jfs_tune(8)						  Set JFS file system parameters.					       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  exter-
	      nal-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 spe-
	      cial 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_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)