tools: Specify format of disks (RHBZ#642934,CVE-2010-3851).

[libguestfs.git] / tools / virt-resize

diff --git a/tools/virt-resize b/tools/virt-resize
index 0f0679e..8a71f96 100755 (executable)
--- a/tools/virt-resize
+++ b/tools/virt-resize
@@ -78,6 +78,11 @@ remaining space to /dev/sda2:
 
  virt-resize --resize /dev/sda1=+200M --expand /dev/sda2 olddisk newdisk
 
+As above, but the output format will be uncompressed qcow2:
+
+ qemu-img create -f qcow2 newdisk.qcow2 15G
+ virt-resize --expand /dev/sda2 olddisk newdisk.qcow2
+
 =head1 DETAILED USAGE
 
 =head2 EXPANDING A VIRTUAL MACHINE DISK
@@ -230,6 +235,25 @@ contents of a partition.  Deleting a partition removes it completely,
 but note that it also renumbers any partitions after the one which is
 deleted, which can leave some guests unbootable.
 
+=head2 QCOW2 AND NON-SPARSE RAW FORMATS
+
+If the input disk is in qcow2 format, then you may prefer that the
+output is in qcow2 format as well.  Alternately, virt-resize can
+convert the format on the fly.  The output format is simply determined
+by the format of the empty output container that you provide.  Thus to
+create qcow2 output, use:
+
+ qemu-img create [-c] -f qcow2 outdisk [size]
+
+instead of the truncate command (use C<-c> for a compressed disk).
+
+Similarly, to get non-sparse raw output use:
+
+ fallocate -l size outdisk
+
+(on older systems that don't have the L<fallocate(1)> command use
+C<dd if=/dev/zero of=outdisk bs=1M count=..>)
+
 =head1 OPTIONS
 
 =over 4
@@ -1380,6 +1404,23 @@ Windows may initiate a lengthy "chkdsk" on first boot after a resize,
 if NTFS partitions have been expanded.  This is just a safety check
 and (unless it find errors) is nothing to worry about.
 
+=head2 GUEST BOOT STUCK AT "GRUB"
+
+If a Linux guest does not boot after resizing, and the boot is stuck
+after printing C<GRUB> on the console, try reinstalling grub.  This
+sometimes happens on older (RHEL 5-era) guests, for reasons we don't
+fully understand, although we think is to do with partition alignment.
+
+ guestfish -i -a newdisk
+ ><fs> cat /boot/grub/device.map
+ # check the contents of this file are sensible or
+ # edit the file if necessary
+ ><fs> grub-install / /dev/vda
+ ><fs> exit
+
+For more flexible guest reconfiguration, including if you need to
+specify other parameters to grub-install, use L<virt-rescue(1)>.
+
 =head1 ALTERNATIVE TOOLS
 
 There are several proprietary tools for resizing partitions.  We
@@ -1418,6 +1459,10 @@ L<ntfsresize(8)>,
 L<virsh(1)>,
 L<parted(8)>,
 L<truncate(1)>,
+L<fallocate(1)>,
+L<grub(8)>,
+L<grub-install(8)>,
+L<virt-rescue(1)>,
 L<Sys::Guestfs(3)>,
 L<http://libguestfs.org/>.