HUMFSIFY(1) General Commands Manual HUMFSIFY(1)
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 own-
erships.
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 imple-
mentation, 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)