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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
              (Experimental) 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 com-
              mand

              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=vol-
              ume_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 parti-
       tion 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://oss.software.ibm.com/jfs

       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  (barndtATus.com)

       jfs_tune is maintained by IBM.
       See the JFS project web site for more details:
       http://oss.software.ibm.com/jfs/



                               October 28, 2002                    jfs_tune(8)