How to Fix the Read-Only File System Error
With fsck, and when it could indicate a physically failing disk.
Your system switches to "read-only" (you can't save or modify anything) as an automatic protective measure when it detects a real problem on the disk — it isn't a whim, it's a safeguard.
1. Restart first
Sometimes this resolves the problem if it was caused by a one-off abrupt shutdown, with no real lasting damage.
2. Check the file system from a Live USB
sudo fsck -y /dev/sdXN
Replace with your actual partition. -y automatically
confirms the suggested repairs.
Warning: never run fsck on an actively mounted partition — boot from a Live USB so your main system's partition is unmounted during the repair.
3. If it persists: it could be the physical disk failing
Check the disk's SMART status:
sudo smartctl -a /dev/sdX
If reallocated or growing sector errors show up, the disk may be physically failing — prioritise backing up your data before continuing to attempt further repairs.
Frequently asked questions
Why does the system switch to read-only automatically?
It's a protective measure — upon detecting a real problem in the file system, Linux blocks writing to avoid damaging more data, until the problem is repaired.
Can I run fsck without booting from a Live USB?
Not on your active system's partition — fsck needs the partition to be unmounted to safely repair it, which is why it's recommended to do it from a Live USB.