---
name: "jfs_tune"
section: "8"
platform: "linux"
package: "jfsutils"
version: "1.1.15-9"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/jfs_tune"
---

# jfs\_tune(8)

adjust tunable file system parameters on JFS

## NAME

**jfs\_tune** - adjust tunable file system parameters on JFS

## SYNOPSIS

**jfs\_tune** \[options\] *device*

## DESCRIPTION

**jfs\_tune** adjusts tunable parameters on a Linux JFS file system or external journal. **jfs\_tune** must be run as root.

*device* is the special file name corresponding to the actual device (e.g. */dev/hdb1*) on which a JFS file system or JFS external journal has been created.

## OPTIONS

- **-J device=***external-journal*

  Attach the JFS external journal located on *external-journal* to the JFS file system on *device*.

-

  The external journal must already have been created using the command. More than one file system may share the same external journal.

-

  **mkfs.jfs -J journal\_dev** *external-journal*

-

  Attach the external journal to the file system by using the command

-

  **jfs\_tune -J device=***external-journal* *device*

-

  Instead of specifying a device name directly, *external-journal* can also be specified by either **LABEL=***label* or **UUID=***UUID* (Use **jfs\_tune -l** *device* to display a journal device's volume label and UUID.)

- **-l**

  List the contents of the JFS file system or external journal superblock that resides on *device*.

- **-L** *volume-label*

  Set the volume label of the JFS file system or external journal. JFS labels can be at most 16 characters long; if *volume-label* is longer than 16 characters, **jfs\_tune** will truncate it and print a warning.  The volume label can be used by [**mount**(8)](/mount/8.md), [**fsck**(8)](/fsck/8.md), and **/etc/fstab**(5) (and possibly others) by specifying **LABEL=***volume\_label* instead of a block special device name like **/dev/hda5**.

- **-U** *UUID*

  Set the universally unique identifier (UUID) of the file system or external journal device to *UUID*. The format of the UUID is a series of hex digits separated by hyphens, like this: "c1b9d5a2-f162-11cf-9ece-0020afc76f16". The *UUID* parameter may also be one of the following:

  - *clear*

    clear the file system UUID

  - *random*

    generate a new randomly-generated UUID

  - *time*

    generate a new time-based UUID

-

  The UUID may be used by [**mount**(8)](/mount/8.md), [**fsck**(8)](/fsck/8.md), and **/etc/fstab**(5) (and possibly others) by specifying **UUID=***uuid* instead of a block special device name like **/dev/hda1**.

-

  See **uuidgen**(8) for more information.

- **-V**

  Print version information and exit (regardless of any other chosen options).

## EXAMPLES

Set a randomly-generated UUID for the JFS file system on the 3rd partition of the 2nd hard disk, and view the resultant superblock:

-

  **jfs\_tune -l -U random /dev/hdb3**

-

  Attach an already existing external journal on a device labeled JFSLog to a JFS file system on /dev/hda8:

-

  **jfs\_tune -J device=LABEL=JFSLog /dev/hda8**

-

  ## REPORTING BUGS

If you find a bug in **JFS** or **jfs\_tune**, please report it via the bug tracking system ("Report Bugs" section) of the JFS project web site:

```
http://jfs.sourceforge.net/
```

Please send as much pertinent information as possible including any error messages resulting from running **jfs\_tune**.

## SEE ALSO

[**jfs\_fsck**(8)](/jfs_fsck/8.md)**,** [**jfs\_mkfs**(8)](/jfs_mkfs/8.md)**,** [**jfs\_fscklog**(8)](/jfs_fscklog/8.md)**,** [**jfs\_logdump**(8)](/jfs_logdump/8.md)**,** [**jfs\_debugfs**(8)](/jfs_debugfs/8.md)

## AUTHOR

```
Barry Arndt  (barndt@us.ibm.com)
```

**jfs\_tune** is maintained by IBM.

```
See the JFS project web site for more details:
http://jfs.sourceforge.net/
```