Linux Certif

Toute la documentation sur la certification Linux LPI

virt-make-fs

NAME

virt-make-fs - Make a filesystem from a tar archive or files

SYNOPSIS

  virt-make-fs [--options] input.tar output.img
 
  virt-make-fs [--options] input.tar.gz output.img
 
  virt-make-fs [--options] directory output.img
 
 

DESCRIPTION

Virt-make-fs is a command line tool for creating a filesystem from a tar archive or some files in a directory. It is similar to tools like mkisofs(1), genisoimage(1) and mksquashfs(1). Unlike those tools, it can create common filesystem types like ext2/3 or NTFS, which can be useful if you want to attach these filesystems to existing virtual machines (eg. to import large amounts of read-only data to a VM).

Basic usage is:

  virt-make-fs input output
 
 

where "input" is either a directory containing files that you want to add, or a tar archive (either uncompressed tar or gzip-compressed tar); and "output" is a disk image. The input type is detected automatically. The output disk image defaults to a raw ext2 image unless you specify extra flags (see ``OPTIONS'' below).

EXTRA SPACE

Unlike formats such as tar and squashfs, a filesystem does not ``just fit'' the files that it contains, but might have extra space. Depending on how you are going to use the output, you might think this extra space is wasted and want to minimize it, or you might want to leave space so that more files can be added later. Virt-make-fs defaults to minimizing the extra space, but you can use the "--size" flag to leave space in the filesystem if you want it.

An alternative way to leave extra space but not make the output image any bigger is to use an alternative disk image format (instead of the default ``raw'' format). Using "--format=qcow2" will use the native QEmu/KVM qcow2 image format (check your hypervisor supports this before using it). This allows you to choose a large "--size" but the extra space won't actually be allocated in the image until you try to store something in it.

Don't forget that you can also use local commands including resize2fs(8) and virt-resize(1) to resize existing filesystems, or rerun virt-make-resize to build another image from scratch.

EXAMPLE

  virt-make-fs --format=qcow2 --size=+200M input output.img
 
 

FILESYSTEM TYPE

The default filesystem type is "ext2". Just about any filesystem type that libguestfs supports can be used (but not read-only formats like ISO9660). Here are some of the more common choices:

ext3

Note that ext3 filesystems contain a journal, typically 1-32 MB in size. If you are not going to use the filesystem in a way that requires the journal, then this is just wasted overhead.

ntfs or vfat

Useful if exporting data to a Windows guest.

Note for vfat: The tar archive or local directory must only contain files which are owned by root (ie. UID:GID = 0:0). The reason is that the tar program running within libguestfs is unable to change the ownership of non-root files, since vfat itself does not support this.

minix

Lower overhead than "ext2", but certain limitations on filename length and total filesystem size.

EXAMPLE

  virt-make-fs --type=minix input minixfs.img
 
 

TO PARTITION OR NOT TO PARTITION

Optionally virt-make-fs can add a partition table to the output disk.

Adding a partition can make the disk image more compatible with certain virtualized operating systems which don't expect to see a filesystem directly located on a block device (Linux doesn't care and will happily handle both types).

On the other hand, if you have a partition table then the output image is no longer a straight filesystem. For example you cannot run fsck(8) directly on a partitioned disk image. (However libguestfs tools such as guestfish(1) and virt-resize(1) can still be used).

EXAMPLE

Add an MBR partition:

  virt-make-fs --partition -- input disk.img
 
 

If the output disk image could be terabyte-sized or larger, it's better to use an EFI/GPT-compatible partition table:

  virt-make-fs --partition=gpt --size=+4T --format=qcow2 input disk.img
 
 

OPTIONS

--help

Display brief help.

--version

Display version number and exit.

--debug

Enable debugging information.

--size=<N>

--size=+<N>

-s <N>

-s +<N>

Use the "--size" (or "-s") option to choose the size of the output image.

If this option is not given, then the output image will be just large enough to contain all the files, with not much wasted space.

To choose a fixed size output disk, specify an absolute number followed by b/K/M/G/T/P/E to mean bytes, Kilobytes, Megabytes, Gigabytes, Terabytes, Petabytes or Exabytes. This must be large enough to contain all the input files, else you will get an error.

To leave extra space, specify "+" (plus sign) and a number followed by b/K/M/G/T/P/E to mean bytes, Kilobytes, Megabytes, Gigabytes, Terabytes, Petabytes or Exabytes. For example: "--size=+200M" means enough space for the input files, and (approximately) an extra 200 MB free space.

Note that virt-make-fs estimates free space, and therefore will not produce filesystems containing precisely the free space requested. (It is much more expensive and time-consuming to produce a filesystem which has precisely the desired free space).

--format=<fmt>

-F <fmt>

Choose the output disk image format.

The default is "raw" (raw disk image).

For other choices, see the qemu-img(1) manpage. The only other choice that would really make sense here is "qcow2".

--type=<fs>

-t <fs>

Choose the output filesystem type.

The default is "ext2".

Any filesystem which is supported read-write by libguestfs can be used here.

--partition

--partition=<parttype>

If specified, this flag adds an MBR partition table to the output disk image.

You can change the partition table type, eg. "--partition=gpt" for large disks.

Note that if you just use a lonesome "--partition", the Perl option parser might consider the next parameter to be the partition type. For example:

  virt-make-fs --partition input.tar ...
 
 

would cause virt-make-fs to think you wanted to use a partition type of "input.tar" which is completely wrong. To avoid this, use "--" (a double dash) between options and the input file argument:

  virt-make-fs --partition -- input.tar ...
 
 

SEE ALSO

guestfish(1), virt-resize(1), virt-tar(1), mkisofs(1), genisoimage(1), mksquashfs(1), mke2fs(8), resize2fs(8), guestfs(3), Sys::Guestfs(3), <http://libguestfs.org/>.

BUGS

When reporting bugs, please enable debugging and capture the complete output:

  export LIBGUESTFS_DEBUG=1
  virt-make-fs --debug [...] > /tmp/virt-make-fs.log 2>&1
 
 

Attach /tmp/virt-make-fs.log to a new bug report at <https://bugzilla.redhat.com/>

AUTHOR

Richard W.M. Jones <http://people.redhat.com/~rjones/>

COPYRIGHT

Copyright (C) 2010 Red Hat Inc.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.