Filesystem Configuration: Key Takeaways (RHEL 8/9)

1) Create & tune filesystems

• Create: mkfs.xfs, mkfs.ext4 (via mke2fs backend).
• Labels/UUID: xfs_admin -L DATA /dev/<dev>, e2label /dev/<dev> DATA; prefer mounting by LABEL= or UUID= in /etc/fstab.
• Ext* tuning: tune2fs, inspect with dumpe2fs -h, low-level tasks with debugfs.
• XFS tools: xfs_info, grow online with xfs_growfs; repair with xfs_repair (offline).

2) Mounting & automounting

• Static mounts: manage in /etc/fstab; verify with findmnt and mount -a.
• On-demand mounts: use autofs for many dynamic keys or mixed backends; simple cases can use systemd.automount.
• Example (fstab + automount):

  UUID=...  /data  xfs   defaults,noatime  0 0
  server:/export/projects  /mnt/projects  nfs  noauto,x-systemd.automount,x-systemd.idle-timeout=120  0 0

3) Monitoring usage & quotas

• Capacity: df -hT, lsblk -f, findmnt -t xfs,ext4.
• Per-path usage: du -sh /path.
• Quotas: enable in fstab (usrquota,grpquota for ext4; uquota,gquota for XFS). Manage with xfs_quota (XFS) or edquota/repquota (ext*).

4) Synchronization & migration

• Prefer rsync over SSH for integrity and speed:

  rsync -aHAX --info=progress2 /src/ host:/dst/

• Validate with checksums (sha256sum) when migrating critical data.

5) Security-minded defaults

• Apply mount options where appropriate: nodev, nosuid, noexec on untrusted paths (e.g., /tmp, removable media, autofs keys).
• Honor SELinux contexts; use ls -Z and restorecon -R after moves.
• Automounting is convenient but widens the attack surface—scope keys narrowly and set idle timeouts.

6) Troubleshooting

• Logs: journalctl -xe, journalctl -u autofs.
• Mount health: findmnt, cat /proc/mounts.
• Repairs: ext* with fsck.ext4/e2fsck (unmounted), XFS with xfs_repair (requires unmount).
• Low space: identify heavy paths (du -xhd1 /), rotate/purge logs, and consider LVM + xfs_growfs for online growth.

Learning objectives achieved

1. Create and label filesystems; understand when to use ext4 vs XFS.
2. Tune/inspect ext* (tune2fs, dumpe2fs, debugfs) and manage XFS (xfs_* tools).
3. Configure static mounts (/etc/fstab) and on-demand mounts (autofs / systemd.automount).
4. Synchronize data safely with rsync.
5. Monitor capacity and enforce quotas.
6. Troubleshoot common issues: low space, corruption, failed mounts.

Glossary (modernized)

1. Automounter: Service that mounts targets on first access and unmounts after idle timeout (autofs or systemd.automount).
2. Map file: For autofs, associates keys with mount targets (e.g., /etc/auto.master → /etc/auto.nfs).
3. Block size: Allocation unit of a filesystem; affects performance trade-offs.
4. Label/UUID: Stable identifiers used in /etc/fstab to avoid device-name drift.
5. Quota: Limits on disk usage (per user/group or project) enforced by the filesystem.

Administering Local Filesystems - Quiz