[gentoo-amd64] Strange ssh behaviour

[gentoo-amd64] Strange ssh behaviour

[Mark Haney]

This might be a bit off topic, but I'm at my wits' end.  I have a server
that uses PAM/LDAP for authentication.  A recent update broke PAM and
took me a couple of days to fix.  But now, when I ssh into the box, I
get no output from any commands.  su,ls,cat all just return to the
prompt without showing me any output.  I can env and echo fine and tab
completion works, so I know the shell is okay.  I just don't have any
clue on what to try next.

Any ideas would be appreciated. TIA.


-- 
Ceterum censeo, Carthago delenda est.

Mark Haney
Sr. Systems Administrator
ERC Broadband
(828) 350-2415


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[gentoo-amd64] Re: Strange ssh behaviour

[Duncan]

"Mark Haney" <mhaney@ercbroadband.org> posted
451BEFB2.6090303@ercbroadband.org, excerpted below, on  Thu, 28 Sep 2006
11:52:18 -0400:

> This might be a bit off topic, but I'm at my wits' end.  I have a server
> that uses PAM/LDAP for authentication.  A recent update broke PAM and
> took me a couple of days to fix.  But now, when I ssh into the box, I
> get no output from any commands.  su,ls,cat all just return to the
> prompt without showing me any output.  I can env and echo fine and tab
> completion works, so I know the shell is okay.  I just don't have any
> clue on what to try next.

I don't do remote admin so have no direct experience, but I've read of two
issues you might be running into.

1)  Apparently it is or has been default to build stage-3 and GRP packages
with USE=acl.  People who turn that flag off and do an emerge --depclean
without doing an emerge --newuse first end up breaking their system,
because all the ordinary utilities are built against access control list
libraries and a depclean removes them, leaving non-functional binaries. 
That's why there's the BIG BIG WARNING about using depclean without doing
an emerge --newuse (and preferrably a revdep-rebuild both before and
after, just to be sure) first.  Unfortunately, there are a LOT of people
who can't seem to read warnings, even BIG BIG warnings, that end up with
broken systems.

2)  There was a recent authentication issue where LDAP based remote
authentication and access was in use.  Apparently, it was a problem of
trying to authenticate a user in LDAP before the network was up to do so. 
This caused VERY SLOW boots, and altho I'm not aware of it causing your
issue directly, it's possible it could be related.  Part of the fix was to
ensure all necessary boot accounts could be authenticated locally, not
just over the network using LDAP -- IOW ensure there are entries in
the local passwd and group files as appropriate, and that the UID/GID
align with what is expected.

More than that, you'll probably need to get help from someone with more
direct experience.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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Re: [gentoo-amd64] Strange ssh behaviour

[Boyd Stephen Smith Jr.]

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On Thursday 28 September 2006 10:52, "Mark Haney" <mhaney@ercbroadband.org> 
wrote about '[gentoo-amd64] Strange ssh behaviour':
> [N]ow, when I ssh into the box, I
> get no output from any commands.  su,ls,cat all just return to the
> prompt without showing me any output.

Try running strace on a command on the remote side -- see if that indicates 
anything.

-- 
"If there's one thing we've established over the years,
it's that the vast majority of our users don't have the slightest
clue what's best for them in terms of package stability."
-- Gentoo Developer Ciaran McCreesh

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Re: [gentoo-amd64] Strange ssh behaviour

[Mark Haney]

Boyd Stephen Smith Jr. wrote:
> On Thursday 28 September 2006 10:52, "Mark Haney" <mhaney@ercbroadband.org> 
> wrote about '[gentoo-amd64] Strange ssh behaviour':
>   
>> [N]ow, when I ssh into the box, I
>> get no output from any commands.  su,ls,cat all just return to the
>> prompt without showing me any output.
>>     
>
> Try running strace on a command on the remote side -- see if that indicates 
> anything.
>
>   
I'm curious as to how to do that if no commands run from inside that 
session?


-- 
Mark Haney
Sr. Systems Administrator	
ERC Broadband


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Re: [gentoo-amd64] Strange ssh behaviour

[Boyd Stephen Smith Jr.]

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On Thursday 28 September 2006 15:48, "Mark Haney" <mhaney@ercbroadband.org> 
wrote about 'Re: [gentoo-amd64] Strange ssh behaviour':
> Boyd Stephen Smith Jr. wrote:
> > On Thursday 28 September 2006 10:52, "Mark Haney"
> > <mhaney@ercbroadband.org>
> > wrote about '[gentoo-amd64] Strange ssh behaviour':
> >> [N]ow, when I ssh into the box, I
> >> get no output from any commands.  su,ls,cat all just return to the
> >> prompt without showing me any output.
> > Try running strace on a command on the remote side -- see if that
> > indicates anything.
> I'm curious as to how to do that if no commands run from inside that
> session?

Well, you say the commands run, they just don't produce any output.  I'm 
hoping strace will be different (although, that is a bit unlikely).

In any case, it looks like your shell is have problems exec()-ing commands 
while env and echo are probably built-ins.

Perhaps your nproc ulimit is to low... or maybe it's something entirely 
different.

Try:
ssh host strace ls
ssh host exec ls
ssh host exec strace ls

And see which ones produce output and how the outputs differ.  With the 
outputs if you need any more assistance.

-- 
"If there's one thing we've established over the years,
it's that the vast majority of our users don't have the slightest
clue what's best for them in terms of package stability."
-- Gentoo Developer Ciaran McCreesh

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Re: [gentoo-amd64] Strange ssh behaviour

[felix]

On Thu, Sep 28, 2006 at 11:52:18AM -0400, Mark Haney wrote:
> This might be a bit off topic, but I'm at my wits' end.  I have a server
> that uses PAM/LDAP for authentication.  A recent update broke PAM and
> took me a couple of days to fix.  But now, when I ssh into the box, I
> get no output from any commands.  su,ls,cat all just return to the
> prompt without showing me any output.  I can env and echo fine and tab
> completion works, so I know the shell is okay.  I just don't have any
> clue on what to try next.

Just in case, I will mention a bug I encountered a month or two back.
I could ssh into a machine to run commands, ie ssh ls -l worked, but I
could not ssh in to get an interactive login shell.  It turns out that
app-accessibility/sphinx3 was installing a bogus libutil in /usr/lib,
overriding the real glibc libutil in /lib, and borking everything.
See bug #145667 for details.  The workaround has been to replace the
bogus libs with symlinks to the real ones.

This does not sound like your problem, but I figure it can't hurt to
at least throw it out for you to throw away :-)

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