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NetBSD 6.1.5 - man page for resize_ffs (netbsd section 8)

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RESIZE_FFS(8)			   BSD System Manager's Manual			    RESIZE_FFS(8)

NAME
     resize_ffs -- resize a file system on disk or in a file

SYNOPSIS
     resize_ffs [-y] [-s size] special

DESCRIPTION
     resize_ffs resizes a file system.	special is the name of the raw disk device or file where
     the file system resides.  resize_ffs can both grow and shrink file systems.  When growing,
     the disk device must of course be large enough to contain the new file system; resize_ffs
     simply extends the file system data structures into the new space.  When shrinking,
     resize_ffs assumes this.  resize_ffs has to copy anything that currently resides in the
     space being shrunk away; there must be enough space free on the file system for this to suc-
     ceed.  If there isn't, resize_ffs will complain and exit; when this happens, it attempts to
     always leave the file system in a consistent state, but it is probably a good idea to check
     the file system with fsck(8).

     If no -s option is provided, resize_ffs will grow the file system to the underlying device
     size which is determined from special.

     The options are as follows:

     -s      Specify the file system size to which the file system should be resized.  The size
	     is given as the count of disk sectors, usually 512 bytes.	It will not work cor-
	     rectly for file systems with other sector sizes.  To see the exact value, have a
	     look at the disk specification or the disklabel.  Mostly used to shrink file sys-
	     tems.

     -y      Disable sanity questions made by resize_ffs.

WARNING
     Interrupting resize_ffs may leave your file system in an inconsistent state and require a
     restore from backup. It attempts to write in the proper order to avoid problems, but as it
     is still considered experimental, you should take great care when using it.

     When resize_ffs is applied to a consistent file system, it should always produce a consis-
     tent file system; if the file system is not consistent to start with, resize_ffs may misbe-
     have, anything from dumping core to completely curdling the data.	It's probably wise to
     fsck(8) the file system before and after, just to be safe.  You should be aware that just
     because fsck(8) is happy with the file system does not mean it is intact.

EXIT STATUS
     resize_ffs exits with 0 on success.  Any major problems will cause resize_ffs to exit with
     the non-zero exit(3) codes, so as to alert any invoking program or script that human inter-
     vention is required.

EXAMPLES
	   resize_ffs /dev/vg00/rlv1

     will enlarge the file system on the Logical Volume /dev/vg00/lv1 from Volume Group vg00 to
     the current device size.

SEE ALSO
     fs(5), fsck(8), newfs(8)

HISTORY
     The resize_ffs command first appeared in NetBSD 2.0.

AUTHORS
     der Mouse <mouse@rodents.montreal.qc.ca> (primary author)
     Jeff Rizzo <riz@NetBSD.org> (Byteswapped file system and UFS2 support)

     A big bug-finding kudos goes to John Kohl for finding the rotational layout bug referred to
     in the WARNING section above.

BUGS
     Can fail to shrink a file system when there actually is enough space, because it does not
     distinguish between a block allocated as a block and a block fully occupied by two or more
     frags.  This is unlikely to occur in practice; except for pathological cases, it can happen
     only when the new size is extremely close to the minimum possible.

     Has no intelligence whatever when it comes to allocating blocks to copy data into when
     shrinking.

     Doesn't currently support shrinking FFSv2 file systems.

BSD					 January 4, 2011				      BSD
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