Imazu Hideyo
Matsushita Electric
On the other hand, saving entire / and /usr file systems for crash recovery is redundant because most files are unchanged, and copies exist on distribution media. In addition, restoring from backups after a disk crash is not as easy as an OS installation from distribution media because OS installation software does not necessarily include utilities to aid in doing so.
Difficulties in performing OS upgrades and disk crash recoveries are dramatically reduced if a complete set of ``changes'' (a set of changes is called a ``configuration'' in this paper) which have occurred throughout / and /usr can be observed and saved. ``Change'' means: 1) addition and deletion of files and directories; 2) modification of the content and status of files and directories. Dealing with changes is non- trivial because conventional commands such as tar, cpio, and dump cannot handle deletion and cannot alter the permissions of a file without restoring its contents.
If configurations can be stored under a single directory, OS upgrades become easier because the configuration can be restored by a simple operation after the upgrade. Instead of saving all files in / and /usr, one only needs to save changes to those file systems. One can easily perceive what the entire configuration is and modify merely a part of it.
In this paper, the author introduces a tool called ``OMNICONF'', which stores and restores ``configurations'' to and from a specified directory. OMNICONF is implemented in 2400 lines of Perl[1] code, under the concept shown above.
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