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GJOURNAL(8)             FreeBSD System Manager's Manual            GJOURNAL(8)

NAME
     gjournal - control utility for journaled devices

SYNOPSIS
     gjournal label [-cfhv] [-s jsize] dataprov [jprov]
     gjournal stop [-fv] name ...
     gjournal sync [-v]
     gjournal clear [-v] prov ...
     gjournal dump prov ...
     gjournal list
     gjournal status
     gjournal load
     gjournal unload

DESCRIPTION
     The gjournal utility is used for journal configuration on the given GEOM
     provider.  The Journal and data may be stored on the same provider or on
     two separate providers.  This is block level journaling, not file system
     level journaling, which means everything gets logged, e.g. for file
     systems, it journals both data and metadata.  The gjournal GEOM class can
     talk to file systems, which allows the use of gjournal for file system
     journaling and to keep file systems in a consistent state.  At this time,
     only UFS file system is supported.

     To configure journaling on the UFS file system using gjournal, one should
     first create a gjournal provider using the gjournal utility, then run
     newfs(8) or tunefs(8) on it with the -J flag which instructs UFS to
     cooperate with the gjournal provider below.  There are important
     differences in how journaled UFS works.  The most important one is that
     sync(2) and fsync(2) system calls do not work as expected anymore.  To
     ensure that data is stored on the data provider, the gjournal sync
     command should be used after calling sync(2).  For the best performance
     possible, soft-updates should be disabled when gjournal is used.  It is
     also safe and recommended to use the async mount(8) option.

     When gjournal is configured on top of gmirror(8) or graid3(8) providers,
     it also keeps them in a consistent state, thus automatic synchronization
     on power failure or system crash may be disabled on those providers.

     The gjournal utility uses on-disk metadata, stored in the provider's last
     sector, to store all needed information.  This could be a problem when an
     existing file system is converted to use gjournal.

     The first argument to gjournal indicates an action to be performed:

     label       Configures gjournal on the given provider(s).  If only one
                 provider is given, both data and journal are stored on the
                 same provider.  If two providers are given, the first one
                 will be used as data provider and the second will be used as
                 the journal provider.

                 Additional options include:

                 -c              Checksum journal records.

                 -f              May be used to convert an existing file
                                 system to use gjournal, but only if the
                                 journal will be configured on a separate
                                 provider and if the last sector in the data
                                 provider is not used by the existing file
                                 system.  If gjournal detects that the last
                                 sector is used, it will refuse to overwrite
                                 it and return an error.  This behavior may be
                                 forced by using the -f flag, which will force
                                 gjournal to overwrite the last sector.

                 -h              Hardcode provider names in metadata.

                 -s jsize        Specifies size of the journal if only one
                                 provider is used for both data and journal.
                                 The default is one gigabyte.  Size should be
                                 chosen based on provider's load, and not on
                                 its size.  It is not recommended to use
                                 gjournal for small file systems (e.g.: only
                                 few gigabytes big).

     clear       Clear metadata on the given providers.

     stop        Stop the given provider.

                 Additional options include:

                 -f     Stop the given provider even if it is opened.

     sync        Trigger journal switch and enforce sending data to the data
                 provider.

     dump        Dump metadata stored on the given providers.

     list        See geom(8).

     status      See geom(8).

     load        See geom(8).

     unload      See geom(8).

     Additional options include:

     -v     Be more verbose.

EXIT STATUS
     Exit status is 0 on success, and 1 if the command fails.

EXAMPLES
     Create a gjournal based UFS file system and mount it:

           gjournal load
           gjournal label da0
           newfs -J /dev/da0.journal
           mount -o async /dev/da0.journal /mnt

     Configure journaling on an existing file system, but only if gjournal
     allows this (i.e., if the last sector is not already used by the file
     system):

           umount /dev/da0s1d
           gjournal label da0s1d da0s1e && \
               tunefs -J enable -n disable da01sd.journal && \
               mount -o async /dev/da0s1d.journal /mnt || \
               mount /dev/da0s1d /mnt

SEE ALSO
     geom(4), geom(8), mount(8), newfs(8), tunefs(8), umount(8)

HISTORY
     The gjournal utility appeared in FreeBSD 7.0.

AUTHORS
     Pawel Jakub Dawidek <pjd@FreeBSD.org>

BUGS
     Documentation for sysctls kern.geom.journal.* is missing.

FreeBSD 11.0-PRERELEASE         April 13, 2008         FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | EXIT STATUS | EXAMPLES | SEE ALSO | HISTORY | AUTHORS | BUGS

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