LPIC-2 201-450: Filesystem and Devices study guide

Filesystem and Devices tests creating, mounting, checking, growing and limiting filesystems, plus the device interfaces that expose kernel state.

Rules and tools

mkfs.ext4 and mkfs.xfs create filesystems; e2fsck checks ext4 and xfs_repair checks XFS. Check ext4 offline or read-only.
ext4 grows online with resize2fs; XFS grows with xfs_growfs on the mountpoint and cannot shrink.
/etc/fstab fields are device, mountpoint, type, options, dump, pass. Prefer UUID= from blkid over kernel device names.
mount -o remount,ro / changes state; mount -a validates fstab; noatime reduces metadata writes.
Swap: mkswap, swapon, swapoff; fstab entry none swap sw 0 0.
Quotas need usrquota/grpquota mount options, quotacheck -cug, quotaon, then edquota and repquota.
udev rules live in /etc/udev/rules.d; /proc and /sys are kernel interfaces, not ordinary files.

Worked example

An ext4 filesystem on /dev/vg/data, mounted at /data, is full. Run lvextend -L +10G /dev/vg/data, then resize2fs /dev/vg/data while mounted. If it were XFS, use xfs_growfs /data instead. Reasoning: the block device must grow first, then the filesystem; ext4 supports online growth, while XFS grows to the device size via its mountpoint.

Traps

Running fsck on a mounted read-write filesystem.
Relying on /dev/sdb names that can reorder.
Forgetting quota mount options or the fstab pass field.
Trying to shrink XFS.