Using variable in command path for ExecStart in systemd service [closed] - linux

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Im trying to make a systemd service like below :
[Unit]
Description=Syslog
[Service]
Type=simple
Environment="TESTEXTSERVICESFILES=/opt/test/extservices"
Environment="TESTCONFDATA=/storage/test/conf"
ExecStartPre=/bin/echo ${TESTEXTSERVICESFILES}/syslog/bin/nxlog $TESTCONFDATA
ExecStart=/opt/test/extservices/syslog/bin/nxlog -c ${TESTCONFDATA}/syslog/nxlog.conf
#ExecStart=/${TESTEXTSERVICESFILES}/syslog/bin/nxlog -c ${TESTCONFDATA}/syslog/nxlog.conf
[Install]
WantedBy=multi-user.target
After running 'sudo systemctl daemon-reload ; sudo systemctl start test-syslog ; sudo systemctl status test-syslog', I get the following success output:
● test-syslog.service - TestSyslog
Loaded: loaded (/usr/lib/systemd/system/test-syslog.service; enabled; vendor preset: disabled)
Active: deactivating (stop-sigterm) since Fri 2018-02-23 10:15:09 UTC; 11ms ago
Process: 9474 ExecStart=/./opt/test/extservices/test-syslog/bin/nxlog -c ${TESTCONFDATA}/test-syslog/nxlog.conf (code=exited, status=0/SUCCESS)
Process: 9471 ExecStartPre=/bin/echo /.${TESTEXTSERVICESFILES}/test-syslog/bin/nxlog $TESTCONFDATA (code=exited, status=0/SUCCESS)
Main PID: 9474 (code=exited, status=0/SUCCESS)
CGroup: /system.slice/test-syslog.service
└─9478 /./opt/test/extservices/test-syslog/bin/nxlog -c /storage/test/conf/test-syslog/nxlog.conf
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: test-syslog.service: control process exited, code=exited status=0
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: test-syslog.service got final SIGCHLD for state start-pre
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: About to execute: /./opt/test/extservices/test-syslog/bin/nxlog -c ${TESTCONFDATA}/test-syslog/nxlog.conf
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: Forked /./opt/test/extservices/test-syslog/bin/nxlog as 9474
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: test-syslog.service changed start-pre -> running
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: Job test-syslog.service/start finished, result=done
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: Started Test Syslog.
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: Child 9474 belongs to test-syslog.service
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: test-syslog.service: main process exited, code=exited, status=0/SUCCESS
Feb 23 10:15:09 lt-x260-1606.test.local systemd[1]: test-syslog.service changed running -> stop-sigterm
Here the service has started successfully. But when I comment the first ExecStart directive and uncomment the second one I get
as failure :
● test-syslog.service - Test Syslog
Loaded: loaded (/usr/lib/systemd/system/test-syslog.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Fri 2018-02-23 10:11:44 UTC; 11ms ago
Process: 9243 ExecStart=/$TESTEXTSERVICESFILES/test-syslog/bin/nxlog -c $TESTCONFDATA/test-syslog/nxlog.conf (code=exited, status=203/EXEC)
Process: 9239 ExecStartPre=/bin/echo /.${TESTEXTSERVICESFILES}/test-syslog/bin/nxlog $TESTCONFDATA (code=exited, status=0/SUCCESS)
Main PID: 9243 (code=exited, status=203/EXEC)
Feb 23 10:11:44 lt-x260-1606.test.local echo[9239]: /./opt/test/extservices/test-syslog/bin/nxlog /storage/test/conf
This time the service cannot start, like it doesnt want to start the process starting by ${TESTEXTSERVICESFILES} variable. Does someone have any idea why it is not working even if command lines are the same in both cases ?

Answer 1

You can't use variables in the actual command. systemd.service:
The command to execute must be an absolute path name. It may contain
spaces, but control characters are not allowed.
You might wan't to wrap it in a shell command (which does parameter expansion):
ExecStart=/bin/bash -c '/${TESTEXTSERVICESFILES}/syslog/bin/nxlog -c ${TESTCONFDATA}/syslog/nxlog.conf'

Answer 2

Instead of Environment=, use EnvironmentFile=, to define multiple environment variables.
[Service]
Type=simple
EnvironmentFile=/etc/sysconfig/customsyslog
ExecStart=/bin/echo ${TESTEXTSERVICESFILES}/syslog/bin/nxlog $TESTCONFDATA
/etc/sysconfig/customsyslog would contain key=value pair, e.g.,
TESTEXTSERVICESFILES=/opt/test/extservices
TESTCONFDATA=/storage/test/conf

Answer 3

An old message that I've just stumbled on but looks like your ExecStart line that doesn't work may have 2 '/' at the beginning. One from the ExecStart line before the variable and one from the variable which is declared as /opt/test/extservices
Just a thought.