=head1 NAME

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

=head1 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

=head1 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
L<mkisofs(1)>, L<genisoimage(1)> and L<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).

To create blank disks, use L<virt-format(1)>.  To create complex
layouts, use L<guestfish(1)>.

Basic usage is:

 virt-make-fs input output.img

where C<input> is either a directory containing files that you want to
add, or a tar archive (either uncompressed tar or gzip-compressed
tar); and F<output.img> is a disk image.  The input type is detected
automatically.  The output disk image defaults to a raw ext2 sparse
image unless you specify extra flags (see L</OPTIONS> below).

=head2 FILESYSTEM TYPE

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

=over 4

=item I<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.

=item I<ntfs> or I<vfat>

Useful if exporting data to a Windows guest.

=item I<minix>

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

=back

=head3 EXAMPLE

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

=head2 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
L<fsck(8)> directly on a partitioned disk image.  (However libguestfs
tools such as L<guestfish(1)> and L<virt-resize(1)> can still be
used).

=head3 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

=head2 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 I<--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 I<--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 I<--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
L<resize2fs(8)> and L<virt-resize(1)> to resize existing filesystems,
or rerun virt-make-fs to build another image from scratch.

=head3 EXAMPLE

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

=head1 OPTIONS

=over 4

=item B<--help>

Display brief help.

=item B<--blocksize=512>

=item B<--blocksize=4096>

This parameter sets the sector size of the output disk image.

The default is C<512> bytes.

See also L<guestfs(3)/guestfs_add_drive_opts>.

=item B<--floppy>

Create a virtual floppy disk.

Currently this preselects the size (1440K), partition type (MBR) and
filesystem type (VFAT).  In future it may also choose the geometry.

=item B<--size=>N

=item B<--size=+>N

=item B<-s> N

=item B<-s> B<+>N

Use the I<--size> (or I<-s>) option to choose the size of the output
image.

If this option is I<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 C<+> (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: I<--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).

=item B<--format=>FMT

=item B<-F> FMT

Choose the output disk image format.

The default is C<raw> (raw sparse disk image).

=item B<--type=>FS

=item B<-t> FS

Choose the output filesystem type.

The default is C<ext2>.

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

=item B<--label=>LABEL

Set the filesystem label.

=item B<--partition>

=item B<--partition=>PARTTYPE

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

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

For MBR, virt-make-fs sets the partition type byte automatically.

=item B<-v>

=item B<--verbose>

Enable debugging information.

=item B<-V>

=item B<--version>

Display version number and exit.

=item B<-x>

Enable libguestfs trace.

=back

=head1 SEE ALSO

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

=head1 AUTHOR

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

=head1 COPYRIGHT

Copyright (C) 2010-2025 Red Hat Inc.
