febootstrap-supermin-helper - Reconstruct initramfs from supermin appliance.
febootstrap-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
febootstrap-supermin-helper reconstructs a bootable kernel and initramfs from a supermin appliance. First you should be familiar with febootstrap(8).
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 checksum.
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 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.
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.
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 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.
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 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. /lib/modules/3.0.x86_64/
This has no effect if FEBOOTSTRAP_KERNEL is not set.
febootstrap(8).
Richard W.M. Jones <rjones @ redhat . com>
(C) Copyright 2009-2010 Red Hat Inc., http://people.redhat.com/~rjones/febootstrap.
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.