# show current state for md0
cat /sys/block/md0/md/sync_action
# start scrubbing md0
echo check > /sys/block/md0/md/sync_action
# overall RAID status
cat /proc/mdstat
# show how many block mismatched occurred for md0
cat /sys/block/md0/md/mismatch_cnt

man md

btrfs scrub start /
btrfs scrub status /

man btrfs-scrub

dstat -tclmsgndrpy 60
## prints one line every minute containing:
## time, cpu-usage, load-avg, mem-usage, swap, paging, net-usage, disk-usage, io-ops, procs, int/csw

man dstat

forkstat -e exec

man forkstat

## counts since startup
cat /proc/interrupts
## counts refreshed every second
watch -n1 "cat /proc/interrupts"

## remove packages not needed anymore (like old kernels)
apt-get autoremove --purge
## delete downloaded package archives (.deb files)
apt-get clean

man apt-get

dpkg-query -l
dpkg-query -l 'foo*'

man dpkg-query

emerge --sync
emerge --ask --update --deep --newuse @world
emerge --depclean

man emerge