Make the default setting YES for now to get some experience with it.
Note: If people starts seeing disk errors because of this then it
should not be backed.
With a small disk being 20GB these days, chances are pretty good that
an ailing sector will not be read while still being recoverable by
the drive.
Diskcheck daemon will read disks in the background at a low rate and
that way give the diskdrive a chance to detect and correct soft read
errors before they become hard errors.
Idea by: phk
Written by: ben
about non-existent mount directories (which would come
into existence after the real mount has occured) when just
testing for if there are any NFS filesystems in /etc/fstab.
PR: bin/26597
Submitted by: Dmitry Morozovsky <marck@rinet.ru>
MFC after: 3 days
systems were repo-copied from sys/miscfs to sys/fs.
- Renamed the following file systems and their modules:
fdesc -> fdescfs, portal -> portalfs, union -> unionfs.
- Renamed corresponding kernel options:
FDESC -> FDESCFS, PORTAL -> PORTALFS, UNION -> UNIONFS.
- Install header files for the above file systems.
- Removed bogus -I${.CURDIR}/../../sys CFLAGS from userland
Makefiles.
is not set. This allows admins to create a per-machine configuration file
while leaving the freebsd.mc template pristine. Provide a rule to create
`hostname`.mc from freebsd.mc if it doesn't exist.
PR: misc/26299
MFC after: 8 days
fsck checking. Applying these changes (typically via mergemaster)
will cause your system to start running background checks on all
your soft update enabled filesystems (provided that you have
a kernel with the required functionality, e.g., one built since
the end of April). Please report any and all problems to
mckusick@mckusick.com (not mckusick@freebsd.org which I read
infrequently). See the comment above the fsck command in /etc/rc
for instructions on how to disable background checking should it
cause you too much trouble.
Several FAQs:
1) Can I reboot before the background checks are done?
Ans) Yes, when the system restarts the checks will pick up
where they left off.
2) Can a crash during checking corrupt my filesystem?
Ans) No, recovered resources are returned to the system using soft
updates which ensure that the freeing is done in a safe order.
3) How will I know if any background checks are being done?
Ans) Filesystems that are to be checked in background will be listed
as `DEFER FOR BACKGROUND CHECKING' at the usual fsck check time
during system startup.
4) What happens to the output of the background checks?
Ans) It is sent to syslog `daemon' facility log level `notice'.
5) When will this feature be available in the 4.X kernel?
Ans) Never. It is much too radical and extensive a change to be
MFC'ed. Besides, it needs many months of experience and
tuning before it is ready for widespread use.
6) What happens if a background fsck fails (i.e., fsck finds
errors that would normally require a manual fsck)?
Ans) The filesystem will be marked as needing a manual fsck.
At the next system reboot, the check will be done in
foreground and the usual actions taken (usually a failure
to go multi-user until fsck has been run by hand on the
affected filesystem).
