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)