cmpress(1M)      SYSTEM ADMINISTRATION COMMANDS       cmpress(1M)



NAME
     cmpress - re-link file system to remove fragmentation

SYNOPSIS
     /usr/sbin/cmpress

DESCRIPTION
     cmpress re-links the input file  system  to  improve  access
     time  by  cleaning  up fragmentation of files throughout the
     file system. The file system must be mounted  in  order  for
     this  procedure  to  find  the file system and determine its
     characteristics.

     cmpress uses a 3B2 Computer cartridge tape for  intermediate
     storage.  The file system is first copied onto the tape, the
     old file system is removed and the free block list is sorted
     into  sequential  order, then the file system is copied back
     onto the disk so that file  system  blocks  that  previously
     were  scattered throughout the file system are in contiguous
     space.

     Notice that the file system is destroyed during the  process
     of  compressing  it.   For this reason it is strongly recom-
     mended that an up-to-date backup of the file system be  made
     before  the  file  system  is compressed.  In the event of a
     mishap during file system compression the file system  could
     be restored from the backup.

     Since the file system is destroyed  during  the  compression
     process,  it  is not possible to compress the root file sys-
     tem.  The cmpress command will reject the file system name /
     if it is entered.

     Compressing any file system except /usr can be done  through
     the  sysadm  command.  An example of such a file compression
     is given below.  Compressing the /usr file system  is  some-
     what  more  complex  a  process, since the sysadm facilities
     reside in the /usr file system.  A  scheme  for  compressing
     /usr is given in the examples.

EXAMPLES
     To compress a file system named applic, the  following  com-
     mand would be issued:

                           sysadm  tapemgmt

     When the  tape  management  facilities  menu  is  displayed,
     select  the compress facility and answer the questions posed
     by the shell procedure.  This compress facility invokes  the
     /usr/sbin/cmpress procedure.





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cmpress(1M)      SYSTEM ADMINISTRATION COMMANDS       cmpress(1M)



     To compress the /usr file system the UNIX system has  to  be
     in  single user mode with the /usr file system mounted.  The
     following sequence of commands will  take  the  system  from
     multiuser  to  single user mode, compress the /usr file sys-
     tem, then return the system to multiuser mode.  Notice  that
     any  work going on in the system at the time that the system
     is changed to single user mode will be terminated,  so  this
     process  should  be  done  at a time when there are no other
     users logged in, and no background tasks are being done.  It
     should be done only from the console from the root login.
     First check to see how /usr is mounted.

          mount

     Make note of the /dev/dsk/c?d?s? information,  as  you  will
     need it later.

     Now take the system down to single user mode.

          init 1

     Lots of messages will now appear, and you will need  to  log
     back in as root.

     Now mount the /usr file  system.   Use  the  /dev/dsk/c?d?s?
     information from the mount command above.

          mount  /dev/dsk/c?d?s?  /usr

     Now compress the file system

          /usr/sbin/cmpress /dev/rSA/ctape?

     The procedure will pose  a  series  of  questions.   As  the
     compression  process  runs  it will display a series of mes-
     sages indicating its progress.

     When compression is complete  the  following  commands  will
     unmount  the /usr file system and return the system to multi
     user mode.  Many messages will be displayed during this pro-
     cess.

          umount  /dev/dsk/c1d0s2
          init 2

SEE ALSO
     sysadm(1M)

DIAGNOSTICS
     The diagnostic messages are intended to be self explanatory.





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cmpress(1M)      SYSTEM ADMINISTRATION COMMANDS       cmpress(1M)



NOTES
     As mentioned above, since the compression of the file system
     entails  its  destruction  and  restoration  it  is strongly
     recommended that a backup copy of the file  system  be  made
     before its compression is attempted.


















































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