For those who like htop-style system monitoring tools, you should also keep these commands handy:

- atop (great for finding out what's causing system-wide slowness when you're not sure whether it's CPU/disk/network/temperature/etc.)

- iotop/iftop/sar (top equivalents for disk IO, network traffic, and sysstat counters)

- glances/nmon/dstat/iptraf-ng (pretty monitoring CLI-GUI utils with more colors)

- systemd-analyze blame (track down cause of slow boot times)

- docker stats (htop equivalent for docker containers)

- zpool iostat -v <poolname> 1 (iotop equivalent for ZFS pools)