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gjournal (8)
>> gjournal (8) ( FreeBSD man: Команды системного администрирования )
BSD mandoc
NAME
gjournal
- control utility for journaled devices
SYNOPSIS
label
[-cfhv
]
[-s jsize
]
dataprov
[jprov
]
stop
[-fv
]
name ... sync
[-v
]
clear
[-v
]
prov ... dumpprov ... list status load unload
DESCRIPTION
The
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
GEOM class can talk to file systems, which allows the use of
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
,
one should first create a
provider using the
utility, then run
newfs(8)
or
tunefs(8)
on it with the
-J
flag which instructs UFS to cooperate with the
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
sync
command should be used after calling
sync(2).
For the best performance possible, soft-updates should be disabled when
is used.
It is also safe and recommended to use the
asyncmount(8)
option.
When
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
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
.
The first argument to
indicates an action to be performed:
label
Configures
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
,
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
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
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
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.
