.\" Copyright (c) 2007 The DragonFly Project.  All rights reserved.
.\" 
.\" This code is derived from software contributed to The DragonFly Project
.\" by Matthew Dillon <dillon@backplane.com>
.\" 
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.\" $DragonFly: src/sbin/mount_hammer/mount_hammer.8,v 1.9.2.3 2008/08/04 20:14:42 thomas Exp $
.Dd June 24, 2008
.Dt MOUNT_HAMMER 8
.Os
.Sh NAME
.Nm mount_hammer
.Nd mount a HAMMER file system
.Sh SYNOPSIS
.Nm
.Op Fl o Ar options
.Op Fl T Ar transaction-id
.Ar special ...
.Ar node
.Nm
.Op Fl o Ar options
.Op Fl T Ar transaction-id
.Ar special[:special]*
.Ar node
.Nm
.Op Fl u
.Op Fl o Ar options
.Ar node
.Sh DESCRIPTION
The
.Nm
utility mounts a
.Nm HAMMER
file system backed by
.Ar special
file(s) at mount point
.Ar node .
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl o Ar options
Specify mount options, which are a comma delimited set of options (see
.Xr mount 8 ) .
Supported mount options are:
.Bl -tag -width indent
.It Ar ro
Issue a read-only mount.
.It Ar 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.
.It Ar 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
.Nm HAMMER
mounts making up the fail-over group.
.It Ar nomirror
By default a
.Nm 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.
.El
.It Fl T Ar transaction-id
Mount the file system as-of a particular
transaction id.
The mount will automatically be made read-only.
The
.Ar transaction-id
must be specified as a 64 bit hex value prefixed with "0x".
.It Fl u
Update the mount point.  This is typically used to upgrade a mount to
read-write or downgrade it to read-only.
.El
.Sh 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.
.Sh EXAMPLES
Mount a
.Nm HAMMER
file system made up of two volumes onto
.Pa /mnt :
.Bd -literal -offset indent
mount_hammer -o ro,noatime /dev/ad0s1d /dev/ad1s1d /mnt
.Ed
.Pp
A corresponding
.Xr fstab 5
entry is:
.Bd -literal -offset indent
/dev/ad0s1d:/dev/ad1s1d /mnt hammer ro,noatime
.Ed
.Sh DIAGNOSTICS
Exit status is 0 on success and 1 on error.
.Sh SEE ALSO
.Xr mount 2 ,
.Xr unmount 2 ,
.Xr fstab 5 ,
.Xr HAMMER 5 ,
.Xr disklabel 8 ,
.Xr disklabel64 8 ,
.Xr fdisk 8 ,
.Xr gpt 8 ,
.Xr hammer 8 ,
.Xr mount 8 ,
.Xr newfs_hammer 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Dx 1.11 .
.Sh AUTHORS
.An Matthew Dillon Aq dillon@backplane.com