Disk Formatting

---
name: disk-formatting
description: Format, repartition and mount disks/partitions on Fedora Linux (ext4, btrfs, NTFS, FAT32, exFAT). Use when the user asks to format a disk, create a partition, fix a read-only NTFS drive, wipe a disk, make a USB stick, or mount a formatted disk with fstab.
---


# Disk formatting on Fedora

Workflow: identify → confirm exact target and authorization → prefer non-destructive diagnosis → unmount/format/mount/fstab only when explicitly authorized → verify. Formatting, unmounting, fstab edits, and write tests are mutations; read-only review must stop before them.

## Safety rules

- **ALWAYS run `lsblk -f` first and confirm the exact device with the user before any destructive command.**
- Reformatting erases ALL data. Warn explicitly and list what the user will lose. Ask for confirmation with the `question` tool when the target holds data.
- Never format a mounted filesystem or the system disk (check `lsblk -f` MOUNTPOINTS: `/`, `/home`, `/boot` are system).
- Double-check that `sdb1` in the plan really is the user's data disk, not the installer stick or another disk with data.
- Use `sudo -n` only for a separately authorized operation; do not fall back to an interactive password prompt during autonomous review. Without authorization, stop at read-only inventory and record `unverified`.
- After `mkfs`, run `sync`.

## Why a disk can't be written to (check BEFORE reformatting)

Reformatting is the LAST resort, not the first fix. Most "can't create folder" cases have a non-destructive fix:

1. **NTFS mounted read-only** (`mount | grep fuseblk` shows `(ro,...)`, journal shows ntfs-3g "Read-Only"): the volume has a "dirty" flag from Windows fast startup / hibernation / unclean shutdown. Fix WITHOUT data loss:
   - `umount /dev/sdXN` (or `udisksctl unmount -b /dev/sdXN`)
   - `sudo ntfsfix /dev/sdXN` (clears dirty flag, does not touch data)
   - Remount (replug or `udisksctl mount -b /dev/sdXN`) and verify with `touch`.
   - Still read-only? Windows-side fix: disable Fast Startup (powercfg /h off, or Control Panel → Power → Choose what power buttons do), run `chkdsk X: /f`.
2. **vfat/FAT32 small files or old disk** — filesystem fine but size limits (file > 4 GB impossible). Fix: exFAT or NTFS.
3. **ext4 "read-only file system"**: `sudo dmesg | tail` for I/O errors; check SMART `sudo smartctl -a /dev/sdX`. A dying disk must not be reformatted — copy data first.
4. **Permissions**: dirs owned by root (`sudo chown -R $USER:$USER <dir>`).

## Identify the disk

```bash
lsblk -f
# FSTYPE shows current fs, MOUNTPOINT shows if mounted
sudo blkid /dev/sdXN          # exact type/UUID
```

## Unmount

```bash
umount /dev/sdXN               # if automounted under /run/media/...
udisksctl unmount -b /dev/sdXN # alternative
```

## Format

| Goal | Command | Notes |
| --- | --- | --- |
| Fedora data disk | `sudo mkfs.ext4 -F -L DATA /dev/sdXN` | recommended for plain storage |
| Fedora system-ish | `sudo mkfs.btrfs -f -L DATA /dev/sdXN` | snapshot/compression (Fedora root is btrfs) |
| NTFS (Windows compat) | `sudo mkfs.ntfs -f -L DATA /dev/sdXN` | needs `ntfs-3g` package |
| exFAT (USB, >4GB files, cross-platform) | `sudo mkfs.exfat -n DATA /dev/sdXN` | needs `exfatprogs` |
| FAT32 (small USB) | `sudo mkfs.fat -F 32 -n DATA /dev/sdXN` | file size limit 4 GB |

**Permission note**: `mkfs.ext4` without sudo fails with "Permission denied" — always run with sudo.

## Mount + ownership

```bash
sudo mkdir -p /home/$USER/DATA
sudo mount /dev/sdXN /home/$USER/DATA
sudo chown $USER:$USER /home/$USER/DATA
```


Do NOT pass `uid=`/`gid=` to `mount` for ext4 — ext4 rejects unknown options (`Unknown parameter 'uid'`). chown after mount instead. `uid=1000` belongs to FAT/exFAT mounts only.

## Auto-mount at boot (internal disks) — /etc/fstab

```bash
UUID=$(sudo blkid -s UUID -o value /dev/sdXN)
echo "UUID=$UUID /home/$USER/DATA ext4 defaults,noatime,nofail,x-systemd.device-timeout=10 0 2" | sudo tee -a /etc/fstab
```

- `nofail` + `x-systemd.device-timeout=10`: no boot hang if the disk is absent.
- Verify: `grep -v "^#" /etc/fstab | tail`, then `sudo systemctl daemon-reload`.

## Verify write

```bash
# Authorized verification only; this creates and removes test data.
mkdir -p /home/$USER/DATA/test && touch /home/$USER/DATA/test/file.txt && echo OK && rm -rf /home/$USER/DATA/test
lsblk -f /dev/sdX
```

## NTFS quirks after formatting

- ntfs-3g (FUSE) automounts via udisks2 under `/run/media/<user>/<UUID>`; if dirty flag set it mounts read-only — see "Why a disk can't be written to".
- `ntfsfix -n` is dry-run check; real fix is `ntfsfix` without `-n`.