LL: My External Hard Drive Is Suddenly Read Only In Linux

First logical thing to check, are other files besides my Insecure Hippo Power Point presentation also read only?

No.  I can read those.  That’s definitely a good thing.

Permissions are set to read and write.  I don’t know why it’s coming up as read only.

. Filesystem Remounted Read-Only Due to Errors:
  • The most common reason is that the filesystem containing the file has been automatically remounted in read-only mode by the kernel due to detected errors (e.g., I/O errors, corruption). This is a protective measure to prevent further data corruption.
  • Check: Examine the kernel logs using dmesg or journalctl -k for messages indicating disk errors or read-only remounts.
  • Solution: If errors are found, back up critical data immediately. Then, you might need to reboot and run a filesystem check (e.g., fsck /dev/sdXn) or consider replacing a failing storage device.
2. Immutable File Attribute:
  • The file might have the immutable attribute set, which prevents even root from modifying or deleting it.
  • Check: Use lsattr <filename> to check for the ‘i’ flag.
  • Solution: Remove the immutable attribute with sudo chattr -i <filename>.
3. Read-Only Mount Point:
  • The directory where the file resides, or an ancestor directory, might be mounted as read-only.
  • Check: Use mount to list all mounted filesystems and their options. Look for ro (read-only) next to the relevant mount point.
  • Solution: Remount the filesystem with read-write permissions if appropriate (e.g., sudo mount -o remount,rw /path/to/mountpoint).
4. Symbolic Links and Filesystem Boundaries:
  • If the file is a symbolic link, its target might reside on a different filesystem that is indeed read-only, or the link itself might point to a location on a read-only filesystem.
  • Check: Use ls -l <filename> to identify if it’s a symbolic link and its target. You can also use namei <filename> to trace the path and identify any symbolic links.
5. Application-Specific Locks or Behaviors:
  • Certain applications (e.g., text editors like Vim if configured to do so) might enforce their own read-only behavior or create lock files that prevent modification.
  • Check: Review the application’s configuration or documentation.
Troubleshooting Steps:
  • Check Kernel Logs: dmesg | grep -i "error\|read-only" or journalctl -k | grep -i "error\|read-only"
  • Verify Mount Options: mount
  • Check Immutable Attribute: lsattr <filename>
  • Inspect Permissions: ls -l <filename> and ls -ld <directory_containing_file>
  • Examine Symbolic Links (if applicable): ls -l <filename> and namei <filename>
Addressing the underlying cause identified by these checks is crucial for resolving the “read-only” issue.
I sorted this out by opening the file on my desktop.

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