How to run systemd service as specific user and group in Linux

By default most of the systemd services are configured to run by root user but there is also an option to create a custom systemd service unit file and run it as a speciic user or group or both. So in this article we will check and verify the steps to run systemd service as specific user and group using CentOS/RHEL 7/8 Linux environment.

I have installed Oracle VirtualBox on a Linux server, where I will use a Virtual Machine with RHEL/CentOS 7/8 to verify the steps from this article.

 

Some more articles on similar topic:

 

Step 1: Overview on systemd

I hope you are already familiar with below topics

 

Step 2: Create user and Group

Now this is an optional steps assuming you already have your user and group ready for next steps. But if you do not then you can follow this article to create a new user and assign a custom group (primary or secondary) to the respective user.

Here I have already created a user deepak who is part of deepak and admin group

[root@centos-8 ~]# useradd deepak
[root@centos-8 ~]# passwd deepak  <-- Here the screen will prompt to assign a new password

To verify the groups of any user

[root@centos-8 ~]# id deepak
uid=1000(deepak) gid=1000(deepak) groups=1000(deepak),1001(admin)

So we wish to create a systemd service unit file and run systemd service as specific user and group which for us will be deepak user part of admin group

 

Step 3: Create Sample Script

We will use our startup script from old articles with some tweaks to check and run systemd service as specific user and group in Linux

[root@centos-8 ~]# cat /tmp/startup_script.sh
#!/bin/bash

if [[ `id -nu` != "deepak" ]];then
   echo "Not deepak user, exiting.."
   exit 1
fi

SCRIPT_NAME=$(basename -- "$0")

z=0
for i in {1..3}; do
    sleep 1m
    ((z++))
    echo "$SCRIPT_NAME: finished minute ${z}" >> /tmp/file
done
echo "$SCRIPT_NAME: COMPLETELY FINISHED" >> /tmp/file

So in this script we have added an explicit check for user, so unless the user executing the script is "deepak", the script will fail to execute. If successful the script will continue to write in /tmp/file for 3 minutes with 1 minute interval. This will also help us make sure that the script does not exits before completing it's defined task

Change the ownership of the script file to deepak

[root@centos-8 ~]# chown deepak:deepak /tmp/startup_script.sh

Provide executable permission to the script

[root@centos-8 ~]# chmod u+x /tmp/startup_script.sh

[root@centos-8 ~]# ls -l /tmp/startup_script.sh
-r-xr--r-- 1 deepak deepak 304 Jan 17 01:58 /tmp/startup_script.sh

We will execute the script manually to make sure it works as expected

[root@centos-8 ~]# /tmp/startup_script.sh
Not deepak user, exiting..

 

Step 4: Create unit file to run systemd service as specific user and group

Now as highlighted under step 1, I have already written another article with the steps to create a new systemd unit file. Here we will name our systemd unit file as run-as-user.service under /etc/systemd/system. Below is the content of run-as-user.service

[root@centos-8 ~]# cat /etc/systemd/system/run-as-user.service
[Unit]
Description=Run service as user deepak
DefaultDependencies=no
After=network.target

[Service]
Type=simple
User=deepak
Group=admin
ExecStart=/tmp/startup_script.sh
TimeoutStartSec=0
RemainAfterExit=yes

[Install]
WantedBy=default.target

Here we have defined User=deepak and Group=admin to make sure the script will be executed only as user deepak which is part of admin group.
You can also use many other directives if required in your environment such as WorkingDirectory, EnvironmentFile etc. For more information check man page of systemd.exec

Refresh the systemd configuration files

[root@centos-8 ~]# systemctl daemon-reload

Next enable the service (if required) to start automatically at boot

[root@centos-8 ~]# systemctl enable run-as-user.service
Created symlink /etc/systemd/system/shutdown.target.wants/run-as-user.service → /etc/systemd/system/run-as-user.service.

 

Step 5: Verify the systemd unit file configuration

Now since we are done with the setting up of systemd. Let us verify our configuration. Before starting I have cleared the content of /tmp/file which is where our script /tmp/startup_script.sh will place dummy content every minutes for 3 minutes.

