Re: [gentoo-user] Don't be like stupid me!

[William Kenworthy <bill@kenworthy.id.au>]

On 10/2/24 23:56, Alan Mackenzie wrote:
> Hello, gentoo.
>
> I was wanting to do a pretty full build of my Emacs working repository.
> This involved first purging al *.elc files.  The way to do this is
>
>      $ find . -name '*.elc' | xargs rm
>
> .  But for some reason, I typed
>
>      $ find . '*.elc' | xargs rm
>
> .  I even carefully checked it before pressing RET.  However, press it I
> did, instantly deleting all files in my working directory.  OUTCH!
>
> So, I fell back on my backup from last Sunday.  After about 1½ hours
> trial and error, I had my source files as of last Sunday back again,
> though git could have been more helpful than it actually is.
>
> Thankfully, I had Emacs open, with all the files modified since Sunday
> in buffers.  So, I laboriously worked through Emacs's buffer list,
> saving those ones I'd since changed.
>
> I lost all my timestamps on the files, and lost all my Emacs backup
> files (things ending in ~ which Emacs constantly makes).  But my
> software builds and runs.
>
> It could have been a lot worse.  Boys and girls, don't use
>
>      $ find .... | xargs rm
>
> unless you really know what you're doing.  And even then, it's probably
> better not to.  ;-(
>
> It occurred to me fairly quickly after that press of RET that I could
> have done well with a COW snapshot facility, something which has been
> discussed at length on another recent thread.  I even have LVM on my
> machine for its RAID capabilities.  But I've never bothered before.  I
> mean "I'm too careful", amn't I?  ;-(  At least I do a weekly backup,
> though.
>
> So, in the end I managed to recover fairly well, thankfully.
>
No, you don't need a snapshot system - you need a proper backup system 
that stores the proper metadata.  When I was experimenting with 
snapshots (btrfs and moosefs) at different times I lost everything a few 
times with filesystem corruption which meant I lost the snapshots too.

Snapshots are NOT safe backups - treat them as a convenient copy ...

BillK