6.2. Alias sources

The previous section described how to identify a possible data source within ABLE. Typically these data sources are a raw unprocessed set of data, to be useful a data source is generally partitioned and has a filing system placed upon it. The process of building upon a raw data source is sometimes referred to as “cooking” which gives a cooked data source.

To make the users interaction with ABLE easier a set of alias sources are automatically generated. Each of these aliases may be referred to as a source in its own right. The ls command can be used to list these aliases.

Example 6.2. Using the ls command to list cooked sources

The ls command performed on the root directory.

>ls -l /
lrwxrwxrwx 1 0 0       11 hd0 -> (hdc1):ext2
lrwxrwxrwx 1 0 0        8 nvram0 -> 24cxx0p1
lrwxrwxrwx 1 0 0       15 flash1 -> (nand0p2):jffs2
lrwxrwxrwx 1 0 0        7 flash0 -> nand0p1

ABLE detects and creates a cooked source for every raw source that can provide files. Each of the raw sources will be examined for recognised filesystems and, if a partitioned device, each partition will be scanned. ABLE can interpret several filesystems, these include EXT2, FFS, ISO9660 (including rockridge extensions) and FAT. Filesystems are only scanned for on suitable sources i.e. ISO9660 filesystems would only be searched for on cdrom sources.

The user need not use the aliases and may specify the full source descriptor if desired. The sources “(hd0)” and “((hdc1):ext2)” from the previous examples are completely equivalent. The full construct may be used to attempt to force ABLE to interpret filesystems where it has not automatically detected one but this will almost certainly result in unexpected and incorrect behaviour.