在systemd服务中使用变量作为ExecStart命令路径

Question

我试图创建一个类似下面的systemd服务：

[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

运行 'sudo systemctl daemon-reload ; sudo systemctl start test-syslog ; sudo systemctl status test-syslog' 后，我得到了以下成功输出：

● 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

这里服务已经成功启动了。但是当我注释掉第一个ExecStart指令并取消注释第二个指令时，我遇到了失败：

● 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

这一次服务无法启动，就像它不想启动由${TESTEXTSERVICESFILES}变量开启的进程。有人知道为什么即使命令行在两种情况下都相同，它仍然无法正常工作吗？

- Mistrale

Answer 1

您无法在实际命令中使用变量。systemd.service：

要执行的命令必须是绝对路径名。它可以包含空格，但不允许控制字符。

您可能需要将其包装在一个 shell 命令中（该命令执行参数扩展）：

ExecStart=/bin/bash -c '/${TESTEXTSERVICESFILES}/syslog/bin/nxlog -c ${TESTCONFDATA}/syslog/nxlog.conf'

- Jürgen Hötzel

---

在我的情况下，我必须添加 exec：ExecStart=/bin/bash -c 'exec $VAR'。 - Benedikt Köppel

Answer 2

使用EnvironmentFile=而不是Environment=来定义多个环境变量。

[Service]
Type=simple
EnvironmentFile=/etc/sysconfig/customsyslog
ExecStart=/bin/echo ${TESTEXTSERVICESFILES}/syslog/bin/nxlog $TESTCONFDATA

/etc/sysconfig/customsyslog 文件中包含 key=value 对，例如：

TESTEXTSERVICESFILES=/opt/test/extservices
TESTCONFDATA=/storage/test/conf

- iamauser

---

是的，我知道，我只是想在测试服务之前让它工作 :) - Mistrale

Answer 3

我刚发现的一条旧消息，但看起来你的ExecStart行不起作用可能在开头有2个'/'。一个来自变量前的ExecStart行，另一个来自声明为/opt/test/extservices的变量。只是一个想法。

- cander