Watch each command run in a real-looking terminal, see what every part of it means, then try it yourself with practice tasks. From ls to kubectl.
The first three commands on any server: where am I, what's here, and how full is the disk.
Find what's filling the disk, list block devices, mount filesystems and check them.
dfReport used and free space per filesystemBeginnerduFind out which files and directories use the spaceBeginnerlsblkList disks, partitions and where they are mountedBeginnerfdiskView and edit a disk's partition tableIntermediatemountAttach a filesystem to the directory treeIntermediateumountDetach a mounted filesystem safelyBeginnermkfsCreate a filesystem on a disk or partitionIntermediatefsckCheck and repair a filesystemIntermediateblkidShow filesystem type, UUID and label of devicesBeginnerddCopy and convert raw data block by blockIntermediate