fsfreeze

fsfreeze [options]

--freeze
    Freeze the filesystem at the specified mount point.

--unfreeze
    Unfreeze a previously frozen filesystem at the specified mount point.

--help
    Display help text and exit.

--version
    Display version information and exit.


    The mount point of the filesystem to freeze or unfreeze.

The fsfreeze command suspends access to a filesystem, ensuring data consistency during backups or other operations. It halts all new I/O operations to the specified filesystem until it is thawed. This prevents data corruption or inconsistencies during backup processes. It is important to note that processes already having open files on the frozen filesystem are not blocked, but further attempts to read or write to that filesystem will be blocked until the filesystem is thawed. The fsfreeze command supports various filesystems, including ext4, XFS, and others. Using fsfreeze requires root privileges or capabilities allowing to freeze a filesystem. After freezing the filesystem, it can be thawed using the --unfreeze option. Failures can occur if the filesystem is already frozen or if there are errors during the freeze/unfreeze process. Care must be taken to ensure the filesystem is thawed after the backup to restore normal operation. Incorrectly using fsfreeze can lead to system instability or data loss if not handled carefully.
fsfreeze provides a crucial functionality for creating consistent filesystem snapshots.

Using fsfreeze without unfreezing the filesystem afterwards can cause the system to become unresponsive as processes might hang waiting for I/O to complete. Ensure the filesystem is unfreezed after the backup.

If fsfreeze encounters an error, it will usually return a non-zero exit code. Check the return code of the command to detect failures, and examine system logs for more detailed error messages. For example, if a process is heavily utilizing the filesystem, freezing might take longer or fail. Be aware of situations where a filesystem is busy and the freezing action times out or fails altogether.

While fsfreeze is designed to work with various filesystems (e.g., ext4, XFS), support may vary depending on the kernel version and the specific filesystem implementation. Consult the filesystem's documentation to confirm that it supports freezing capabilities and understand any filesystem-specific considerations when using fsfreeze.

The fsfreeze command was introduced to provide a reliable way to create consistent filesystem snapshots, primarily for backup purposes. Over time it has become a standard tool for ensuring data integrity during critical operations requiring quiesced filesystems.

mount(8), umount(8)