---
name: "gjournal"
section: "8"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/gjournal"
---

# gjournal(8)

control utility for journaled devices

## 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** \[**--libxo**\] **list**

**gjournal** \[**--libxo**\] **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)](/newfs/8.md) or [tunefs(8)](/tunefs/8.md) 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)](/sync/2.md) and [fsync(2)](/fsync/2.md) 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)](/sync/2.md). 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)](/mount/8.md) option.

When **gjournal** is configured on top of [gmirror(8)](/gmirror/8.md) or [graid3(8)](/graid3/8.md) 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; recommended minimum is twice the size of the physical memory installed. 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)](/geom/8.md).

- **status**

  See [geom(8)](/geom/8.md).

- **load**

  See [geom(8)](/geom/8.md).

- **unload**

  See [geom(8)](/geom/8.md).

- **--libxo**

  Generate output via [libxo(3)](/libxo/3.md) in a selection of different human and machine readable formats. See [xo\_options(7)](/xo_options/7.md) for details on command line arguments.

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 da0s1d.journal && \
    mount -o async /dev/da0s1d.journal /mnt || \
    mount /dev/da0s1d /mnt
```

## SYSCTLS

Gjournal adds the sysctl level kern.geom.journal. The string and integer information available is detailed below. The changeable column shows whether a process with appropriate privilege may change the value.

| | | |
| --- | --- | --- |
| **sysctl name** | Type | Changeable |
| debug | integer | yes |
| switch\_time | integer | yes |
| force\_switch | integer | yes |
| parallel\_flushes | integer | yes |
| accept\_immediately | integer | yes |
| parallel\_copies | integer | yes |
| record\_entries | integer | yes |
| optimize | integer | yes |

- debug

  Setting a non-zero value enables debugging at various levels. Debug level 1 will record actions at a journal level, relating to journal switches, metadata updates, etc. Debug level 2 will record actions at a higher level, relating to the numbers of entries in journals, access requests, etc. Debug level 3 will record verbose detail, including insertion of I/Os to the journal.

- switch\_time

  The maximum number of seconds a journal is allowed to remain open before switching to a new journal.

- force\_switch

  Force a journal switch when the journal uses more than N% of the free journal space.

- parallel\_flushes

  The number of flush I/O requests to be sent in parallel when flushing the journal to the data provider.

- accept\_immediately

  The maximum number of I/O requests accepted at the same time.

- parallel\_copies

  The number of copy I/O requests to send in parallel.

- record\_entries

  The maximum number of record entries to allow in a single journal.

- optimize

  Controls whether entries in a journal will be optimized by combining overlapping I/Os into a single I/O and reordering the entries in a journal. This can be disabled by setting the sysctl to 0.

### cache

The string and integer information available for the cache level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value.

| | | |
| --- | --- | --- |
| **sysctl name** | Type | Changeable |
| used | integer | no |
| limit | integer | yes |
| divisor | integer | no |
| switch | integer | yes |
| misses | integer | yes |
| alloc\_failures | integer | yes |

- used

  The number of bytes currently allocated to the cache.

- limit

  The maximum number of bytes to be allocated to the cache.

- divisor

  Sets the cache size to be used as a proportion of kmem\_size. A value of 2 (the default) will cause the cache size to be set to 1/2 of the kmem\_size.

- switch

  Force a journal switch when this percentage of cache has been used.

- misses

  The number of cache misses, when data has been read, but was not found in the cache.

- alloc\_failures

  The number of times memory failed to be allocated to the cache because the cache limit was hit.

### stats

The string and integer information available for the statistics level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value.

| | | |
| --- | --- | --- |
| **sysctl name** | Type | Changeable |
| skipped\_bytes | integer | yes |
| combined\_ios | integer | yes |
| switches | integer | yes |
| wait\_for\_copy | integer | yes |
| journal\_full | integer | yes |
| low\_mem | integer | yes |

- skipped\_bytes

  The number of bytes skipped.

- combined\_ios

  The number of I/Os which were combined by journal optimization.

- switches

  The number of journal switches.

- wait\_for\_copy

  The number of times the journal switch process had to wait for the previous journal copy to complete.

- journal\_full

  The number of times the journal was almost full, forcing a journal switch.

- low\_mem

  The number of times the low\_mem hook was called.

## SEE ALSO

[geom(4)](/geom/4.md), [xo\_options(7)](/xo_options/7.md), [geom(8)](/geom/8.md), [mount(8)](/mount/8.md), [newfs(8)](/newfs/8.md), [tunefs(8)](/tunefs/8.md), [umount(8)](/umount/8.md)

## HISTORY

The **gjournal** utility appeared in FreeBSD 7.0.

## AUTHORS

Pawel Jakub Dawidek ⟨*pjd@FreeBSD.org*⟩