NAME

       supermin-helper - Reconstruct initramfs from supermin appliance.

SYNOPSIS

       New style (since supermin 4.1.5):

        supermin-helper [-f cpio|ext2] -o outputdir input [input...]

       or:

        supermin-helper [-f cpio|ext2] --output-kernel kernel \
          [--output-dtb dtb] --output-initrd initrd \
          [--output-appliance appliance] input [input...]

       or:

        supermin-helper -f checksum input [input ...]

       Old style (still supported in this version but deprecated):

        supermin-helper [-f cpio] supermin.img hostfiles.txt host_cpu kernel initrd
        supermin-helper [-f cpio] input [...] host_cpu kernel initrd

        supermin-helper -f ext2 input [...] host_cpu kernel initrd appliance

        supermin-helper -f checksum input [...] host_cpu

DESCRIPTION

       supermin-helper reconstructs a bootable kernel and initramfs from a supermin appliance.
       First you should be familiar with supermin(1).

PARAMETERS

       Specify the input file(s), and -o or --output-* flags indicating where you want the
       appliance to be written.

       Use the -f option to select what type of appliance you want.

       "supermin.img" and "hostfiles.txt" are the input files which describe the supermin
       appliance.  (You can also use a directory name here which is searched for files).

       To write the appliance to a directory, use -o outputdir.  The directory should already
       exist.  Files called "outputdir/kernel", "outputdir/dtb", "outputdir/initrd" and/or
       "outputdir/appliance" will be written.  (Not all files are written, it depends on what
       kind of appliance you asked for and what architecture you are running on)

       To write files with specific names instead, use the --output-kernel, --output-dtb,
       --output-initrd and/or --output-appliance options.

OPTIONS

       --help
           Display brief command line usage, and exit.

       --copy-kernel
           Copy the kernel (and device tree, if created) instead of symlinking to the kernel in
           "/boot".

           This is fractionally slower, but is necessary if you want to change the permissions or
           SELinux label on the kernel or device tree.

       --dtb wildcard
           If specified, search for a device tree which is compatible with the selected kernel
           and the name of which matches the given wildcard.  You can use a wildcard such as
           "vexpress-*a9*.dtb" which would match "vexpress-v2p-ca9.dtb".

           Notes:

           •   You may need to quote the wildcard to prevent it from being expanded by your
               shell.

           •   If no --dtb option is given, no device tree will be looked for.

           •   You only need a device tree on architectures such as ARM and PowerPC which use
               them.  On other architectures, don't use this option.

           •   If you use this option and no compatible device tree can be found, supermin-helper
               will exit with an error.

       -f fmt
       --format fmt
           Select the output format for the appliance.  Possible formats are:

           cpio
               A Linux initramfs.  This is the default.

               In this case you have to supply output names for the "kernel" and "initrd".  The
               "initrd" is the appliance.

               Note that cpio(1) might not be able to extract this file fully.  The format used
               by the Linux kernel is not quite a true cpio file.

           ext2
               An ext2 filesystem.

               In this case you have to supply output names for the "kernel", a small "initrd"
               which is used just to locate the appliance, and the "appliance" (the ext2
               filesystem).

           checksum
               Output a checksum.

               This prints a checksum which only changes when one of the input files changes.

               You can use this in order to cache the output of a previous run of this program:
               computing the checksum is much quicker than building an appliance, and you only
               need to invalidate the cache (and consequently rebuild the appliance) when the
               checksum changes.  Note that the host_cpu and the UID of the current user are
               included in the checksum.

       --host-cpu cpu
           Specify the host CPU (eg. "i686", "x86_64").  This is used as a substring match when
           searching for compatible kernels.  If not specified, it defaults to the host CPU that
           supermin-helper was compiled on.

       -k file
       --kmods file
           If this option is specified, then "file" should be a list of wildcards matching kernel
           module names, eg:

            virtio*.ko
            scsi*.ko
            piix.ko

           In this case, only kernel modules matching those wildcards will be included in the
           output appliance.  Note: You must resolve any dependencies yourself as this does not
           pull in dependent modules automatically.

