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6.2.4 Staged Installs

The GNU Build System’s make install and make uninstall interface does not exactly fit the needs of a system administrator who has to deploy and upgrade packages on lots of hosts. In other words, the GNU Build System does not replace a package manager.

Such package managers usually need to know which files have been installed by a package, so a mere make install is inappropriate.

The DESTDIR variable can be used to perform a staged installation. The package should be configured as if it was going to be installed in its final location (e.g., --prefix /usr), but when running make install, the DESTDIR should be set to the absolute name of a directory into which the installation will be diverted. From this directory it is easy to review which files are being installed where, and finally copy them to their final location by some means.

For instance here is how we could create a binary package containing a snapshot of all the files to be installed.

~/amhello-1.0 % ./configure --prefix /usr
~/amhello-1.0 % make
~/amhello-1.0 % make DESTDIR=$HOME/inst install
~/amhello-1.0 % cd ~/inst
~/inst % find . -type f -print > ../files.lst
~/inst % tar zcvf ~/amhello-1.0-i686.tar.gz `cat ../files.lst`

After this example, amhello-1.0-i686.tar.gz is ready to be uncompressed in / on many hosts. (Using `cat ../files.lst` instead of ‘.’ as argument for tar avoids entries for each subdirectory in the archive: we would not like tar to restore the modification time of /, /usr/, etc.)

Note that when building packages for several architectures, it might be convenient to use make install-data and make install-exec (see The Two Parts of Install) to gather architecture-independent files in a single package.

See Install for more information.

Automake generates support for the DESTDIR variable in all install rules. DESTDIR is used during the ‘make install’ step to relocate install objects into a staging area. Each object and path is prefixed with the value of DESTDIR before being copied into the install area. Here is an example of typical DESTDIR usage:

mkdir /tmp/staging &&
make DESTDIR=/tmp/staging install

The mkdir command avoids a security problem if the attacker creates a symbolic link from /tmp/staging to a victim area; then make places install objects in a directory tree built under /tmp/staging. If /gnu/bin/foo and /gnu/share/aclocal/foo.m4 are to be installed, the above command would install /tmp/staging/gnu/bin/foo and /tmp/staging/gnu/share/aclocal/foo.m4.

This feature is commonly used to build install images and packages.

Support for DESTDIR is implemented by coding it directly into the install rules. If your uses a local install rule (e.g., install-exec-local) or an install hook, then you must write that code to respect DESTDIR.

See Makefile Conventions in The GNU Coding Standards for another usage example.

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