Modify systemd unit file without altering upstream unit file

Question

I have installed the pimd service by means of apt. This comes with an upstream systemd unit file (/lib/systemd/system/pimd.service).

I want the service to be restarted when for some reason it gets killed, hence I wish to add the line Restart = always in the unit file.

However, I don’t want to modify the upstream unit file.

Is there any workaround for this?

Closely related: [How to set environment variable in systemd service?](http://serverfault.com/q/413397/126632) — Michael Hampton, Mar 28 '17 at 20:31
Possible duplicate of [How to set environment variable in systemd service?](https://serverfault.com/questions/413397/how-to-set-environment-variable-in-systemd-service) — 030, Apr 18 '17 at 09:31

score 93 · Accepted Answer · edited Mar 18 '19 at 06:42

93

You have two options:

Copy the unit file from /lib/systemd/system/ to /etc/systemd/system/.
And then make your modifications in /etc/systemd/system/pimd.service to completely override the unit file(s) supplied by the package maintainer.

The command systemctl edit --full <service-name> automates this for you.
You can alter or add specific configuration settings for a unit, without having to modify unit files by creating .conf files in a drop-in directory /etc/systemd/system/<unit-name>.<unit-type>.d/
i.e. create a /etc/systemd/system/pimd.service.d/restart.conf

The command systemctl edit <service-name> performs these steps for you.

See man systemd.unit

edited Mar 18 '19 at 06:42

lkd

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answered Mar 28 '17 at 10:45

HBruijn

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The second option can be made easier by using `systemctl edit ` – muru Mar 29 '17 at 08:18
12

And the first one by using `systemctl edit --full `. – user1686 Mar 29 '17 at 09:50
2

Please restructure this answer so that the ```system edit``` commands come first in each section. It is much better to use the tools to avoid typos and misconfigurations. – null May 26 '20 at 13:52

score 28 · Answer 2 · edited Feb 03 '22 at 10:40

The RHEL documentation recommends two ways:

Extend the default unit file by creating a configuration directory and file under /etc/systemd/system/[name-goes-here].service.d/config_name.conf

In this case the file would need to contain something like this:

[Service]
Restart=always

This is what systemctl edit [name-goes-here] does, it creates that directory and override.conf within it.

Create a copy of the original unit file /usr/lib/systemd/system/ in /etc/systemd/system/ and make changes there.

I would try option one but they are both viable options. Either way remember to run systemctl daemon-reload after making the changes.

RHEL documentation on Creating and Modifying systemd Unit Files

score 3 · Answer 3 · edited May 08 '20 at 11:13

Consider using a script to read the upstream configuration, modify it, and spit it out to drop-in file.

For example, I use Chef and here's a piece of ruby (library) that parses marathon systemd unit file to get original ExecStart from it

require 'inifile'

module Dcos
  def get_execstart_from_unit_file
    marathon_systemd_unit_file = 
    IniFile.load('/etc/systemd/system/dcos-marathon.service')
    return marathon_systemd_unit_file['Service']['ExecStart']
  end
end

Then in the recipe, I create the drop-in file to append an option to ExecStart

chef_gem 'inifile'

exec_start_orig = get_execstart_from_unit_file

systemd_service_drop_in 'dcos-marathon' do
  override 'dcos-marathon.service'
  precursor 'Service' => { 'ExecStart' => nil }
  service do
    exec_start exec_start_orig + ' --env_vars_prefix "DCOS_MARATHON_"'
  end
end

Excellent, I'm also trying to achieve that with Chef! Thank you. — ZedTuX, May 08 '20 at 07:03
Looks like this `systemd_service_drop_in` method is not part Chef. Are you using the https://github.com/nathwill/chef-systemd cookbook? If that's the case, please tell it in your answer. — ZedTuX, May 08 '20 at 07:07

Modify systemd unit file without altering upstream unit file

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