           If this option is not specified, then every kernel module from the host will be
           included.  This is safer, but can produce rather large appliances which need a lot
           more memory to boot.

       -o outputdir
           Write the appliance to the named directory.  Two or more of the following files will
           be created (the exact files created depends on the type of appliance you asked for and
           the architecture):

           "outputdir/kernel"
               (ie. A file literally called "kernel" in the directory outputdir that you
               specified).  This is usually a symlink to the kernel, unless you gave the
               --copy-kernel option.

           "outputdir/dtb"
               The device tree.  See also the --dtb option.

               This is only created on architectures that use device trees, eg. ARM.

               This is usually a symlink to the device tree binary file, unless you gave the
               --copy-kernel option.

           "outputdir/initrd"
               The initrd.  For -f cpio this also contains the full appliance.  For -f ext2 this
               is just a small initrd which is sufficient to find and mount the appliance disk.

           "outputdir/appliance"
               The appliance disk (only for -f ext2).

       --output-kernel kernel
           Instead of using the literal hard-coded name "kernel", write the kernel to the named
           path.  This overrides the -o outputdir option (if present).

       --output-dtb dtb
           Instead of using the literal hard-coded name "dtb", write the device tree to the named
           path.  This overrides the -o outputdir option (if present).

       --output-initrd initrd
           Instead of using the literal hard-coded name "initrd", write the initrd to the named
           path.  This overrides the -o outputdir option (if present).

       --output-initrd appliance
           Instead of using the literal hard-coded name "appliance", write the initrd to the
           named path.  This overrides the -o outputdir option (if present).

       -u user
       --user user
       -g group
       --group group
           Run supermin-helper as an alternate user and/or group.  "user" and "group" can be
           specified as either a name, which will be resolved using the system name service, or a
           uid/gid.  Use of these options requires root privileges.

           Use of these options is required if running supermin-helper as root with the effective
           uid/gid set to non-root.  Bash will reset the effective uid/gid to the real uid/gid
           when invoked.  As supermin-helper uses bash in parts, this will result in the creation
           of an appliance with a mixture of ownerships.

       -v
       --verbose
           Enable verbose messages (give multiple times for more verbosity).

       -V
       --version
           Display version number and exit.

COMPRESSED INPUT FILES

       supermin-helper ≥ 4.1.4 supports gzip-compressed input cpio image files.  "hostfiles"
       cannot be compressed.

       Compressing input files saves space, but can make supermin-helper run fractionally slower.

SPEED

       In libguestfs, on a mid-range Intel-based PC, we reconstruct the initramfs using this
       script in around 1/5th of a second (assuming a "hot cache" - it's rather slower when run
       the first time on a cold cache).

       Some tips to improve performance:

       •   Use a kernel module whitelist (the "--kmods" option), and only list the kernel modules
           you really need.

       •   Minimize the appliance, removing as much extraneous junk as possible.

ENVIRONMENT VARIABLES

       SUPERMIN_KERNEL
           If this environment variable is set, then automatic selection of the kernel is
           bypassed and this kernel is used.

           The environment variable should point to a kernel file, eg. "/boot/vmlinuz-3.0.x86_64"

           The corresponding module path is guessed from the kernel name, but you can override
           that by setting "SUPERMIN_MODULES".

       SUPERMIN_MODULES
           If "SUPERMIN_KERNEL" and "SUPERMIN_MODULES" are both set, then automatic selection of
           the kernel is bypassed and the kernel and module path are set to these values.

           The environment variable should point to a module directory, eg.
           "/lib/modules/3.0.x86_64/"

           This has no effect if "SUPERMIN_KERNEL" is not set.

       SUPERMIN_DTB
           Force the given device tree file to be used.

SEE ALSO

       supermin(1).

AUTHORS

       Richard W.M. Jones <rjones @ redhat . com>

COPYRIGHT

       (C) Copyright 2009-2013 Red Hat Inc., <http://people.redhat.com/~rjones/supermin>.

       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.