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

[Alan Mackenzie <acm@muc.de>]

Hello, Bill.

On Sun, Feb 11, 2024 at 10:14:49 +0800, William Kenworthy wrote:

> On 10/2/24 23:56, Alan Mackenzie wrote:
> > 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.

I remembered after sending my original post that I stored the timestamps
of all the files in a file called timestamps.txt.  So a quick sed script
invocation on this file, and I had my timestamps back again!

> 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 ...

I was thinking of a snapshot more as an addition to backups, not an
alternative.  Such would have made it easier for me to recover yesterday.

A backup on the same medium as the filesystem isn't a backup at all.
I've never had a disk drive or SSD fail on me yet, but I'm not pushing my
luck.

> BillK

-- 
Alan Mackenzie (Nuremberg, Germany).