Creating filesystems with compression

squashfs is a heavy-compression based read-only filesystem that is capable of compressing 2 to 3 GB of data onto a 700 MB file. If you have ever used a Linux LiveCD (or LiveUSB), they are built using squashfs . These CDs make use of a read-only compressed filesystem which keeps the root filesystem on a compressed file. It can be loopback mounted and loads a complete Linux environment. Thus, when some files are required by processes, they are decompressed and loaded onto the RAM and used.

squashfs can be useful when it is required to keep files heavily compressed and to access a few of them without extracting all the files. This is because completely extracting a large compressed archive takes a long time. However, if an archive is loopback mounted, it will be very fast since only the required portion of the compressed archive is decompressed when requested. Let's see how we can use squashfs.

Getting ready

squashfs internally uses compression algorithms...