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NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

       fakeroot [-l|--lib library] [--faked faked-binary] [--] [command]

DESCRIPTION    [Toc]    [Back]

       fakeroot runs a command in an environment were 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 have 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  environemnt variables, some of which
       fakeroot needs).

OPTIONS    [Toc]    [Back]

       --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.

       EXAMPLES    [Toc]    [Back]
	      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

	      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

SECURITY ASPECTS    [Toc]    [Back]

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

FILES    [Toc]    [Back]

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

ENVIRONMENT    [Toc]    [Back]

	      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 filesystem's permissions/ownerships.
  (assuming the daemon and connecting program were started
	      by the same user).

LIMITATIONS    [Toc]    [Back]

       Library versions
	      Every command executed within fakeroot needs to be linked to the
	      same version of the C library as fakeroot  itself.  Because  the
	      potato  version  of  debian now uses libc6 only (glibc2.1), this
	      isn't that much of a problem any more.

	      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
	      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) 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
	      likelyhood of `collisions'.

       GNU configure (and other such programs)    [Toc]    [Back]
	      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	"dpkgbuildpackage
 -rfakeroot" correctly takes care of this.

BUGS    [Toc]    [Back]

       It doens'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,  the
       open  will  suceed,  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    [Toc]    [Back]

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

AUTHOR    [Toc]    [Back]

       joost witteveen <joostje@debian.org>

MANUAL PAGE    [Toc]    [Back]

       mostly  by  J.H.M.  Dassen  <jdassen@wi.LeidenUniv.nl>  Rather  a   lot
       mods/additions by joost.

SEE ALSO    [Toc]    [Back]

       faked(1) dpkg-buildpackage(1), build(1L) /usr/doc/fakeroot/DEBUG

Debian Project			 26 July 1997			   fakeroot(1)
[ Back ]
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