fakeroot(1)							   Debian manual						       fakeroot(1)

NAME

       fakeroot - run a command in an environment faking root privileges for file manipulation

SYNOPSIS

       fakeroot  [-l|--lib  library]  [--faked	faked-binary]  [-i  load-file] [-s save-file] [-u|--unknown-is-real ] [-b|--fd-base ] [-h|--help ]
       [-v|--version ] [--] [command]

DESCRIPTION

       fakeroot runs a command in an environment wherein it appears to have root privileges for file manipulation.  This is  useful  for  allowing
       users  to create archives (tar, ar, .deb etc.) with files in them with root permissions/ownership.  Without fakeroot one would need to have
       root privileges to create the constituent files of the archives with the correct permissions and ownership, and then pack them up,  or  one
       would have to construct the archives directly, without using the archiver.

       fakeroot  works	by  replacing  the  file manipulation library functions (chmod(2), stat(2) etc.) by ones that simulate the effect the real
       library functions would have had, had the user really been root. These wrapper functions are in a shared  library  /usr/lib/libfakeroot.so*
       which is loaded through the LD_PRELOAD mechanism of the dynamic loader. (See ld.so(8))

       If  you	intend	to  build packages with fakeroot, please try building the fakeroot package first: the "debian/rules build" stage has a few
       tests (testing mostly for bugs in old fakeroot versions). If those tests fail (for example because you have certain libc5 programs on  your
       system), other packages you build with fakeroot will quite likely fail too, but possibly in much more subtle ways.

       Also,  note that it's best not to do the building of the binaries themselves under fakeroot. Especially configure and friends don't like it
       when the system suddenly behaves differently from what they expect. (or, they randomly unset some  environment  variables,  some  of  which
       fakeroot needs).

OPTIONS

       -l library, --lib library
	      Specify an alternative wrapper library.

       --faked binary
	      Specify an alternative binary to use as faked.

       [--] command
	      Any  command  you  want  to be ran as fakeroot. Use '--' if in the command you have other options that may confuse fakeroot's option
	      parsing.

       -s save-file
	      Save the fakeroot environment to save-file on exit. This file can be used to restore the environment later using -i.  However,  this
	      file  will  leak	and fakeroot will behave in odd ways unless you leave the files touched inside the fakeroot alone when outside the
	      environment. Still, this can be useful. For example, it can be used with rsync(1) to back up and restore whole directory trees  com-
	      plete  with  user,  group  and  device  information  without  needing to be root. See /usr/share/doc/fakeroot/README.saving for more
	      details.

       -i load-file
	      Load a fakeroot environment previously saved using -s from load-file.  Note that this does not implicitly save the file, use  -s	as
	      well for that behaviour. Using the same file for both -i and -s in a single fakeroot invocation is safe.

       -u, --unknown-is-real
	      Use the real ownership of files previously unknown to fakeroot instead of pretending they are owned by root:root.

       -b fd  Specify fd base (TCP mode only). fd is the minimum file descriptor number to use for TCP connections; this may be important to avoid
	      conflicts with the file descriptors used by the programs being run under fakeroot.

       -h     Display help.

       -v     Display version.

EXAMPLES

       Here is an example session with fakeroot.  Notice that inside the fake root environment file manipulation  that	requires  root	privileges
       succeeds, but is not really happening.

       $  whoami
       joost
       $ fakeroot /bin/bash
       #  whoami
       root
       # mknod hda3 b 3 1
       # ls -ld hda3
       brw-r--r--   1 root     root	  3,   1 Jul  2 22:58 hda3
       # chown joost:root hda3
       # ls -ld hda3
       brw-r--r--   1 joost    root	  3,   1 Jul  2 22:58 hda3
       # ls -ld /
       drwxr-xr-x  20 root     root	    1024 Jun 17 21:50 /
       # chown joost:users /
       # chmod a+w /
       # ls -ld /
       drwxrwxrwx  20 joost    users	    1024 Jun 17 21:50 /
       # exit
       $ ls -ld /
       drwxr-xr-x  20 root     root	    1024 Jun 17 21:50 //
       $ ls -ld hda3
       -rw-r--r--   1 joost    users	       0 Jul  2 22:58 hda3

       Only the effects that user joost could do anyway happen for real.

       fakeroot was specifically written to enable users to create Debian GNU/Linux packages (in the deb(5) format) without giving them root priv-
       ileges.	This can be done by commands like dpkg-buildpackage -rfakeroot or debuild -rfakeroot (actually, -rfakeroot is default  in  debuild
       nowadays, so you don't need that argument).

