When operating services on Linux, you may often see the following status in the output of systemctl status:

Active: failed (Result: exit-code)
Unit entered failed state

This message means that systemd has determined the service failed to start or run correctly.
Below is a three-step routine to quickly diagnose and resolve this error.

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Check service status and termination cause #

First, check the service status and the reason it terminated.

sudo systemctl status [service-name]

Here are the key points to look for.

Main PID
The process ID that exited and its state at the time of termination.

Result

• exit-code
  → The program terminated abnormally due to an internal error.
• signal
  → The process was forcibly terminated by an external signal (for example, the OOM Killer).

At this stage, the goal is not to determine where it failed,
but to identify what type of failure occurred.

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Analyze detailed logs with journalctl (core step) #

In most cases, systemctl status alone does not provide enough information.
The actual root cause is usually found in the journal logs.

sudo journalctl -u [service-name] -n 50 --no-pager

The following messages appear most frequently.

• Permission denied
  → File permissions or execution rights on binaries, config files, or log directories.
• Address already in use
  → Port conflict (another process is already using the port).
• syntax error, invalid config
  → Configuration file syntax errors.
• Out of memory, Killed process
  → The process was terminated by the kernel due to insufficient memory.

In most cases, the root cause is identified at this step.

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Common causes and fixes #

Cause	How to check	Solution
Configuration file error	Look for syntax error in journalctl	Fix .conf or .yaml syntax
Permission issue	Check file and directory permissions with ls -l	Fix permissions with chown or chmod
Port conflict	ss -tulpn | grep [port]	Stop the existing process or change the port
Dependency issue	systemctl list-dependencies [service-name]	Start required services first

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Required steps after configuration changes #

If you modify a .service file or any configuration file,
do not restart the service immediately.

sudo systemctl daemon-reload
sudo systemctl restart [service-name]

Without daemon-reload, systemd may continue using the previous configuration.

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Summary #

• Identify the failure type with systemctl status
• Find the real cause with journalctl -u
• After fixing the configuration, run daemon-reload and restart

Using this routine, most systemd failed states can be resolved within five minutes.

🛠 마지막 수정일: 2025.12.22