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read-onlyno known side effects Compatibility
LinuxVerified for Linux using posix, bash, zsh syntax.
Operational knowledgereview due 2027-01-19
Requirementsjournalctljournalctl must be installed and available on PATH.
Version supportjournalctl Current supported releasesVerified for linux using posix, bash, zsh syntax; consult compatibility notes for platform-specific differences.
Expected signalsJul 23 08:14:22 web-01 systemd[1]: backup.service: Failed with result 'exit-code'.Representative successful output; values vary with the selected target and system state.
Known errorsjournalctl: command not foundjournalctl is missing or is not available on PATH.
Verifyjournalctl -p err -bThe output matches the expected target and exits without an error.Rollback noteNot required: this command is read-only and does not change system state.
Command breakdown
01journalctlCommandRuns the journalctl stage of this one-liner.
02-pOptionSelects the command-specific port, process, or print mode.
03errArgumentPasses err to journalctl.
04-bOptionConfigures journalctl with the -b option.
Example input
journalctl -p err -b
Example output
Jul 23 08:14:22 web-01 systemd[1]: backup.service: Failed with result 'exit-code'.
Jul 23 08:14:22 web-01 systemd[1]: Failed to start Nightly backup.
Jul 23 09:02:11 web-01 sshd[8124]: error: kex_exchange_identification: Connection closed by remote host
Illustrative output — exact values vary by system and data.
Runbooks
Official sources