3.3.1.4 Configure and build in RAM ¶

Gnuastro’s configure and build process (the GNU build system) involves the creation, reading, and modification of a large number of files (input/output, or I/O). Therefore file I/O issues can directly affect the work of developers who need to configure and build Gnuastro numerous times. Some of these issues are listed below:

• I/O will cause wear and tear on both the HDDs (mechanical failures) and SSDs (decreasing the lifetime).
• Having the built files mixed with the source files can greatly affect backing up (synchronization) of source files (since it involves the management of a large number of small files that are regularly changed. Backup software can of course be configured to ignore the built files and directories. However, since the built files are mixed with the source files and can have a large variety, this will require a high level of customization.

One solution to address both these problems is to use the tmpfs file system. Any file in tmpfs is actually stored in the RAM (and possibly SWAP), not on HDDs or SSDs. The RAM is built for extensive and fast I/O. Therefore the large number of file I/Os associated with configuring and building will not harm the HDDs or SSDs. Due to the volatile nature of RAM, files in the tmpfs file-system will be permanently lost after a power-off. Since all configured and built files are derivative files (not files that have been directly written by hand) there is no problem in this and this feature can be considered as an automatic cleanup.

The modern GNU C library (and thus the Linux kernel) defines the /dev/shm directory for this purpose in the RAM (POSIX shared memory). To build in it, you can use the GNU build system’s ability to build in a separate directory (not necessarily in the source directory) as shown below. Just set SRCDIR as the address of Gnuastro’s top source directory (for example, where there is the unpacked tarball).

$ SRCDIR=/home/username/gnuastro
$ mkdir /dev/shm/tmp-gnuastro-build
$ cd /dev/shm/tmp-gnuastro-build
$ $SRCDIR/configure --srcdir=$SRCDIR
$ make

Gnuastro comes with a script to simplify this process of configuring and building in a different directory (a “clean” build), for more see Separate build and source directories.