NAMN¶

fakeroot - utför ett kommando i en miljö som fejkar root-privilegier för filmanipulation

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]

BESKRIVNING¶

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 arbetar genom att ersätta biblioteksfunktionerna för filrättighetsmodifiering (chmod(2), stat(2), osv) med sådana som simulerar effekten som de riktiga biblioteksfunktionerna skulle ha haft om användaren verkligen varit root. Dessa funktioner finns samlade i biblioteket /usr/lib/libfakeroot.so* som laddas genom LD_PRELOAD-mekanismen hos den dynamiska länkaren (se ld.so(8))

Om du planerar att bygga paket med hjälp av fakeroot, försök först att bygga fakeroot-paketet: "debian/rules build"-stadiet har ett par tester (som mestadels testar efter buggar i gamla versioner av fakeroot). Om dessa tester misslyckas (till exempel på grund av att du har vissa libc5-program på ditt system) så är det troligt att du också kommer att misslyckas bygga andra paket, och det är möjligt att dessa fel blir betydligt svårare att hitta.

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).

FLAGGOR¶

-l library, --lib library

Ange ett alternativt bibliotek med ersättningsfunktioner.

--faked binär

Ange en alternativ binär att använda istället för faked(1).

[--] kommando

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 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.

EXEMPEL¶

Här är ett exempel på hur fakeroot kan användas. Notera att i den fejkade root-miljön så lyckas filmanipulering som kräver root-privilegier, trots att den egentligen inte utförs.

$  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

Enbart de operationer som användaren joost skulle kunna ha genomfört som sig själv utförs på riktigt.

fakeroot skrevs speciellt i syfte att ge användare möjlighet att skapa Debian GNU/Linux-paket (i deb(5) format) utan att behöva root-privilegier. Detta kan utföras genom kommandon såsom dpkg-buildpackage -rfakeroot eller debuild -rfakeroot (-rfakeroot är numera standard i debuild, så du behöver inte ens använda den parametern).

SÄKERHETSASPEKTER¶

fakeroot är ett vanligt program utan setuid. Det ger inte användaren några extra privilegier, och minskar inte systemets säkerhet.

FILER¶

/usr/lib/libfakeroot/libfakeroot.so* Det delade bibliotek som innehåller ersättningsfunktionerna.

MILJÖ¶

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 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/

BEGRÄNSNINGAR¶

Biblioteksversioner

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
    

eller omvänt,

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 (och liknande program)

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.

BUGGAR¶

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).

LICENS¶

fakeroot distribueras under GNU General Public License. (GPL 2.0 eller senare).

FÖRFATTARE¶

joost witteveen

<joostje@debian.org>

Clint Adams

<schizo@debian.org>

Timo Savola

ÖVERSÄTTNING¶

David Weinehall <tao@kernel.org>

MANUALSIDA¶

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

SE ÄVEN¶

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