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febootstrap-supermin-helper

NAME

febootstrap-supermin-helper - Reconstruct initramfs from supermin appliance.

SYNOPSIS

  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
 
 

DESCRIPTION

febootstrap-supermin-helper reconstructs a bootable kernel and initramfs from a supermin appliance. First you should be familiar with febootstrap(8), febootstrap-to-initramfs(8) and febootstrap-to-supermin(8).

PARAMETERS

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".

OPTIONS

-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 names for the "kernel" and "initrd", where the "initrd" is the appliance.

ext2

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).

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.

-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.

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.

As well as using febootstrap-minimize(8) it is worth checking for anything that is not necessary for your particular application and removing it by hand.

SEE ALSO

febootstrap(8), febootstrap-to-initramfs(8), febootstrap-to-supermin(8).

AUTHORS

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

COPYRIGHT

(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.