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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 them‐
       selves 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  out‐
	      side the environment. Still, this can be useful. For example, it
	      can be used with rsync(1) to back up and restore whole directory
	      trees  complete  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 descrip‐
	      tor 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 suc‐
       ceeds, 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
       privileges.  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  pro‐
	      gram  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/own‐
	      erships.	(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
	      intercepted 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 unex‐
	      plainable 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 fake‐
	      root as small as possible, to limit the  likelihood  of  ‘colli‐
	      sions’.

       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  con‐
	      fused  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 "configure" from within fakeroot. As configure should
	      be  called  in  the   "debian/rules   build"   target,   running
	      "dpkg-buildpackage -rfakeroot" 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	 func‐
       tions 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/addi‐
       tions 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)
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