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MOUNT_HAMMER(8)        DragonFly System Manager's Manual       MOUNT_HAMMER(8)


mount_hammer -- mount a HAMMER file system


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


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.


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.


The mount_hammer utility exits 0 on success, and >0 if an error occurs.


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


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


The mount_hammer utility first appeared in DragonFly 1.11.


Matthew Dillon <dillon@backplane.com> DragonFly 4.3 December 31, 2015 DragonFly 4.3

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