MOUNT_HAMMER(8)

NAME
mount_hammer - mount a HAMMER file system

SYNOPSIS
mount_hammer [-o options] [-T transaction-id] special ... node
mount_hammer [-o options] [-T transaction-id] special[:special]* node
mount_hammer -u [-o options] node

DESCRIPTION
The mount_hammer utility mounts a HAMMER file system backed by special file(s) at mount point node.

The options are as follows:

-o options
    Options are specified with a -o flag followed by a comma separated string of options. See the mount(8) man page for possible options and their meanings. The following HAMMER specific options are also available:

    nohistory
        Put the entire file system in no-history mode. Change history is not retained. Use of this option may increase the overhead of doing mirroring. This option is generally only used in an emergency.

    master=id
        Assign a master id for the entire mount which applies to all PFSs under the mount. This is intended to help support multi-master and fail-over operation. Multi-master operation is not yet supported. If you intend to upgrade slaves to masters and downgrade masters to slaves as part of a fail-over setup, it's a good idea to assign a different master id to the HAMMER mounts making up the fail-over group.

    nomirror
        By default a HAMMER mount assigns a master id of 0. You can force no-mirror operation by specifying this option. This option disables mirror transaction id propagation in the B-Tree and will improve write performance somewhat but also prevents incremental mirroring from working at all, and is not recommended.

-T transaction-id
    Mount the file system as-of a particular transaction id. The mount will automatically be made read-only. The transaction-id must be specified as a 64 bit hex value prefixed with "0x".

-u  Update the mount point. This is typically used to upgrade a mount to read-write or downgrade it to read-only.

NOTES
Note that issuing a read-only mount which requires UNDOs to be run will still run the UNDOs, but will not flush the buffer cache buffers until/if the mount is updated to read-write.

EXIT STATUS

EXAMPLES
Mount a HAMMER file system made up of two volumes onto /mnt:

    mount_hammer -o ro,noatime /dev/ad0s1d /dev/ad1s1d /mnt

Above is equivalent to below using blkdevs format for HAMMER volumes as mount_hammer supports both formats.

    mount_hammer -o ro,noatime /dev/ad0s1d:/dev/ad1s1d /mnt

A corresponding fstab(5) entry is:

    /dev/ad0s1d:/dev/ad1s1d /mnt hammer ro,noatime

SEE ALSO
mount(2), unmount(2), fstab(5), HAMMER(5), disklabel(8), disklabel64(8), fdisk(8), gpt(8), hammer(8), mount(8), newfs_hammer(8)

HISTORY
The mount_hammer utility first appeared in DragonFly 1.11.

AUTHORS
Matthew Dillon <dillon@backplane.com>