switch users --> black screen, no response [in 12.04]

[Liam Proven]

On 19 May 2013 18:04, rikona <rikona at sonic.net> wrote:
>
> I was not looking for miracles. :-) Let's say I was working on a very
> large data file, and had added to it over a 3-5 day period. When the
> disk is 'fixed' is this file completely gone, or like it was before I
> started working on it, or has part but not all of the new info, or
> since it has been 4-5 hours since data was added, even might have the
> latest data? What is that file most likely to look like?

I don't know. I don't know the disk filesystem, the contents of the
disk, the contents of the file, the write pattern of the file or
anything.

What it should do is replay the journal to the last disk write that
successfully completed, leaving you with an intact, valid file as of
the *filesystem's view* of that file. The last disk write that
completed will be redone, any incomplete disk writes will be rolled
back and you will have a complete copy of the file as of the last disk
write.

This is entirely separate from the *program's view* of the file. It
might have written a complex data structure in half a dozen (or
34782341089137) disk write operations. Some of these operations will
be completed; some may not if the system crash was part-way through a
sequence of writes.

If in doubt, reconnect drive, copy pre-fsck file to another volume,
then fsck it, then copy post-fsck file and compare the two.

Better still, image the whole drive.

For what it is worth, I got bitten by this problem badly due to a
serious system crash in the late 1990s, and after that, I kept all
important work on a server on the other end of a network cable. This
way, the filesystem on the disks is under the control of an entirely
separate computer, not my workstation. No severity of crash can
corrupt the filesystem of a different machine. It can of course
corrupt any files that were open at the time of the crash, but all the
rest will be fine.

These days, I still do this, but I tend to keep work-in-progress on
Dropbox, and every time I am about to make a major change, I do a File
Save As... under a new name, so I end up with:

GotR.doc
GotR v1.1.doc
GotR v1.2.doc
GotR mk2.doc
GotR mk2.1.doc
GotR mk3.doc
GotR mk4.doc
GorR mk5.doc
GotR mk5.1 - GC.doc
GotR mk6.doc
GotR mk6.1.doc

(Reconstructed from memory, that's a real sequence.)

This means that I can always go back to my previous version.

(Aside: I learned programming on a VAX with proper filesystem
versioning - every file change generates a new file version, e.g.

WUMPUS.FOR;62

I miss this on inferior modern OSs like Unix and Windows, and so try
to recreate it by hand.)



--
Liam Proven • Profile: http://lproven.livejournal.com/profile
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