62 lines
2.8 KiB
Plaintext
62 lines
2.8 KiB
Plaintext
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@node Enabling Relocatability
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@section Enabling Relocatability
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It has been a pain for many users of GNU packages for a long time that
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packages are not relocatable. It means a user cannot copy a program,
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installed by another user on the same machine, to his home directory,
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and have it work correctly (including i18n). So many users need to go
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through @code{configure; make; make install} with all its
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dependencies, options, and hurdles.
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Most package management systems, that allow the user to install
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pre-built binaries of the packages, solve the ``ease of
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installation'' problem, but they hardwire path names, usually to
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@file{/usr} or @file{/usr/local}. This means that users need root
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privileges to install a binary package, and prevents installing two
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different versions of the same binary package.
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A relocatable program can be moved or copied to a different location
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on the file system. It is possible to make symlinks to the installed
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and moved programs, and invoke them through the symlink. It is
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possible to do the same thing with a hard link @emph{only} if the hard
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link file is in the same directory as the real program.
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To configure a program to be relocatable, add
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@option{--enable-relocatable} to the @command{configure} command line.
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On some OSes the executables remember the location of shared libraries
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and prefer them over any other search path. Therefore, such an
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executable will look for its shared libraries first in the original
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installation directory and only then in the current installation
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directory. Thus, for reliability, it is best to also give a
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@option{--prefix} option pointing to a directory that does not exist
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now and which never will be created, e.g.@:
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@option{--prefix=/nonexistent}. You may use
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@code{DESTDIR=@var{dest-dir}} on the @command{make} command line to
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avoid installing into that directory.
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We do not recommend using a prefix writable by unprivileged users
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(e.g.@: @file{/tmp/inst$$}) because such a directory can be recreated
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by an unprivileged user after the original directory has been removed.
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We also do not recommend prefixes that might be behind an automounter
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(e.g.@: @file{$HOME/inst$$}) because of the performance impact of
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directory searching.
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Here's a sample installation run that takes into account all these
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recommendations:
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@example
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./configure --enable-relocatable --prefix=/nonexistent
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make
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make install DESTDIR=/tmp/inst$$
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@end example
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Installation with @option{--enable-relocatable} will not work for
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setuid or setgid executables, because such executables search only
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system library paths for security reasons.
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The runtime penalty and size penalty are negligible on GNU/Linux (just
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one system call more when an executable is launched), and small on
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other systems (the wrapper program just sets an environment variable
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and executes the real program).
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