systemd & fleet

SystemD

systemd is system & service manager that is also the PID 1 (root process) for some Linux operating systems (Fedora, NixOS, CoreOS)

 

its main function is process/service supervision on a single node

Fleet

fleet is distributed init system for CoreOS that abstracts over multiple systemd nodes

 

its main function is service supervision across a CoreOS cluster

systemd Architecture

fleet Architecture

systemd commands

# system control

$ systemctl --v
$ systemctl status [unit]
$ systemd-cgls
$ systemd-cgtop
$ systemctl
$ systemctl list-unit-files

# logs

$ journalctl [--user] -b 0

fleet Commands

# setup SSH tunnel (optional)

$ ssh -p port key_path user@ip
$ FLEETCTL_TUNNEL=ip:port

# control the fleet

$ fleetctl list-machines [-l]
$ fleetctl list-units
$ fleetctl list-unit-files
$ fleetctl status unit
$ fleetctl journal unit

Let's Configure a Service

[Unit]
Description=ApacheService # Let's create an apache service

[Service]
Restart=always
TimeoutStartSec=0
ExecStartPre=-/usr/bin/docker kill apache1
ExecStartPre=-/usr/bin/docker rm apache1
# we pull in the apache docker container if it doesn't exist yet
ExecStartPre=/usr/bin/docker pull coreos/apache
ExecStart=/usr/bin/docker run -rm --name apache1 -p 80:80 coreos/apache /usr/sbin/apache2ctl -D FOREGROUND
ExecStop=/usr/bin/docker stop apache1

[X-Fleet]
# can only run on this machine
X-ConditionMachineID=8acfff1514a64552a1a252f7da989aec 
# must only run on machines with this metadata
X-ConditionMachineMetadata="diskType=SSD"

# there are more options available, check the fleet docs and systemd docs

Execute!

# systemd --system unit file locations
$ ls /usr/lib/systemd/system
$ ls /etc/systemd/system
$ ls /run/systemd/system

# systemd  --user unit file locations
$ ls /usr/lib/systemd/user
$ ls /etc/systemd/user
$ ls /run/systemd/user
$ ls $HOME/.config/systemd/user
$ ls $XDG_CONFIG_HOME/systemd/user

Here are where all the unit files should be:

# add your metadata to fleet.conf
$ cat /etc/fleet/fleet.conf

metadata="diskType=SSD"

# create the file apache.service
$ cd ~
$ fleetctl submit apache.service
$ fleetctl list-units
# its going to pull the container first
$ fleetctl start apache.service
$ fleetctl status apache.service
$ fleetctl journal apache.service

# see its a docker container!
$ docker ps

CONTAINER ID        IMAGE                       COMMAND                CREATED             STATUS              PORTS                NAMES
0fcee3ab621d        coreos/apache:latest        /usr/sbin/apache2ctl   2 minutes ago       Up 2 minutes        0.0.0.0:80->80/tcp   apache1

# check if it works
$ curl 127.0.0.1

<html><body><h1>It works!</h1>
<p>This is the default web page for this server.</p>
<p>The web server software is running but no content has been added, yet.</p>
</body></html>

That's just the beginning

  • http://www.freedesktop.org/wiki/Software/systemd/
  • https://coreos.com/
  • http://matrix.ai/
  • http://nixos.org/

systemd & fleet

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systemd & fleet

Lightning Talk about systemd & Core OS's fleet

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