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), 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 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)