What's changed: Initial version (topic 1.05, subtopics 1.05.1–1.05.3)
5.3Creating, Managing, and Mounting Filesystems
Learn to make partitions usable: creating filesystems with mkfs (traits of ext4, XFS, VFAT, Btrfs, tmpfs), swap (mkswap, swapon/swapoff), mount/umount, boot-time mounts in /etc/fstab, identification by UUID and label, and /media.
A fresh partition is still "bare land". Only after you create (format) a filesystem and mount it somewhere in the directory tree can files live there. Unlike Windows drive letters, Linux joins everything into one tree.
5.3.1Creating filesystems
- Create with the mkfs family (
mkfs.ext4 /dev/sdb1,mkfs.xfs,mkfs.vfat;mkfs -t ext4is equivalent). Data is destroyed—double-check the target device. - Traits: ext4 (the general-purpose Linux standard, journaling; its predecessor ext3 is the same journaling family, with ext4 as the successor), XFS (large-scale, parallel workloads; RHEL default), VFAT (FAT—interoperable with Windows; USB sticks, the ESP), Btrfs (new generation with built-in snapshots), tmpfs (in-memory, vanishes on reboot).
- Swap: initialize with
mkswap /dev/sdb2, enable with swapon (disable with swapoff); check viaswapon --show.
5.3.2Mounting and /etc/fstab
- Manual:
mount /dev/sdb1 /data(/data is the mount point); detach withumount /data(fails while busy—a shell or process inside blocks it). - Boot-time mounts: one line in /etc/fstab (device, mount point, FS type, options, dump, fsck order).
mount -aapplies fstab now—essential to verify before rebooting. - Prefer UUID (
UUID=xxxx-…) or label (LABEL=data)—immune to device-order changes where /dev/sdb becomes /dev/sdc. Inspect with blkid. - Removable media mounts under /media (auto-mounted by desktops). Allow non-root users to mount via the user option in fstab.
Staples: Windows-shared USB = VFAT, in-memory temp space = tmpfs, swap = mkswap then swapon, fstab is robust with UUID/LABEL, umount fails → something is using it (find with lsof/fuser). Editing fstab and rebooting without mount -a verification—then failing to boot—is the classic failure both in practice and on the exam.
Finish with the full disk-addition workflow:
① confirm the new disk (/dev/sdb) with fdisk -l →
② partition it (previous section) →
③ mkfs.ext4 /dev/sdb1 to create the filesystem →
④ mkdir /data && mount /dev/sdb1 /data for a trial mount →
⑤ note the UUID via blkid /dev/sdb1 and append UUID=xxxx /data ext4 defaults 0 2 to /etc/fstab →
⑥ verify with umount /data && mount -a (catching typos here prevents an unbootable system). Journaling (ext4/XFS) records writes before applying them, keeping the filesystem consistent through power loss—reassurance for servers. tmpfs backs /tmp and fast scratch space, but remember: it consumes RAM and vanishes on reboot.
| Filesystem | Traits | Typical use |
|---|---|---|
| ext4 | General purpose, journaling | Default Linux choice |
| XFS | Large scale, parallel | RHEL-family default |
| VFAT | Windows-compatible | USB sticks, the ESP |
| tmpfs | In-memory, volatile | /tmp, fast scratch space |
Trap: "editing /etc/fstab mounts it immediately" is wrong—fstab is read at boot (and by mount -a); writing alone does nothing. "umount always detaches instantly" is wrong too—busy filesystems cannot be unmounted; identify users with lsof/fuser first. And "tmpfs survives reboots" is wrong (it lives in RAM).
5.3.3Section summary
- Create with mkfs.<type> (ext4 general, XFS large, VFAT interop, Btrfs new-gen, tmpfs in-memory); swap = mkswap → swapon
- mount/umount (not while busy); persist in /etc/fstab (prefer UUID/LABEL), verify with mount -a; removables under /media
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Quick check
(just a quick review)Q1. You want to format the new partition /dev/sdb1 as ext4. Which command?
Q2. You want /dev/sdb1 auto-mounted at /data on boot, robust against device-order changes. Which specification?
Q3. umount /data fails with "target is busy". Which explanation is correct?
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