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bug#30946: 26.0.90; TRAMP cannot access some files when using hops
From: |
Phil Sainty |
Subject: |
bug#30946: 26.0.90; TRAMP cannot access some files when using hops |
Date: |
Mon, 31 Dec 2018 11:01:46 +1300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 |
(resending this to just the bug address, after unarchiving)
On 26/03/18 9:42 PM, Nicolas Petton wrote:
> As discussed on the emacs-devel mailing list, when using tramp with
> multiple hops like the following:
>
> C-x C-f /ssh:me@example.com|sudo:localhost:/etc/deluser.conf
>
> Tramp opens an empty buffer, without showing any error message.
>
> I understand now that the second hop should be "sudo:example.com:",
> but it felt intuitive to use localhost, and for most files on the
> remote host it actually worked.
I'd suspect that https://stackoverflow.com/a/16408592/324105 explains
why it 'worked':
> The trap here is that sudo:: does actually appear to work -- however
> when you do that the HOST for the dynamic proxy entry will be the
> hostname you originated from rather than the host you connected
> to. This will not only look confusing (as the wrong host will be
> displayed in the file paths), but it will also mean that any
> subsequent attempt to use sudo:: on your localhost will instead be
> proxied to the remote server!
i.e. /ssh:me@example.com|sudo:localhost was previously creating a proxy
that said that when you request files as root@localhost (for *any*
tramp method!) it should proxy via "/ssh:me@example.com:". The sudo
method didn't actually need or care about the specified host, so that
"worked" -- but the proxy you'd created was then a problem waiting to
bite you.
Ooohh.
Michael, that actually still remains a problem in the new version.
Despite the error message, the unintended proxy is still created,
and hence can still break things.
i.e. I try to visit:
/ssh:me@example.com|sudo:localhost
I get the new error message:
Host name ‘localhost’ does not match ‘^example.com$’
but I *also* get a new proxy entry:
("localhost" "root" "/ssh:me@example.com:")
So when I then visit:
/sudo:localhost:
I get the error message:
Host name ‘localhost’ does not match ‘^example.com$’
etc, etc...
Conversely, it seems that the "::" case has been attended to so that
it now transparently DWIM ?
i.e. When I try /ssh:me@example.com|sudo:: I get a proxy entry of:
("example.com" "root" "/ssh:me@example.com:")
whereas in earlier versions of Emacs I get the undesirable:
("<FOO>" "root" "/ssh:me@example.com:")
Where <FOO> is my local hostname.
That's excellent, and possibly also deserves a note in the NEWS?
Currently it reads:
*** For some connection methods, like "su" or "sudo", the host name in
ad-hoc multi-hop file names must match the previous hop.
We could perhaps append:
If the hostname is left empty (e.g. "sudo::") then the host from the
previous hop is used automatically.
cheers,
-Phil
p.s. I find the new error slightly confusing to dismiss. It's not
entirely obvious how to get back to the prompt. Not a big problem,
as ideally people don't run into it at all, but I just thought I'd
mention it.
The error sticks around persistently until I type C-g, at which point
I get a new error "Tramp: Opening connection for root@localhost using
sudo...failed". That error also sticks around for a couple of seconds,
which is long enough to make one suspect that it also needs to be
dismissed with C-g -- which will actually exit the minibuffer entirely,
meaning you can't simply edit the incorrect path to fix the problem,
but must start over.
(So the correct sequence is C-g and then either wait a couple of
seconds, or just start typing blindly.)
It would be nice if that was a bit smoother -- but again, I don't
think this is a significant issue in reality, so I wouldn't worry
about it unless you think it's easy to deal with.
- bug#30946: 26.0.90; TRAMP cannot access some files when using hops,
Phil Sainty <=