Sysadmin

The future of configuration management – mini talks

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On March 7th I was at the DevOps Norway meetup where both Jan Ivar Beddari and me presented an extended version of the ignite talks we held at Config Management Camp in February. The talks were streamed and recorded through Hangouts and the recording is available on YouTube.

The meeting gave me the opportunity to explain in a bit more detail my viewpoint about why we need a completely new design for our configuration management tools. I had tried already in a blog post that caused some amount of controversy and it was good to get a second chance.

I’d recommend you watch both Jan Ivar’s talk and mine, but if you’re interested only in my part then you can check out here:

And don’t forget to check out the slides, both Jan Ivar’s and mine.

In reply to Luke Kanies

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shitIt didn’t take many hours for Luke Kanies to pick up my provocative blog post and express his disappointment:

I’m not going to complain for his words: if I was him I would have thought the same things, and maybe also written the same things. At the same time, it’s kind of funny that a lot of the inspiration for that post came from Luke himself. I’ll explain.

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systemd unit files for CFEngine

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systemd logoLearning more of systemd has been on my agenda since the release of Debian 8 “Jessie”. With the new year I decided that I had procrastinated enough, I made a plan and started to study according to the plan. Today it was time for action: to verify my understanding of the documentation I read up to now, I decided to put together unit files for CFEngine. It was an almost complete success and the result is now on GitHub for everyone to enjoy. I would appreciate if you’d give them a shot and report back.

Main goals achieved:

  1. I successfully created three service unit files, one for each of CFEngine’s daemons: cf-serverd, cf-execd and cf-monitord; the units are designed so that if any of the daemon is killed for any reason, systemd will bring it back immediately.
  2. I successfully created a target unit file that puts together the three service units. When the cfengine3 target is started, the three daemons are requested to start; when the cfengine3 target is stopped, the three daemons are stopped. The cfengine3 target completely replaces the init script functionality.

Goal not achieved: I’ve given a shot at socket activation, so that the activation of cf-serverd was delayed until a connection was initiated to port 5308/TCP. That didn’t work properly: systemd tried to start cf-serverd but it died immediately, and systemd tried and tried again until it was too much. I’ll have to investigate if cf-serverd needs to support socket activation explicitly or if I was doing something wrong. The socket unit is not part of the distribution on GitHub but its content are reported here below. In case you spot any problem please let me know.

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Managing system services with CFEngine

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An important system service is not running...

I have experienced that when people talk about a system’s configuration, they mostly think of software to be installed and configuration files to be deployed. That’s true, they are part of a system configuration, but there’s more to it — if Configuration Management was only that, you could rightfully call it “provisioning” instead. For example, another part of a system’s configuration is that certain critical services must be running and/or certain other services must not be running. And in fact, any configuration management tool has provisions to manage system services and ensure they are in the desired state (while they may differ a lot on the “when” and “how” and “how often” the state is checked).

CFEngine is no exception. You can take advantage of ready-to-use frameworks like NCF or EFL, or  roll your own checks. What I’m presenting you today is a simple bundle that I wrote called watch_service, that you can use to ensure that certain system services are up or down.

My approach is similar to NCF’s bundle called service_action in that it tries to provide a generic, system-agnostic bundle to manage services but with a few differences:

  • while service_action relies on information in NCF itself to make the bundle simpler to use, my watch_service relies only on CFEngine’s standard_services knowledge as available in the standard library;
  • while service_action returns information to the agent in the form of namespace-scoped classes (e.g.: the service was in the desired state, or the service was not in the desired state and the problem has been fixed successfully), watch_service only reports about the events by means of another bundle called report, whose code will be also provided in the last part of this post.
  • service_action supports many different actions, watch_service only supports “up” (ensure the service is running) or “down” (ensure the service is not running).

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Rudimentary compliance report for CFEngine

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In CFEngine community you don’t have a web GUI with compliance report. You can get them via EvolveThinking’s Delta Reporting, but if you can’t for any reason, you need to find another way.

A poor man’s compliance report at the bundle level can be extracted via the verbose output. This is how I’ve used it to ensure that a clean-up change in the policies didn’t alter the overall behavior:

cf-agent -Kv 2>&1 | perl -lne 'm{verbose: (/.+): Aggregate compliance .+ = (\d+\.\d%)} && print "$1 ($2)"'

These are the first ten lines of output on my workstation:

bronto@brabham:~$ sudo cf-agent -Kv 2>&1 | perl -lne 'm{verbose: (/.+): Aggregate compliance .+ = (\d+\.\d%)} && print "$1 ($2)"' | head -n 10
/default/banner (100.0%)
/default/inventory_control (100.0%)
/default/inventory_autorun/methods/'proc'/default/cfe_autorun_inventory_proc (100.0%)
/default/inventory_autorun/methods/'fstab'/default/cfe_autorun_inventory_fstab (100.0%)
/default/inventory_autorun/methods/'mtab'/default/cfe_autorun_inventory_mtab (100.0%)
/default/inventory_autorun/methods/'dmidecode'/default/cfe_autorun_inventory_dmidecode (100.0%)
/default/inventory_autorun (100.0%)
/default/inventory_linux (100.0%)
/default/inventory_lsb (100.0%)
/default/services_autorun (100.0%)

Not much, but better than nothing and a starting point anyway. There is much more information in the verbose log that you can extract with something slightly more elaborated than this one-liner. Happy data mining, enjoy!

The leap second aftermath

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TurnBackTimeThe leap second is finally behind us, and for the first time it has been transformed in an event. That had the unfortunate consequence that many channels where useful information had flown in the previous events were now flooded with bullshit. But it’s over. A giant army of idiots has finally stopped asking “what will you do with your extra second?”, a smaller but still noticeable army of inaccurate writers and journalists won’t write for a while that the atomic clocks need to be stopped for a second to realign with the Earth (?!?!?!?!?!?). We can now sit, look back and save some take-aways for the next edition of the event.

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How to make CFEngine recognize if systemd is used in Debian

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CFEngine 3.6 tries to understand if a Linux is using systemd as init system by looking at the contents of /proc/1/cmdline, that happens in bundle common inventory_linux. That’s indeed a smart thing to do but unfortunately fails on Debian Jessie, where you have:

root@cf-test-v10:~# ls -l /sbin/init
lrwxrwxrwx 1 root root 20 May 26 06:07 /sbin/init -> /lib/systemd/systemd

the pseudo-file in /proc will still report /sbin/init and as a result the systemd class won’t be set. This affects services promises negatively and therefore I needed to make our policies try to outsmart the inventory 😉 These promises, added in a bundle of ours, did the trick:

bundle common debian_info {
  vars:
    init_is_link::
      "init_link_destination"
          string => filestat("/sbin/init","linktarget") ;

  classes:
    init_is_link::
      "systemd"
          expression => regcmp("/lib/systemd/systemd",
                               "$(init_link_destination)"),
          comment => "Check if /sbin/init links to systemd" ;

    debian::
      "init_is_link"
          expression => islink("/sbin/init"),
          comment => "Detect if init is a link" ;
}

Notice that our bundle is actually bigger, I cut off all the promises that were not relevant for this post. Enjoy!