Sat, 16 Sep 2017

Restic Systems Backup Setup, Part 2 - Running minio under runit under systemd

Part 2 of my series on building a restic-based system backup setup. Part 1 can be found found here.

As described in Part 1, my general strategy is to have a centralized backup server at a particular location, running an instance of minio for each server being backed up. In essence, I'm going to want to be running N minio server --config-dir=/... instances, and I want a simple way to add and start instances, and keep them running. In essence, I want a simple init service.

Fortunately, if you're looking for a simple init service, you need look no further than runit. It's an incredibly tiny init-like system, composed of some simple tools: runsv to run a service, keep it up and optionally log stdout output somewhere; sv to control that service by simply talking to a socket; and runsvdir to keep a collection of runsv instances going. Defining a service is simple, in a directory there is a run file, which is used by runsv to start the service. If you want to log, create a log subdirectory, with it's own run file — that file is executed and given the stdout of the main process as its input (the included svlogd command is a simple process for handling logs). To run a bunch of runsv instances, put them (or symlinks to them) all in a single directory, and point runsvdir at it. As a bonus, runsvdir monitors that directory, and if a runsv directory is created or goes away, runsvdir does the right thing.

It's an incredibly useful set of commands, and allows you to manage processes fairly easily. In this case, every time I add a machine to this backup scheme, I make an appropriate runsv dir with the correct minio incantation in the run file, and just symlink it into the runsvdir directory. We've been using runit at work for quite a while now in containers, and it's an awsome tool.

My newly-minted backup server is running Debian Stretch, which uses systemd as its init system. Creating systemd unit files is still something I have to think about hard whenever I do it, so here's the one I use for runit:

[Unit]
Description=Backup Service Minio Master runsvdir

[Service]
ExecStart=/usr/bin/runsvdir -P /backups/systems/conf/runit/
Restart=always
KillMode=process
KillSignal=SIGHUP
SuccessExitStatus=111
WorkingDirectory=/backups/systems
User=backups
Group=backups
UMask=002

[Install]
WantedBy=multi-user.target
    

Here, systemd starts runsvdir, pointing it at my top-level directory of runsv directories. It runs it as the backups user and group, and makes it something that starts up once the system reaches "multi-user mode".

Part 3 is coming, where I'll document backing up my first system.

Posted at: 18:41 | category: /computers/backups/restic-systems-backups | Link