Command reference
Most Useful Commands for Troubleshooting
Inspection-first commands for narrowing problems without changing the system too early.
journalctl
Reads the systemd journal.
journalctl [options]
systemctl
Controls systemd services and system state.
systemctl [command] [unit]
dmesg
Reads kernel ring buffer messages.
dmesg [options]
tail
Shows the last lines of a file or follows new output.
tail [options] [file]
grep
Searches text for matching patterns.
grep [options] pattern [file...]
watch
Runs a command repeatedly and shows changing output.
watch [options] command
ping
Tests basic network reachability with ICMP echo requests.
ping [options] host
curl
Transfers data with URLs.
curl [options] URL
dig
Queries DNS records.
dig [options] name [type]
ss
Inspects sockets and listening ports.
ss [options]
df
Shows filesystem disk space usage.
df [options] [path]
du
Estimates file and directory space usage.
du [options] [path]
free
Shows memory usage.
free [options]
lscpu
Displays CPU architecture information.
lscpu