Silicon Graphics IRIS Workstation User Manual page 53

IRIS WORKSTATION GUIDE 49
Appendix B:
Free-list blocks are written to the file system whenever they have been
modified and released by the operating system.
B.3 Corruption of the File System
A file system can become corrupted in a variety of ways. The most common of
these ways are improper shutdown procedures and hardware failures.
Improper System Shutdown and Startup
File systems may become cormpted when proper shutdown procedures are not
observed, e.g., forgetting to sync the system prior to halting the CPU, not
using the /etc/reboot -q command, physically write-protecting a mounted file
system, or taking a mounted file system off-line.
File systems may become further corrupted if proper startup procedures are not
observed, e.g., not checking a file system for inconsistencies, and not repairing
inconsistencies. Allowing a corrupted file system to be used (and, thus, to be
modified further) can be disastrous.
Hardware Failure
Any piece of hardware can fail at any time. Failures can be as subtle as a bad
block on a disk pack, or as blatant as a non-functional disk-controller.
B.4 Detection and Correction of Corruption
A quiescent file system may be checked for structural integrity by performing
3
consistency checks on the redundant data intrinsic to a file system. The
redundant data is either read from the file system or computed from other
known values. A quiescent state is important during the checking of a file
system because of the multi-pass nature of the fsck program.
When an inconsistency is discovered fsck reports the inconsistency for the
operator to choose a corrective action.
This section tells how to discover inconsistencies and possible corrective actions
for the super-block, the inodes, the indirect blocks, the data blocks containing
directory entries, and the free-list blocks. These corrective actions can be
performed interactively by the fsck command under control of the operator.
3. i.e., unmounted and not being written on.
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