jfs_tune(8)

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

Only supported on JFS versions (1.0.18 or later) that support external journal. Attach the JFS external journal located on external-journal to the JFS file system on device.

Currently, you may only attach a single JFS file system device to a single JFS external journal (i.e. each JFS file system using an external journal must have a unique external journal).

The external journal must already have been created using the command

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), fsck(8), 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), fsck(8), 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 cho

sen 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_mkfs(8), jfs_fscklog(8), jfs_logdump(8), jfs_debugfs(8)

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/

October 28, 2002 jfs_tune(8)