virt-make-fs - Make a filesystem from a tar archive or files
virt-make-fs [--options] input.tar output.img
virt-make-fs [--options] input.tar.gz output.img
virt-make-fs [--options] directory output.img
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).
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.
virt-make-fs --format=qcow2 --size=+200M input output.img
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:
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.
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.
Lower overhead than ext2, but certain limitations on filename
length and total filesystem size.
virt-make-fs --type=minix input minixfs.img
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).
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
Display brief help.
Display version number and exit.
Enable debugging information.
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).
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.
Choose the output filesystem type.
The default is ext2.
Any filesystem which is supported read-write by libguestfs can be used here.
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 ...
guestfish(1), virt-resize(1), virt-tar(1), mkisofs(1), genisoimage(1), mksquashfs(1), mke2fs(8), resize2fs(8), guestfs(3), the Sys::Guestfs(3) manpage, http://libguestfs.org/.
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/
Richard W.M. Jones http://people.redhat.com/~rjones/
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.