pidstat -p PID  # pidstat -p ALL
pidstat -p PID INTERVAL
pidstat -p PID INTERVAL QUANTITY
pidstat -C NAME  # by name

# custom stats
pidstat -p PID -r  # memory
pidstat -p PID -u  # cpu
pidstat -p PID -d  # io

# formatting
pidstat -p PID -t  # tree
pidstat -p PID -h  # horizontal ( for export )

netstat --tcp --udp --listening --program --numeric  # netstat -tulpn

iotop

iftop

htop

netstat --route --numeric  # netstat -rn

systemctl enable --now SERVICE  # chkconfig SERVICE on
systemctl disable --now SERVICE  # chkconfig SERVICE off
systemctl is-enabled SERVICE  # chkconfig SERVICE
systemctl daemon-reload  # chkconfig SERVICE --add

systemctl start SERVICE  # service SERVICE start
systemctl stop SERVICE  # service SERVICE stop
systemctl status SERVICE  # service SERVICE status
systemctl restart SERVICE  # service SERVICE restart
systemctl reload SERVICE  # service SERVICE reload

systemctl list-units --type=service --state=running --all  # service --status-all

journalctl --follow --since=today  # tail --follow /var/log/{messages,syslog}
journalctl --dmesg
journalctl --unit SERVICE
journalctl --grep 'fail|error|fatal'
journalctl --output json

journalctl --list-boots
journalctl --boot BOOT_ID

ps -C 'firefox' -O rss \
| awk '
    {
        count ++; sum += $2
    }
    END {
        count --
        print "Number of processes:\t\t\t",             count
        print "Average memory usage per process:\t",    sum/1024/count, "MB"
        print "Total memory usage:\t\t\t",              sum/1024,       "MB"
    }
'