4. Appendix A − Fsck Error Conditions 4.1. Conventions Fsck is a multi-pass ﬁle system check program. Each ﬁle system pass invokes a different Phase of the fsck program. After the initial setup, fsck performs successive Phases over each ﬁle system, checking blocks and sizes, path-names, connectivity, reference counts, and the map of free blocks, (possibly rebuilding it, and performs some cleanup. Normally fsck is run non-interactively to preen the ﬁle systems after an unclean halt. While preening ale system, it will only ﬁx corruptions that are expected to occur from an unclean halt. These actions area proper subset of the actions that fsck will take when it is running interactively. Throughout this appendix many errors have several options that the operator can take. When an inconsistency is detected, fsck reports the error condition to the operator. If a response is required, fsck prints a prompt message and waits fora response. When preening most errors are fatal. For those that are expected, the response taken is noted. This appendix explains the meaning of each error condition, the possible responses, and the related error conditions. The error conditions are organized by the Phase of the fsck program in which they can occur. The error conditions that may occur in more than one Phase will be discussed in initialization.