this issue until now... Thanks for your attention, Michael & James!

In any case, it seems the entry I need is actually "+::::::" in /etc/passwd, per this webpage: http://www.linux-nis.org/nis-howto/HOWTO/settingup_client.html (and not "::::::+" as I've been using, which is weird, because NIS logins are working with that... but I digress...)

I can't really template the /etc/passwd and /etc/shadow files, as the users can install software that enters new users that my Ansible playbooks wouldn't know about... And I'm pretty sure I can't use the "user" module; I don't want to create an actual local user (and homedir etc.), just add the literal line "+::::::" at the bottom of /etc/passwd to create the needed entry to incorporate the NIS users...

I also had an instance today where my playbook worked perfectly (i.e., lineinfile did NOT overwrite the then-last entry for the 'ntp' user...) so looks like it's also an intermittent problem.

Just wanted to report a seeming problem, and see if there was a solution...

Thanks,
Will

[Michael DeHaan]

Can you let us know why the user module won't work for you in this case?   It should not be needed to edit those files directly, and if there's a missing feature I'd like to see it exposed in the user module.

Thanks!

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[Willard Dennis]

Hi Michael,

Sorry for the much-delayed response (again...)

This is kind of an edge-case, but for a NIS client (with 'compat' in the /etc/nsswitch.conf for passwd, which is at least the default in Ubuntu), you must add a special entry in to "pick up" the NIS users (again, see section 7.2 in http://www.linux-nis.org/nis-howto/HOWTO/settingup_client.html for the different options.)

I believe the 'user' module has the paradigm of adding actual users to the system, and can not just add needed entries to /etc/passwd (and /etc/shadow) to handle as case as the above... Or did I misread the docs on the user module?

I found that one can "get around" the need for such an entry in /etc/passwd if you specify the following in nsswitch.conf:

passwd:     files nis

i.e., try the local /etc/passwd first, then if not found, try NIS -- this is what we were doing, so we found the entry of '+::::::' was actually not necessary in /etc/passwd (and why the incorrect '::::::+' we had been putting in there didn't matter, and why NIS worked anyways)

Best,

Will