TUNEFS(8)               COMMAND REFERENCE               TUNEFS(8)



NAME
     tunefs - tune up an existing file system

SYNOPSIS
     /etc/tunefs tuneup-options special | filesystem

DESCRIPTION
     Tunefs is designed to change the dynamic parameters of a
     file system which affect the layout policies.  The
     parameters which are to be changed are indicated by the
     options given below.

     The file system may be specified by giving special, the name
     of the special file (device) on which the file system is
     mounted, or by specifying filesystem, the name of the root
     directory of the file system.

OPTIONS
     Tuneup options are:

     -a maxcontig
         This specifies the maximum number of contiguous blocks
         that will be laid out before forcing a rotational delay
         (see -d below).  The default value is one, since most
         device drivers require an interrupt per disk transfer.
         Device drivers that can chain several buffers together
         in a single transfer should set this to the maximum
         chain length.

     -d rotdelay
         This specifies the expected time (in milliseconds) to
         service a transfer completion interrupt and initiate a
         new transfer on the same disk.  It is used to decide how
         much rotational spacing to place between successive
         blocks in a file.

     -e maxbpg
         This indicates the maximum number of blocks any single
         file can allocate out of a cylinder group before it is
         forced to begin allocating blocks from another cylinder
         group.  Typically this value is set to about one quarter
         of the total blocks in a cylinder group.  The intent is
         to prevent any single file from using up all the blocks
         in a single cylinder group, thus degrading access times
         for all files subsequently allocated in that cylinder
         group.  The effect of this limit is to cause big files
         to do long seeks more frequently than if they were
         allowed to allocate all the blocks in a cylinder group
         before seeking elsewhere.  For file systems with
         exclusively large files, this parameter should be set
         higher.




Printed 10/17/86                                                1

TUNEFS(8)               COMMAND REFERENCE               TUNEFS(8)



     -m minfree
         This value specifies the percentage of space held back
         from normal users; the minimum free space threshold.
         The default value used is 10%.  This value can be set to
         zero, however up to a factor of three in throughput will
         be lost over the performance obtained at a 10%
         threshold.  Note that if the value is raised above the
         current usage level, users will be unable to allocate
         files until enough files have been deleted to get under
         the higher threshold.

RETURN VALUE
     [NO_ERRS]      Command completed without error.

     [NP_ERR]       An error occurred that was not a system
                    error.  Execution terminated.

     [P_ERR]        A system error occurred. Execution
                    terminated.  See intro(2) for more
                    information on system errors.

CAVEATS
     This program should work on mounted and active file systems.
     Because the super-block is not kept in the buffer cache, the
     program will only take effect if it is run on dismounted
     file systems.  (If run on the root file system, the system
     must be rebooted.)

SEE ALSO
     fs(5), newfs(8), mkfs(8).

























Printed 10/17/86                                                2

%%index%%
na:72,76;
sy:148,237;
de:385,582;
op:967,1801;2912,580;
rv:3492,417;
ca:3909,333;
se:4242,132;
%%index%%000000000128