FEBOOTSTRAP-SUPERMIN-HELPER(Virtualization SuppoFEBOOTSTRAP-SUPERMIN-HELPER(8)NAMEfebootstrap-supermin-helper - Reconstruct initramfs from supermin
SYNOPSISfebootstrap-supermin-helper supermin.img hostfiles.txt host_cpu kernel initrd
febootstrap-supermin-helper input [...] host_cpu kernel initrd
febootstrap-supermin-helper-f ext2 input [...] host_cpu kernel initrd appliance
febootstrap-supermin-helper-f checksum input [...] host_cpu
DESCRIPTIONfebootstrap-supermin-helper reconstructs a bootable kernel and
initramfs from a supermin appliance. First you should be familiar with
Of the required parameters, the first few are input files, and the last
two or three are output files.
"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).
"host_cpu" should be the host CPU, eg. "x86_64" or "i686".
"kernel", "initrd" and "appliance" are the temporary output files that
this script produces. These output files are meant to be used just for
booting the appliance, and should be deleted straight afterwards. The
extra "appliance" parameter is only required when the format is "ext2".
None of these parameters are needed for the checksum output "-f
Select the output format for the appliance. Possible formats are:
A Linux initramfs. This is the default.
In this case you have to supply names for the "kernel" and
"initrd", where the "initrd" is the appliance.
An ext2 filesystem.
In this case you have to supply names for the "kernel", a small
"initrd" which is used just to locate the appliance, and the
"appliance" (the ext2 filesystem).
Output a checksum.
This prints a checksum which only changes when one of the input
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.
Copy the kernel 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.
If this option is specified, then "file" should be a list of
wildcards matching kernel module names, eg:
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
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.
Run febootstrap-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 febootstrap-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 febootstrap-supermin-helper uses bash in parts, this will result
in the creation of an appliance with a mixture of ownerships.
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
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
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.
The corresponding module path is guessed from the kernel name, but
you can override that by setting "FEBOOTSTRAP_MODULES".
If "FEBOOTSTRAP_KERNEL" and "FEBOOTSTRAP_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.
This has no effect if "FEBOOTSTRAP_KERNEL" is not set.
Richard W.M. Jones <rjones @ redhat . com>
(C) Copyright 2009-2011 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.
febootstrap-3.20 2012-12-03 FEBOOTSTRAP-SUPERMIN-HELPER(8)