Systemd – using the “+” prefix with ExecStartPre

systemd

According to systemd's service documentation, a + may be used as a prefix in systemd service configurations.

I am trying to use it like this:

[Service]
ExecStartPre=+/usr/bin/tomcat1
Type=simple
Environment="NAME=tomcat1"
EnvironmentFile=/etc/sysconfig/tomcat1
ExecStart=/usr/libexec/tomcat/server start
SuccessExitStatus=143
User=tomcat
Group=tomcat

I want to run /usr/bin/tomcat1 with elevated privileges, but doing so with the "+" sign gives the following error (note, "-" does not give an error).

"systemd[1]: [/usr/lib/systemd/system/tomcat1.service:10] Executable path is not absolute, ignoring: +/usr/bin/tomcat1"

I've also tried ExecStartPre="+/usr/bin/tomcat1, ExecStartPre="+"/usr/bin/tomcat1, etc.

I know I can use PermissionsStartOnly=true as an alternative, which should work, but that seemed less than ideal.

Best Answer

The documentation that you are using does not match the version of systemd that you are using. The "+" modifier was introduced in version 231.

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Systemd: default value for environment variable

systemd is not a shell, so it does not support shell-specific substitutions in environment files. Their format is simply KEY=VALUE, with possible empty lines and comments in between.

To quote systemd.exec(5):

Settings from these files override settings made with Environment=. If the same variable is set twice from these files, the files will be read in the order they are specified and the later setting will override the earlier setting.

So, you can accomplish your task by either:

using multiple EnvironmentFile= directives (they override each other in the order of specification)
using Environment= in the service file to specify default values (any EnvironmentFile= will override it)

Systemd: permission issue with mkdir & ExecStartPre

You need to add

PermissionsStartOnly=true

to [Service]. Your user FOOd is of course not authorized to create a directory in /var/run. To cite the man page:

Takes a boolean argument. If true, the permission-related execution options, as configured with User= and similar options (see systemd.exec(5) for more information), are only applied to the process started with ExecStart=, and not to the various other ExecStartPre=, ExecStartPost=, ExecReload=, ExecStop=, and ExecStopPost= commands. If false, the setting is applied to all configured commands the same way. Defaults to false.

Best Answer

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Systemd: default value for environment variable

Systemd: permission issue with mkdir & ExecStartPre

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