Ubuntu Manpage: supermin - Tool for creating supermin appliances

NAME

       supermin - Tool for creating supermin appliances

SYNOPSIS

        supermin [-o OUTPUTDIR] --names LIST OF PKGS ...
        supermin [-o OUTPUTDIR] PKG FILE NAMES ...

DESCRIPTION

       Supermin is a tool for building supermin appliances.  These are tiny appliances (similar to virtual
       machines), usually around 100KB in size, which get fully instantiated on-the-fly in a fraction of a
       second when you need to boot one of them.

       Originally "fe" in "febootstrap" stood for "Fedora", but this tool is now distro-independent and can
       build supermin appliances for several popular Linux distros, and adding support for others is reasonably
       easy.  For this reason, starting with version 4, we have renamed the tool "supermin".

       Note that this manual page documents supermin 4.x which is a complete rewrite and quite different from
       febootstrap 2.x.  If you are looking for the febootstrap 2.x tools, then this is not the right place.

   BASIC OPERATION
       There are two modes for using supermin.  With the --names parameter, supermin takes a list of package
       names and creates a supermin appliance containing those packages and all dependencies that those packages
       require.  In this mode supermin usually needs network access because it may need to consult package
       repositories in order to work out dependencies and download packages.

       Without --names, supermin takes a list of packages (ie.  filenames of locally available packages).  This
       package set must be complete and consistent with no dependencies outside the set of packages you provide.
       In this mode supermin does not require any network access.  It works by looking at the package files
       themselves.

       By "package" we mean the RPM, DEB, (etc.) package.  A package name might be the fully qualified name (eg.
       "coreutils-8.5-7.fc14.x86_64") or some abbreviation (eg. "coreutils").  The precise format of the name
       and what abbreviations are allowed depends on the package manager.

       The supermin appliance that supermin writes consists of two files called "hostfiles" and "base.img" (see
       "SUPERMIN APPLIANCES" below).  By default these are written to the current directory.  If you specify the
       -o OUTPUTDIR option then these files are written to the named directory instead (traditionally this
       directory is named "supermin.d" but you can call it whatever you want).

       In all cases supermin can only build a supermin appliance which is identical in distro, version and
       architecture to the host.  It does not do cross-builds.

OPTIONS

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

       --exclude REGEXP
           After doing dependency resolution, exclude packages which match the regular expression.

           This option is only used with --names, and it can be given multiple times on the command line.

       --names
           Provide  a  list of package names, instead of providing packages directly.  In this mode supermin may
           require network access.  See "BASIC OPERATION" above.

       --no-warnings
           Don't print warnings about packaging problems.

       -o outputdir
           Select the output directory where the two supermin  appliance  files  are  written  ("hostfiles"  and
           "base.img").   The default directory is the current directory.  Note that if this files exist already
           in the output directory then they will be overwritten.

       --packager-config CONFIGFILE
           Set the configuration file for the package manager.  This allows you to  specify  alternate  software
           repositories.

           For   ArchLinux,   this  sets  the  pacman  configuration  file  (default  "/etc/pacman.conf").   See
           pacman.conf(5).

           For Yum/RPM distributions, this sets the  yum  configuration  file  (default  "/etc/yum.conf").   See
           yum.conf(5).

       --save-temps
           Don't remove temporary files and directories on exit.  This is useful for debugging.

       --use-installed
           If  packages  are  already  installed,  use  the  contents  (from  the  local  filesystem) instead of
           downloading them.

           Note that this can cause malformed appliances  if  local  files  have  been  changed  from  what  was
           originally in the package.  This is particularly a problem for configuration files.

           However this option is useful in some controlled situations: for example when using supermin inside a
           freshly installed chroot.

       -v
       --verbose
           Enable verbose messages.

       -V
       --version
           Print the package name and version number, and exit.

       --yum-config CONFIGFILE
           This is a deprecated alias for --packager-config CONFIGFILE.

SUPERMIN APPLIANCES

Supermin appliances consist of just enough information to be able to build an appliance containing the
same operating system (Linux version, distro, release etc) as the host OS. Since the host and appliance
share many common files such as "/bin/bash" and "/lib/libc.so" there is no reason to ship these files in
the appliance. They can simply be read from the host on demand when the appliance is launched.
Therefore to save space we just store the names of the host files that we want.

There are some files which cannot just be copied from the host in this way. These include configuration
files which the host admin might have edited. So along with the list of host files, we also store a
skeleton base image which contains these files and the outline directory structure.

