block-device-read-only · shipping · also Block-device read-only state

Linux block-device read-only flag

The Linux block-device read-only flag is a software-controlled device state exposed through block-device ioctls to restrict write access.

The util-linux v2.41.1 manual warns that changing the flag may leave existing active access unaffected, including a filesystem already in read-write use. [1] A flag value alone is not evidence of a validated forensic write-blocking workflow; NIST publishes software write-blocker test resources, so software and unvalidated are not synonyms. [3]

Relations

related

read-only-mount, btrfs-read-only-subvolume

Limitations

• Device state, filesystem state and subvolume properties have distinct scopes. [1, 2]

Citations

1. util-linux v2.41.1: blockdev(8), read-only flag and active-access caveat (accessed 2026-10-15)
2. util-linux v2.41.1: mount(8), Read-only Setting Notes (accessed 2026-10-15)
3. NIST CFTT: Software Write Block testing resources (accessed 2026-10-15)
4. Hesela: Btrfs tree logs and read-only scope boundaries (accessed 2026-10-15)

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