Troubleshooting systemd Error 203/EXEC While Starting Chronos

Recently, while trying to start the Chronos service using systemctl, I encountered the following error:

systemctl start chronos

Upon checking the status:

chronos.service: Control process exited, code=exited status=203/EXEC

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Root Cause

The error status=203/EXEC means that systemd failed to execute the service script. Common reasons include:

1. Missing shebang (#!/bin/bash) at the top of the script.

2. Incorrect file permissions — in this case, the script had chmod 777, which is too permissive and not allowed by systemd.

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Resolution Steps

Here’s what I did to resolve it:

1. Added the shebang to the script:

   #!/bin/bash

   Placed at the very top of /etc/rc.d/init.d/chronos.

2. Corrected the script permissions:

   chmod 755 /etc/rc.d/init.d/chronos

3. Verified that the script works manually:

   /etc/rc.d/init.d/chronos start

4. Restarted the service:

   systemctl start chronos

This time, the service started successfully and showed active (exited), which is expected behavior for SYSV-style scripts.

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Recommendation

While the issue is resolved, consider migrating to a native systemd unit file for better process management, logging, and compatibility. Legacy init scripts work, but native units provide more control and clarity.