Therefore the supermin appliance normally consists of at least two control files:

hostfiles
The list of files that are to be copied from the host. This is a plain text file with one pathname
per line. Directories are included in this file.

Paths can contain wildcards, which are expanded when the appliance is created, eg:

/etc/yum.repos.d/*.repo

would copy all of the "*.repo" files into the appliance.

Each pathname in the file should start with a "/" character. (In older versions of febootstrap,
paths started with "./" and were relative to the root directory, but you should not do that in new
files).

base.img
This uncompressed cpio file contains the skeleton filesystem. Mostly it contains directories and a
few configuration files.

All paths in the cpio file should be relative to the root directory of the appliance.

Note that unlike "hostfiles", paths and directories in the base image don't need to have any
relationship to the host filesystem.

base.img.gz
Since supermin ≥ 4.1.4, any cpio image files may be gzip-compressed to save disk space. "hostfiles"
cannot be compressed. The supermin program won't create these files. You need to compress the
output yourself, eg by doing:

gzip -9 supermin.d/*.img

RECONSTRUCTING THE APPLIANCE
The separate tool supermin-helper(1) is used to reconstruct an appliance from the hostfiles and base
image files.

This program in fact iterates recursively over the files and directories passed to it. A common layout
is:

supermin.d/
supermin.d/base.img
supermin.d/extra.img
supermin.d/hostfiles

and then invoking supermin-helper with just the "supermin.d" directory path as an argument.

In this way extra files can be added to the appliance just by creating another cpio file ("extra.img" in
the example above) and dropping it into the directory. When the appliance is constructed, the extra
files will appear in the appliance.

DIRECTORIES BEFORE FILES

In order for supermin-helper to run quickly, it does not know how to create directories automatically.
Inside hostfiles and the cpio files, directories must be specified before any files that they contain.
For example:

/usr
/usr/sbin
/usr/sbin/serviced

It is fine to list the same directory name multiple times.

LEXICOGRAPHICAL ORDER

supermin-helper visits the supermin control files in lexicographical order. Thus in the example above,
in the order "base.img" -> "extra.img" -> "hostfiles".

This has an important effect: files contained in later cpio files overwrite earlier files, and
directories do not need to be specified if they have already been created in earlier control files.

EXAMPLE OF CREATING EXTRA CPIO FILE

You can create a file like "extra.img" very easily using a shell snippet similar to this one:

cd $tmpdir
mkdir -p usr/sbin
cp /path/to/serviced usr/sbin/
echo -e "usr\nusr/sbin\nusr/sbin/serviced" |
cpio --quiet -o -H newc > extra.img
rm -rf usr

Notice how we instruct cpio to create intermediate directories.

MINIMIZING THE SUPERMIN APPLIANCE
You may want to "minimize" the supermin appliance in order to save time and space when it is
instantiated. Typically you might want to remove documentation, info files, man pages and locales. We
used to provide a separate tool called "febootstrap-minimize" for this purpose, but it is no longer
provided. Instead you can post-process "hostfiles" yourself to remove any files or directories that you
don't want (by removing lines from the file). Be careful what you remove because files may be necessary
for correct operation of the appliance.

For example:

< supermin.d/hostfiles \
grep -v '^/usr/share/man/' |
grep -v '^/usr/share/doc/' |
grep -v '^/usr/share/info/' > supermin.d/hostfiles-t
mv supermin.d/hostfiles-t supermin.d/hostfiles

KERNEL AND KERNEL MODULES
Usually the kernel and kernel modules are not included in the supermin appliance. When the appliance is
instantiated, the kernel modules from the host kernel are copied in, and it is booted using the host
kernel.

supermin-helper is able to choose the best host kernel available to boot the appliance. Users can
override this by setting environment variables (see supermin-helper(1)).

BOOTING AND CACHING THE SUPERMIN APPLIANCE
For fastest boot times you should cache the output of supermin-helper. See the libguestfs source file
"src/appliance.c" for an example of how this is done.

ENFORCING AVAILABILITY OF HOSTFILES
supermin-helper builds the appliance by copying in host files as listed in "hostfiles". For this to work
those host files must be available. We usually enforce this by adding requirements (eg. RPM "Requires:"
lines) on the package that uses the supermin appliance, so that package cannot be installed without
pulling in the dependent packages and thus making sure the host files are available.

AUTHORS

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

       •   Matthew Booth mbooth@redhat.com

COPYRIGHT

       Copyright (C) 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.

supermin-4.1.5                                     2013-11-12                                        SUPERMIN(1)