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GROWFS(8)               FreeBSD System Manager's Manual              GROWFS(8)

     growfs - grow size of an existing ufs file system

     growfs [-Ny] [-s size] special

     The growfs utility extends the newfs(8) program.  Before starting growfs
     the disk must be labeled to a bigger size using bsdlabel(8).  If you wish
     to grow a file system beyond the boundary of the slice it resides in, you
     must re-size the slice using fdisk(8) before running growfs.  If you are
     using volumes you must enlarge them by using vinum(8).  The growfs
     utility extends the size of the file system on the specified special
     file.  Currently growfs can only enlarge unmounted file systems.  Do not
     try enlarging a mounted file system, your system may panic and you will
     not be able to use the file system any longer.  Most of the newfs(8)
     options cannot be changed by growfs.  In fact, you can only increase the
     size of the file system.  Use tunefs(8) for other changes.

     The following options are available:

     -N      ``Test mode''.  Causes the new file system parameters to be
             printed out without actually enlarging the file system.

     -y      ``Expert mode''.  Usually growfs will ask you if you took a
             backup of your data before and will do some tests whether special
             is currently mounted or whether there are any active snapshots on
             the file system specified.  This will be suppressed.  So use this
             option with great care!

     -s size
             Determines the size of the file system after enlarging in
             sectors.  This value defaults to the size of the raw partition
             specified in special (in other words, growfs will enlarge the
             file system to the size of the entire partition).

           growfs -s 4194304 /dev/vinum/testvol

     will enlarge /dev/vinum/testvol up to 2GB if there is enough space in

     bsdlabel(8), dumpfs(8), fdisk(8), ffsinfo(8), fsck(8), newfs(8),
     tunefs(8), vinum(8)

     The growfs utility first appeared in FreeBSD 4.4.

     Christoph Herrmann <>
     Thomas-Henning von Kamptz <>
     The GROWFS team <growfs@Tomsoft.COM>

     The growfs utility works starting with FreeBSD 3.x.  There may be cases
     on FreeBSD 3.x only, when growfs does not recognize properly whether or
     not the file system is mounted and exits with an error message.  Then
     please use growfs -y if you are sure that the file system is not mounted.
     It is also recommended to always use fsck(8) after enlarging (just to be
     on the safe side).

     For enlarging beyond certain limits, it is essential to have some free
     blocks available in the first cylinder group.  If that space is not
     available in the first cylinder group, a critical data structure has to
     be relocated into one of the new available cylinder groups.  On FreeBSD
     3.x this will cause problems with fsck(8) afterwards.  So fsck(8) needs
     to be patched if you want to use growfs for FreeBSD 3.x.  This patch is
     already integrated in FreeBSD starting with FreeBSD 4.4.  To avoid an
     unexpected relocation of that structure it is possible to use ffsinfo -g
     0 -l 4 on the first cylinder group to verify that nbfree in the CYLINDER
     SUMMARY (internal cs) of the CYLINDER GROUP cgr0 has enough blocks.  As a
     rule of thumb for default file system parameters one block is needed for
     every 2 GB of total file system size.

     Normally growfs writes this critical structure to disk and reads it again
     later for doing more updates.  This read operation will provide
     unexpected data when using -N.  Therefore, this part cannot really be
     simulated and will be skipped in test mode.

FreeBSD 11.0-PRERELEASE        September 8, 2000       FreeBSD 11.0-PRERELEASE


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