Aux Base: Library

As I mentioned before, a good basic understanding of ext2 and its successors has been a key element in the popularity of the filesystem. In addition to the usual tools for making and checking ext FS are some good debugging tools, such as debugfs and dumpe2fs, which allow power users to dig really deep into the filesystem to analyze it, fix bugs, or save data.

For these tools to work, they must have appropriate insider knowledge of the relevant member of the ext FS family. If a detail of the filesystem changes, the developers are forced to adapt the associated tools. As the number of helper programs grows, the maintenance effort can become immense. The trick used by ext2 and its successors is to collect filesystem information in the libext2fs library, against which the tools are linked (Listing 2). Ironically, the Btrfs tool, btrfs-convert, also uses this library, allowing you to convert an existing ext FS in situ to the Btrfs competitor [14].

# ldd /usr/sbin/debugfs /usr/sbin/tune2fs > \
  /usr/sbin/mkfs.ext* /usr/sbin/fsck.ext* > \
  /usr/sbin/btrfs-convert | grep ext2fs | > \
  awk '{print $1}' | uniq libext2fs.so.2

Conclusions

With more than 20 years of history, the ext family of filesystems is one of the most sustainable open source projects in the Linux environment. Its success hinges on several factors. To begin, the 1993 design on one hand allowed for future extension, and on the other hand offered strong backward compatibility. Additionally, the makeup of the development team has remained stable. Early adoption into the Linux kernel didn't hurt, either, helping the filesystem family attract a large developer and user community. Early nomination of ext FS as the standard filesystem for Linux is both a cause and consequence of the success of ext2 and its relatives.

However, it still remains to be seen how ext FS will fare in the coming years (see the box "Looking to the Future"). What will happen after the changing of the guard by Btrfs or XFS? Will the Linux Android smartphone continue to fly the banner of the ext family?