SECURITY ASPECTS

       fakeroot is a regular, non-setuid program. It does not enhance a user's privileges, or decrease the system's security.

FILES

       /usr/lib/libfakeroot/libfakeroot.so* The shared library containing the wrapper functions.

ENVIRONMENT

       FAKEROOTKEY
	      The  key	used to communicate with the fakeroot daemon. Any program started with the right LD_PRELOAD and a FAKEROOTKEY of a running
	      daemon will automatically connect to that daemon, and have the  same  "fake"  view  of  the  file  system's  permissions/ownerships.
	      (assuming the daemon and connecting program were started by the same user).

       LD_LIBRARY_PATH

       LD_PRELOAD
	      Fakeroot	is  implemented  by  wrapping  system  calls.	This  is  accomplished	by  setting  LD_LIBRARY_PATH=/usr/lib/fakeroot and
	      LD_PRELOAD=libfakeroot.so.0.  That library is loaded before the system's C library, and so most of the library functions are  inter-
	      cepted by it.  If you need to set either LD_LIBRARY_PATH or LD_PRELOAD from within a fakeroot environment, it should be set relative
	      to the given paths, as in LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/foo/bar/

LIMITATIONS

       Library versions
	      Every command executed within fakeroot needs to be linked to the same version of the C library as fakeroot itself.

       open()/create()
	      fakeroot doesn't wrap open(), create(), etc. So, if user joost does either

	      touch foo
	      fakeroot
	      ls -al foo

	      or the other way around,

	      fakeroot
	      touch foo
	      ls -al foo

	      fakeroot has no way of knowing that in the first case, the owner of foo really should be joost while the second case it should  have
	      been  root.  For the Debian packaging, defaulting to giving all "unknown" files uid=gid=0, is always OK. The real way around this is
	      to wrap open() and create(), but that creates other problems, as demonstrated by the libtricks package. This  package  wrapped  many
	      more  functions,	and  tried to do a lot more than fakeroot .  It turned out that a minor upgrade of libc (from one where the stat()
	      function didn't use open() to one with a stat() function that did (in some cases) use open()), would cause  unexplainable  segfaults
	      (that  is,  the  libc6  stat() called the wrapped open(), which would then call the libc6 stat(), etc).  Fixing them wasn't all that
	      easy, but once fixed, it was just a matter of time before another function started to use open(), never mind trying to port it to  a
	      different  operating  system.  Thus I decided to keep the number of functions wrapped by fakeroot as small as possible, to limit the
	      likelihood of 'collisions'.

       GNU configure (and other such programs)
	      fakeroot, in effect, is changing the way the system behaves. Programs that probe the system like GNU configure may get  confused	by
	      this (or if they don't, they may stress fakeroot so much that fakeroot itself becomes confused). So, it's advisable not to run "con-
	      figure" from within fakeroot. As configure should be called in the "debian/rules build" target, running  "dpkg-buildpackage  -rfake-
	      root" correctly takes care of this.

BUGS

       It  doesn't wrap open(). This isn't bad by itself, but if a program does open("file", O_WRONLY, 000), writes to file "file", closes it, and
       then again tries to open to read the file, then that open fails, as the mode of the file will be 000. The bug is  that  if  root  does  the
       same,  open()  will succeed, as the file permissions aren't checked at all for root. I choose not to wrap open(), as open() is used by many
       other functions in libc (also those that are already wrapped), thus creating loops (or possible future loops, when  the	implementation	of
       various libc functions slightly change).

COPYING

       fakeroot is distributed under the GNU General Public License.  (GPL 2.0 or greater).

AUTHORS

       joost witteveen
	      <joostje@debian.org>

       Clint Adams
	      <clint@debian.org>

       Timo Savola

MANUAL PAGE

       mostly by J.H.M. Dassen <jdassen@debian.org> Rather a lot mods/additions by joost and Clint.

SEE ALSO

       faked(1) dpkg-buildpackage(1), debuild(1) /usr/share/doc/fakeroot/DEBUG

Debian Project							   6 August 2004						       fakeroot(1)