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graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,734

Website

Systemd service run as user but run a pre and post as root [SOLVED]

Goal: write a systemd service to run the ExecStart= line as an unprivileged user BUT have ExecStopPost= and ExecStartPre= lines run as root.

Is this possible?  For example, the following will start the program as the unprivileged user:

[Unit]
Description=my service
After=remote-fs.target

[Service]
User=myuser
Group=mygroup
ExecStart=/usr/bin/myscript
Restart=on-failure

[Install]
WantedBy=multi-user.target

But what I really want is to have root run a 2nd program both before and after (ExecStartPre and ExecStartPost or an equivalent).  I can achieve the goal by omitting the User= and Group= lines from the service and by modifying /usr/bin/myscript to run certain lines within as myuser:mygroup but, I'd like to do it with entirely with systemd if possible.  I would be OK with a solution involving multiple .service units but am unsure how to make them conditional on this one.

Thoughts are appreciated.

Last edited by graysky (2018-10-08 20:11:06)

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Slithery

Administrator

From: Norfolk, UK

Registered: 2013-12-01

Posts: 5,776

Re: Systemd service run as user but run a pre and post as root [SOLVED]

Another option may be using sudo and some NOPASSWD entries in sudoers, but that dosn't fulfil the systemd only criteria either.

That's the best I've got

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loqs

Member

Registered: 2014-03-06

Posts: 19,113

Re: Systemd service run as user but run a pre and post as root [SOLVED]

Have you read the Special executable prefixes table in man 5 systemd.service?

graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,734

Website

Re: Systemd service run as user but run a pre and post as root [SOLVED]

Have you read the Special executable prefixes table in man 5 systemd.service?

Great pointer!  Thank you, this fits the bill.

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AUR packages • Zsh and other configs

eschwartz

Fellow

Registered: 2014-08-08

Posts: 4,097

Re: Systemd service run as user but run a pre and post as root [SOLVED]

If that weren't the case, you could still implement privilege dropping by using

/usr/bin/runuser -u username command args

systemd's User and Group keywords make this easier and reduce boilerplate, but it isn't impossible to do without.

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