We will only start the run-as-user.service runtime as a reboot is not required to validate the configuration here:

[root@centos-8 ~]# systemctl restart run-as-user.service

Next check the status of the service

[root@centos-8 ~]# systemctl status run-as-user.service
● run-as-user.service - Run service as user deepak
   Loaded: loaded (/etc/systemd/system/run-as-user.service; enabled; vendor preset: disabled)
   Active: active (exited) since Fri 2020-01-17 02:09:32 IST; 2h 31min ago
  Process: 24113 ExecStart=/tmp/startup_script.sh (code=exited, status=0/SUCCESS)
 Main PID: 24113 (code=exited, status=0/SUCCESS)

Jan 17 02:09:32 centos-8.example.com systemd[1]: Started Run service as user deepak.

Well looks like everything was good as we were able to run systemd service as specific user and group, you can check the ps status to make sure our script is running using below command:

[root@centos-8 ~]# ps -ef | grep startup
deepak   26877     1  0 04:42 ?        00:00:00 /bin/bash /tmp/startup_script.sh
root     26890  7625  0 04:42 pts/0    00:00:00 grep --color=auto startup

Now you can monitor the content of /tmp/file for couple of minutes as configured in the script

[root@centos-8 ~]# cat /tmp/file
startup_script.sh: finished minute 1
startup_script.sh: finished minute 2
startup_script.sh: finished minute 3
startup_script.sh: COMPLETELY FINISHED

 

Lastly I hope the steps from the article to run systemd service as specific user and group in CentOS/RHEL 7/8 Linux was helpful. So, let me know your suggestions and feedback using the comment section.

 

Related Searches: run service as user linux. systemd allow user to start service. systemd start service as user on boot. linux systemd service run as root. Restarting systemd service only as a specific user? systemd services fail with User= in service file. Start process as a specific user. how to run a service a non-root user completely?

11 thoughts on “How to run systemd service as specific user and group in Linux”

  1. Shouldn't systemd's "--user" feature be used to allow non-root accounts run their own services -- without bothering the root-wielding admin every time they want to change something?

    I'd love an actual example of that...

    Reply
  2. This is really helpful, thank you. It is also rather timely as I'm trying to get a service to work with a little twist and maybe you have some insight to this.

    I'm running VirtualBox with a Ubuntu 20.04 guest and a Windows 10 host. The VM is defined with a shared folder on the host.
    I need to run the service as my user and it has to create some files and directories in the shared folder.
    There are some really weird things happening.
    - I am unable to write anything to the shared folder when I run the script as a service. I always get "Permission Denied" errors.
    No problem if I run the service as "sudo service xxx start", only when it is started on system init. I specifically have an
    "After=.mount" in the Init section.

    - If I run using "+" before the script name on ExecStart, it runs as root and creates files, but then they just disappear. Actually,
    they show up only in the script (e.g. if I issue an "ls" command) but by the time I get to log in, they are gone.

    Anyway, I'm tearing what little hair I have out on this and can't get anywhere. Any insight would be greatly appreciated.

    Thanks
    Alan

    Reply
    • Sorry, I didn't realize I couldn't use angle brackets. My "After=.mount" should have been "After=shared-folder-dir.mount", copied from the systemctl list-units list.

      Reply
    • Hi Alan,
      If there is a requirement for a certain file system then instead of After= you should use RequiresMountsFor=/path/to/fs.
      Few questions:
      If you just run the script as the user, is the script able to perform write operations in the shared folder? - I assume yes?
      Because if this works, there is no reason it will fail as systemctl service.
      Or do you see problems writing at reboot stage?
      If I have more information, I may try to replicate the behaviour in my environment.

      Reply
  3. Thanks for the response and for taking a look at this, to answer your questions:

    - Just running the service after I log in, everything works, I can write to the shared folder with the service.
    - the really weird thing is that I have echo statements showing that when I run as root:
    - I can write to the shared folder
    - the script sees the files and directories via ls right after creation
    - they go away at some point. there is no delete for these files anywhere, but some of them are accessed
    by a java program that the script is calling. some are not. but they all disappear by the time I can log in
    and look.

    Reply
    • Thanks for sharing the additional information, I will not approve the script as that may be confidential.
      Give me time till tomorrow, let me try to replicate this and come back. I am also little occupied with my office work.
      I assume you are using samba for file sharing.
      We can further communicate using your mail address. You can send mail to admin@golinuxcloud.com

      Reply

Leave a Comment

Please use shortcodes <pre class=comments>your code</pre> for syntax highlighting when adding code.