Saturday, July 12, 2008

Re: [BLUG] scp -p preserving ownership through root user

On Thu, 3 Jul 2008, Steven Black wrote:

> You put root's home directory in /home? Just FYI, that's not a
> safe thing to do. It means if you're trying to recover a system
> and /home isn't available you have no configuration files for
> root, and additionally, any files created by root in the home
> directory will land in /. There's nothing like being in a tough
> spot and trying to recover a system and having none of your
> carefully configured system behave as expected. This is what
> will happen if you have root's home directory in /home.
>
> The way the file-system should be structured is that you can
> perform all recovery operations with *only* the / partition
> mounted.
>
> Back in the day the root user didn't have a home directory. It
> was called "root", in part, because the home directory was in
> the root of the file-system. People decided this was a bad idea
> years and years ago, though.
>
> I highly recommend you spend some time playing around with some
> of the command-line options. It is a bad habit to
> over-complicate your command-lines. You can inadvertently find
> yourself having problems that other people just don't
> understand, as they're side-effects of command-line option
> interaction.
>
> Additionally, when you use a lot of command-line options,
> you're opening yourself up to more bugs and hard to reproduce
> behavior. While a lot of the programs you use are probably
> reliable and well-tested, in many environments the rare/obscure
> combinations command-line arguments are the exact places where
> the rare/obscure bugs lie. Option A may work well and be
> well-tested. Option B may work well and be well-tested. Option
> A+Option B may interact in ways that are non-obvious, flat-out
> buggy, and potentially unreproducible.
>
>> But the relevant point to what I was answering is only
>> that tar does not follow symlinks by default; if you want it
>> to track them down and include them, you have to tell it to.
>> Otherwise, using it for the purpose I did, you gradually
>> accumulate obscure but irritating failures of exactly the kind
>> of things I was trying to preserve.
>
> I had to scratch my head on this one.
>
> Why would you want tar to follow symlinks when copying home
> directories?
>
> Tar normally stores and restores symlinks as symlinks. If
> you're symlinking to things which change locations across
> machines in your network, then it is expected that things fall
> apart.
>
> For instance, at home with my personal user account, I keep all
> my data stored one level deep with a dash of source control,
> and a makefile here or there to establish symlinks. It allows
> me to easily backup the data I want to keep and ignore the crap
> that doesn't interest me. All of the symlinks I use in my home
> directory relate directly to other directories in my home
> directory. (And they should all be relative links, so they can
> be moved safely. This also allows me to have multiple copies of
> that data tree and retain internal consistency.)
>
> This also means that if symlinks were followed, I would get
> massive data duplication, some of the source control would be
> violated, and I'd no longer be able to as easily create backups
> of the stuff that is important to me. As an example of some of
> the massive data duplication: Some things have created both a
> 'Music' and a 'music' folder in my home directory in the past,
> both of these, for me, are symlinks to Media/Music, but Media
> itself is a symlink in to the directory I backup regularly. If
> you follow those symlinks, then all my music would be
> duplicated 3 more times.

Wow! What a haul! I'm going to have to go on chewing on
all that for quite a while yet to absorb it as t deserves; but I
thank you immensely for such a trove of clues. Like many
autodidacts, I'm probably stuffed to the ears with things I think
I know that just ain't so -- alas!

--
Beartooth Implacable, Neo-Redneck Linux Enthusiast
Freedom is my issue : I'm pro-choice, pro-right-to-die,
pro-gun, and pro-term-limits. Without defiance, no liberty.
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