Hosting Operations
Read-only, can be slowFind the First Failure Line for One Unit
A failed service has repeated restart noise, and you need the earliest current-boot line that names an error or failed startup step.
Command
journalctl -u app-worker -b --no-pager -o short-iso | grep -m1 -E 'ERROR|Failed|status='Before you run this
System impact: Read-only. Can create load on large logs, directories, filesystems, or process tables.
When not to use it: Do not use this as a complete log review; it intentionally stops at the first matching line and can miss later, more specific evidence.
Expected output
The earliest current-boot app error, failed step, or status line for the unit.
System impact
Read-only, can be slow. Nothing changes. journalctl prints the current-boot unit log and grep stops at the first matching failure line.
Scope this to the smallest useful path or service on busy systems.
Recovery / rollback: no state is changed.
When to use it
Use when restart loops bury the original clue under repeated systemd retry messages.
When not to use it
Do not use this as a complete log review; it intentionally stops at the first matching line and can miss later, more specific evidence.
next steps
Related commands
Build a Restart Loop Timeline
Restart loops make more sense when you line up starts, failures, and counters.
journalctl -u app-worker -b --no-pager -o short-iso | grep -E 'Started|Failed|Scheduled restart|Main process exited'
Read Warning and Error Logs for One Failed Unit
Filter a failed unit's journal to the lines most likely to explain the stop.
journalctl -u app-worker -b -p warning..alert --no-pager -n 80
Group Journal Errors by Unit
A noisy incident usually has a noisy source.
journalctl -p err..alert --since "2 hours ago" --no-pager -o short-iso | awk '{split($3,a,"["); unit=a[1]; count[unit]++} END {for (u in count) print count[u], u}' | sort -nr
Summarize Journal Severity During an Incident
Start with severity counts before opening every log line.
journalctl -p warning..alert --since "2 hours ago" --no-pager -o short-iso | awk '{count[$4]++} END {for (level in count) print count[level], level}' | sort -nr
Print a Critical Journal Timeline
Timeline beats guesswork when several failures happen close together.
journalctl -p err..alert --since "2 hours ago" --no-pager -o short-iso | awk '{print $1, $3, $4, substr($0,index($0,$5))}'
Study mapping
Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.
Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.