Hints & Tips for Optimizing Linux Disk Usage

It seems that no matter how much hard disk storage you have, it quickly becomes full. Because Linux is free, many users are on a limited budget and can't afford to simply buy more hardware. This article describes some simple techniques for making the best use of the disk storage you have now.
Compressing Files

If you cannot delete files, there are several options available for making them smaller.

Compression programs can make files significantly smaller. The GNU gzip program provides excellent compression. It is ideal for compressing data files such as documents and source code that do not need to be on-line at all times. The best option to zip will provide the highest level of compression.

Emacs can also be configured to automatically uncompress files when editing; see the lisp file uncompress.el included with UGN emacs version 19. Another space savings with emacs is to compress info pages; GNU emacs version 19 automatically handles reading compressed info pages.

If you maintain multiple revisions of files, particularly source code, then a revision control system such as RCS can save space. Only the differences between file revisions are stored.

Compressing man pages was mentioned previous.ly Traditionally this is done using the standard compress program Some man programs can handle gzip compressed man page as well (you may need to continue using the .Z file extension).

Existing binary files sometimes contain debug information. They can be made smaller using the strip command. This was the case, for example, for the GNU emacs binary I uploaded from an archive site.

For new compiles, you can minimize the size of the binaries (once they are debugged) by compiling without debug and with full optimization (e.g. -O2 for gcc). The linker flags -s and -N can also be useful; see the gcc and ld man pages for more details.

Advanced Techniques

More advanced users can try some of the more sophisticated techniques described in this section.

The Linux second extended filesystem reserves a portion of the disk for use only by root. This is useful for preventing users from filling the disk, but may not be desirable in some cases (e.g. a disk containing user files only). By default 5% of the disk is reserved. You can change this when formatting a partition; see the mke2fs man page for more details.

Transparently Compressed Executables (TCX), is a utility for compressing binary files in a way that still allows them to be executed. The author is Stewart Forster. It saves disk space at the expense of a minor delay in startup time. It is most useful for large programs that are infrequently executed. I found this package to be quite effective and reliable; it can be found on your local Linux archive site.

For compressing data files, the zlibc package can be used. It works by patching the Linux system calls such as open that read data files, and uncompresses the files on the fly. I have not used this package, but the author claims that compression ratios of 1:3 can easily be achieved. The package can be found on Linux archive sites in both source and binary form; the author is Alain Knaff.

There have been discussions about implementing a compressed filesystem for Linux, similar in concept to what exists for MS-DOS. The ext2 filesystem already has some hooks to allow this to be added. This may be the ultimate solution for optimizing disk usage.

For More Information:

More information on the ideas discussed in this article can be found in the following sources. All are available on the major Linux archive sites.

Linux Kernel Hacker's Guide, Michael K. Johnson

Linux System Administrator's Guide, Lars Wirzenius.

Linux man pages

See also the documentation included with the packages mentioned in this article ( zlibc, tcx, etc...).

By day, Jeff Tranter is a software designer for a large telecommunications manufacturer in Kanata, Ontario (Canada's Silicon Valley North). For him, Linux is the realization of a dream to have an affordable Unix compatible system at home that rivals commercial workstations and is just plan fun to hack around with.

Jeff Tranter by day is a software designer for a large telecommunications manufacturer in Kanata, Ontario (Canada's Silicon Valley North). For him, Linux is the realization of a dream to have an affordable Unix compatible system at home that rivals commercial workstations and is just plan fun to hack around with.


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