NAME

       humfsify — convert a directory to the format needed by the UML humfs file system

SYNOPSIS

       humfsify [user]  [group]  [size]

DESCRIPTION

       This manual page documents briefly the humfsify command.

       This  manual  page  was written for the Debian GNU/Linux distribution because the original
       program does not have a manual page.  Instead, it has documentation in  HTML  format;  see
       below.

       humfsify is a Perl script necessary to convert a directory to a format expected by the UML
       humfs file system.

HISTORY

       UMLFS was born with the idea to substitute the Hostfs implementation with a proper one for
       the  UML  purpose:  when you manage files with Hostfs within UML you need to work with two
       different permission layers (the Host one and the UML one), which have different ideas  of
       ownerships.

       This  becomes  evident when you need to create a file as a non-root user on UML: you first
       need to interact with the UML file system implementation, and then with the host side.

       The result of a file creation on a mounted hostfs file system is not  what  you  expected:
       you  can  see  that  the  file permissions refer to the Host side user rather than the UML
       creator.

       The Host side user is to be intended as the UML instance launcher, meanwhile the UML  side
       user is the one you used to log in the UML instance.

       You  can  encounter  a  more-critical  problem when creating a device node, operation that
       usually requires root privileges: you used a common user to launch the UML and, since  the
       operation is done on the Host, it fails, even if you logged in as root.

       Thus  you need a set of tools which requires to bypass the Hostfs permission checks on the
       Host side: this is done by separating the file permissions  and  the  ownership  from  the
       host's files. This is the concept behind the HumFs and its humfsify implementation.

ARGUMENTS

       user      This  is  the user that needs to 'convert' a directory to the UML file system to
                 use UML.  This is the host user who will be using this  filesystem  from  within
                 UML.  It may be specified as either a user name or a numeric user id.

       group     This  is  the  group which your UML user belongs to.  This may be either a group
                 name or a numeric group id

       size      This is the size of the file system as seen within the UML instance. It must  be
                 expressed in Gigabytes ("G"), Megabytes ("M"), or KiloBytes ("K").

EXAMPLES

       Create a directory on the host and mount it with humfsify

       host% mkdir your-humfs-dir

       host% cd humfs-dir

       Within  this directory create a new one where you would like to have a UML-like hierarchy,
       i.e. you can loop-mount an UML rootfs

       host% mkdir dir-to-be-humsified

       host# mount -o loop rootfs /mnt

       host% cp -a /mnt dir-to-be-humsified/data

       host# humfsify user group 512M

       Then verify it on UML and mount the humfsified directory:

       UML# mount none /your-uml-host -t humfs -o

       where '/your-uml-mount-point' is the mount point on UML for the  humfsified  file  system,
       and  .../dir-to-be-humfsified  is  the humfsified directory in the example above. The '-t'
       mount option specifies that the file system is to be mounted as 'humfs'.

SEE ALSO

       The HostFs (link  to  URL  http://user-mode-linux.sourceforge.net/new/hostfs.html)   usage
       explanation within the User-Mode-Linux Web Site

AUTHOR

       humfsify was written by Jeff Dike.

       This  manual  page  was  written  by Stefano Melchior stefano.melchior@openlabs.it for the
       Debian GNU/Linux system, based on material in the Official User Mode Linux Web Site.

                                                                                      HUMFSIFY(1)