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Linux 2.6 - man page for fakeroot-tcp (linux section 1)

fakeroot(1)				  Debian manual 			      fakeroot(1)

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

       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]

       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  ar-
       chives 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/libfake-
       root.so* which is loaded through the LD_PRELOAD mechanism  of  the  dynamic  loader.  (See

       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 pro-
       grams 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 fake-
       root. Especially configure and friends don't like it when the system suddenly behaves dif-
       ferently  from what they expect. (or, they randomly unset some environment variables, some
       of which fakeroot needs).

       -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 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 pretend-
	      ing 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.

       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
       $ fakeroot /bin/bash
       #  whoami
       # 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).

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

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

	      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/own-
	      erships.	(assuming the daemon and connecting program  were  started  by	the  same


	      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

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

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

	      touch foo
	      ls -al foo

	      or the other way around,

	      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  prob-
	      lems,  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  num-
	      ber  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 "configure" from within fakeroot. As configure should be called in the
	      "debian/rules build" target, running "dpkg-buildpackage -rfakeroot" correctly takes
	      care of this.

       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).

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

       joost witteveen

       Clint Adams

       Timo Savola

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

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

Debian Project				  6 August 2004 			      fakeroot(1)

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