Re: Duplicate/False Mount Points

In article <C6A09055.42F16%nicknaym@[remove_this].gmail.com>,
Nick Naym <nicknaym@[remove_this].gmail.com> wrote:

In article jollyroger-31E71D.07550606082009@xxxxxxxxxxxxxxxxxxx, Jolly Roger
at jollyroger@xxxxxxxxx wrote on 8/6/09 8:55 AM:

In article <C69FD6B8.42E9E%nicknaym@[remove_this].gmail.com>,
Nick Naym <nicknaym@[remove_this].gmail.com> wrote:

BTW, I still don't understand this whole mount point business as it
relates
to the aliases appearing in /Volumes. AFAICT, the aliases in /Volumes
behave
as all aliases do: Double click on them, and they open their corresponding
(mounted) drives. Yet I was warned "don't delete the Barracuda alias in
the
/Volumes folder, or you'll lose your TM backups," the implication being
that
somehow that alias carries info about the drive's contents. If that indeed
is true (and it may not be -- I may have totally misunderstood it), where
does that data reside and how does the alias link to it?

When you mount a volume, it has to appear *somewhere* in the file
system. In Mac OS X, the default location for mounted external volumes
happens to be /Volumes. The OS creates a special file in that folder

"Special" file? In _which_ folder? In /Volumes? If so, where is it?

to
which it "attaches" the mounted volume. This alias is the mount point of

The alias is the "special" file?

Yep.

the volume - the gateway through which you have file system access to
the volume. Naturally, then, if you were to delete the contents of this
alias,

The aliases in /Volumes seem no different in character and behavior than
aliases in any other directory. Yet it seems that they are. I'm trying to
understand what makes them different, how those differences get "attached"
to them, and (if they are actual bits of code) where are those
"attachments?"

If I were you, I wouldn't be too concerned about the magic wand the OS
waves to make it happen. It's inconsequential, since it's transparent to
you. Suffice it to say that the contents of the mounted volume appear in
the above mentioned directory. For more detailed information, do a
Google search for "unix mount points".

you would, in effect, be deleting the contents of the volume
itself.

If I delete an "ordinary" alias, I do no harm. Here, all hell breaks loose.
So, here we are dealing with "special" aliases. But how does the system know
they're special (because they reside in /Volumes?), and where is the
detailed information/data that tells the system specifically what
distinguishes the aliases in /Volumes from each other?

We've been using the term alias, and this has bothered me for a couple
reasons for some time:

1. Technically, what gets created when you mount a volume is a
directory, not an alias. There is normally only one exception to this
rule, and that is the startup volume, which shows up as an alias to the
root of the startup file system (/). This is because the startup volume
contains the entire file system, so it is a special case that always
gets mounted at / in Mac OS X. As such, the OS adds an alias to it in
the Volumes folder as a convenience to you.

2. The term "alias" is badly chosen. Mac OS aliases are significantly
different from Unix links, and I am relatively certain a link is
actually what you are seeing for the startup volume in /Volumes. The
Finder displays aliases and linkx the same way, which can cause this
confusion.

At any rate, I doubt you would be allowed to delete the folder of a
mounted volume since it's in active use by the system as a mount point.
And you'll note that what I actually said was "if you were to delete the
contents of this alias you would, in effect, be deleting the contents of
the volume itself" - the key word being "contents".

--
Send responses to the relevant news group rather than email to me.
E-mail sent to this address may be devoured by my very hungry SPAM
filter. Due to Google's refusal to prevent spammers from posting
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Groups. Use a real news client if you want me to see your posts.

JR
.

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