Find failed services
Read-onlysystemctl --failed --no-pagerExpect: An empty list means no systemd units are currently marked failed.
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Essential check 3 / 3
03 / FIELD NOTES
Check services and listening ports
List failed systemd units, listening ports, and recent errors.
Why this way
Look at actual service state before restarting things. A port conflict or a clear error log often explains a failed deployment.
When to use
After installing a service, or when a web application does not respond.
When not to
These commands assume systemd. On Alpine (OpenRC) use rc-status and the logs under /var/log.
Prerequisites
- A systemd system (Debian, Ubuntu, Rocky, AlmaLinux). Alpine uses rc-status instead
- root or sudo to inspect all process information
Steps
Inspect TCP listeners
Read-onlysudo ss -lntpExpect: Check which process owns a port and whether it binds to loopback or all interfaces.
Read recent boot errors
Read-onlysudo journalctl -p err -b -n 30 --no-pagerExpect: Read the error before making changes. Logs may contain private information.
What it changes
Read-only. Does not restart services or change firewall rules.
Essential checks
Related
{
"slug": "service-health",
"risk": "safe",
"tags": [
"systemd",
"ports",
"logs",
"linux"
],
"updated": "2026-10-30",
"pathIndex": 3,
"why": "Look at actual service state before restarting things. A port conflict or a clear error log often explains a failed deployment.",
"steps": [
{
"command": "systemctl --failed --no-pager",
"risk": "safe"
},
{
"command": "sudo ss -lntp",
"risk": "safe"
},
{
"command": "sudo journalctl -p err -b -n 30 --no-pager",
"risk": "safe"
}
]
}