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 4/6/89                                                  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), and mkfs(8).
























Printed 4/6/89                                                  2

%%index%%
na:288,92;
sy:380,313;
de:693,650;
op:1343,2056;3759,658;
rv:4417,461;
ca:4878,361;
se:5239,163;
%%index%%000000000130