fakechroot-tcp(1)

NAME

fakechroot - gives a fake chroot environment

SYNOPSIS

fakechroot [-l|--lib library] [--faked faked-binary] [-i load-file] [-s save-file] [-u|--unknown-is-real ] [--] [command]

DESCRIPTION

fakechroot runs a command in an environment were it appears to have root privileges for file manipulation. This is almost the same as fakeroot(1) command with additional possibility to use chroot(8) command in such environment. This is useful for allowing users to create own chrooted environment with possibility to install another packages without need for root privileges.

fakechroot is heavily based on fakeroot(1) and replaces more library functions ( chroot(2), open(2), etc.) by ones that simulate the effect the real library functions would have had, had the user really been in chroot. These wrapper functions are in a shared library /usr/lib/libfakechroot.so* which is loaded through the LD_PRELOAD mechanism of the dynamic loader. (See ld.so(8))

In fake chroot you can install Debian bootstrap with `debootstrap --fakechroot' command. In this environment you can use i.e. apt-get(8) command to install another packages from common user's account.

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 fakechroot. Use ‘--’ if in the command you have other options that may confuse fakechroot's option parsing.

-s save-file: Save the fakechroot environment to save-file on exit. This file can be used to restore the environment later using -i. However, this file will leak and fakechroot will behave in odd ways unless you leave the files touched inside the fakechroot 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 fakechroot 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 fakechroot invocation is safe.

-u, --unknown-is-real: Use the real ownership of files previously unknown to fakechroot 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 fakechroot. Notice that inside the fake root environment file manipulation that requires root privileges succeeds, but is not really happening.

$ cp -a /usr/lib/debootstrap /tmp
$ cp -a /usr/sbin/debootstrap /tmp/debootstrap/scripts
$ ( cd /tmp/debootstrap; patch -f -p1 ) < debootstrap.diff
$ ( cd /tmp/debootstrap/scripts; patch -f -p1 ) < debootstrap.diff
$ fakechroot -s fakeroot.save
# cd /
# export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11
# DEBOOTSTRAP_DIR=/tmp/debootstrap /tmp/debootstrap/scripts/debootstrap sid /tmp/sid
# exit
$ rm -rf /tmp/sid/proc; ln -s /proc /tmp/sid
$ mv /tmp/sid/dev /tmp/sid/.dev; ln -s /dev /tmp/sid
$ fakechroot -i fakeroot.save
# cd /
# export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11
# chroot /tmp/sid /bin/bash
# sh /usr/share/doc/fakechroot/examples/savemode.sh
# apt-setup
# adduser --uid 1001 dexter
# nano /etc/apt/sources.lists
# apt-get update
# apt-get install build-essential devscripts
# cd /tmp
# apt-get source hello
# cd hello-*
# debuild --preserve-env -B
# exit

SECURITY ASPECTS

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

FILES

/usr/lib/libfakechroot/libfakechroot.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).

FAKECHROOT: The value is true for fake chroot environment.

FAKECHROOTDIR: The root directory for fake chroot environment.

LIMITATIONS

•: Every command executed within fakechroot needs to be linked to the same version of the C library as fakechroot itself. Because the Potato version of Debian now uses libc6 only (glibc2.1), this isn't that much of a problem any more.

•: Statically linked binaries doesn't work, especially ldconfig(8), so you have to wrap this command and i.e. set the dpkg diversion.

•: ldd(1) also doesn't work. You have to use wrapper.

•: You can override fake chroot with symlinks to the outside. It can be useful for accessing /proc or /dev directory.

•: ltrace(1) sometimes doesn't work. strace(1) does work pretty well.

•: lckpwdf() and ulckpwdf() are ignored so update-passwd(8) should work

•: Your real uid have to exist in /etc/passwd. Create it with `adduser --uid realuid realuser'.

•: debuild(1) cleans environment. Use --preserve-env option to prevent this behaviour.

•: fakeroot's -s option doesn't work well. You can use simple shell scripts to save and restore faked modes.

COPYING

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

AUTHOR

joost witteveen <[email protected]>

MANUAL PAGE

mostly by J.H.M. Dassen <[email protected]> Rather a lot mods/additions by joost.

Adapted to fakechroot by Piotr Roszatycki <[email protected]>