dmesg: read the logs in the kernel ring buffer
lslocks: list current file locks
lslogins: info about users
whereis: locate man pages and binaries of a command (program)
findmnt: locate mounted filesystems, mount points
stat: file information/statistics

fdisk package
output of ps, dmesg

df, du, xdu
mkfs, fsck, lsof
sar, dstat, vmstat
baobab, kdiskstat
sudo sysctl vm.block_dump=1
tail -f /var/log/kern.log