113 lines
3.5 KiB
Groff
113 lines
3.5 KiB
Groff
.\" $NetBSD: resize_ffs.8,v 1.3 2003/03/10 09:23:23 wiz Exp $
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.\"
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.\" As its sole author, I explicitly place this man page in the public
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.\" domain. Anyone may use it in any way for any purpose (though I would
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.\" appreciate credit where it is due).
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.\"
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.\" /~\ The ASCII der Mouse
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.\" \ / Ribbon Campaign
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.\" X Against HTML mouse@rodents.montreal.qc.ca
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.\" / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
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.\"
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.Dd February 20, 2003
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.Dt RESIZE_FFS 8
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.Sh NAME
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.Nm resize_ffs
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.Nd resize an on-disk file system
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.Sh SYNOPSIS
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.Nm
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.Ar file-system-raw-device
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.Ar newsize
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.Sh DESCRIPTION
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.Nm
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resizes a file system on disk.
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.Ar file-system-raw-device
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is the name of the raw disk device where the file system resides;
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.Ar newsize
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is the desired new file system size, in sectors.
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(Sectors are almost always 512 bytes, and
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.Nm
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can both grow and shrink file systems.
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When growing, the disk device
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must of course be large enough to contain the new file system;
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.Nm
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simply extends the file system data structures into the new space.
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When shrinking,
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.Nm
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assumes this.
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It will not work correctly for file systems with other sector sizes.)
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.Nm
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has to copy anything that currently resides in the space being shrunk
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away; there must be enough space free on the file system for this to
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succeed.
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If there isn't,
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.Nm
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will complain and exit; when this happens, it attempts to always leave
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the file system in a consistent state, but it is probably a good idea to
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check the file system with
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.Xr fsck 8 .
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.Sh WARNING
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.Nm
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should still be considered experimental. It still needs to be validated
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with a rigorous regression test suite.
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.Em Interrupting
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.Nm
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.Em "may leave your file system in an inconsistent state and require a"
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.Em "restore from backup."
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It attempts to write in the proper order to avoid problems, but as it is
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still considered experimental, you should take great care when using it.
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.Pp
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When
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.Nm
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is applied to a consistent file system, it should always produce a
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consistent file system; if the file system is not consistent to start
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with,
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.Nm
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may misbehave, anything from dumping core to completely curdling the
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data.
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It's probably wise to
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.Xr fsck 8
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the file system before and after, just to be safe.
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.\" Remove this when (if) fsck gets fixed.
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.Pp
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There is a bug somewhere in fsck; it does not check certain data
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structures enough.
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A past version of this program had a bug that produced corrupted
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rotation layout summary tables, which would panic the kernel.
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This bug is believed fixed, and there are currently no
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known bugs in the program.
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However, you should be aware that just
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because fsck is happy with the file system does not mean it is intact.
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.Sh EXAMPLES
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.Ic resize_ffs Cm /dev/rsd1e 29574
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.Sh SEE ALSO
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.Xr fs 5 ,
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.Xr fsck 8 ,
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.Xr newfs 8
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.Sh HISTORY
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The
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.Nm
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command first appeared in
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.Nx 2.0 .
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.Sh AUTHORS
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.An der Mouse
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.Aq mouse@rodents.montreal.qc.ca
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.Pp
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A big bug-finding kudos goes to John Kohl for finding the rotational
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layout bug referred to in the
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.Sx WARNING
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section above.
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.Sh BUGS
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Has not been tested and probably won't work on opposite-endian file
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systems.
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.Pp
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Can fail to shrink a file system when there actually is enough space,
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because it does not distinguish between a block allocated as a block
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and a block fully occupied by two or more frags.
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This is unlikely to
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occur in practice; except for pathological cases, it can happen only
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when the new size is extremely close to the minimum possible.
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.Pp
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Has no intelligence whatever when it comes to allocating blocks to copy
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data into when shrinking.
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