What is called Journalling in Linux operating system ?

Correct answer: File saving as transaction

Definition: Journalling is a file system technique where changes are first written to a journal (a log) as transactions and then applied to the main file system. Recording changes in the journal ensures that the file system can be brought back to a consistent state after a crash by replaying or discarding incomplete transactions.

• Why it is used: Ensures file system consistency and reduces the need for long file system checks after an unexpected shutdown.

• How it works: Changes are logged to the journal first; once the journal entry is safely written, the changes are applied to the file system. On recovery, the system replays the journal to complete or roll back transactions.

• Trade-offs: There is a small write overhead due to journalling, but this is often acceptable given the improved reliability and faster recovery.

• Common journalling file systems: ext3, ext4, XFS, JFS.

Why the other choices are incorrect:

• "Process scheduling" refers to allocating CPU time to processes and is unrelated to logging file system changes.

• "A type of thread" is incorrect because threads are execution units; journalling describes a logging mechanism for file systems, not a thread type.

• "An editor" is a program for editing text and is unrelated to file system journalling.