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David Fletcher 12-03-2010 06:39 PM

ssh connections stopped working
 
This is driving me nuts!

In my home network I have a server running Ubuntu Server, my own desktop
and my son's desktop. Both desktops and my laptop are running Maverick.

I just built him a new PC which we hoped to get set up tonight but I
can't get the data off the HDD in his current one. I want to use rsync
across the network to copy everything to a HDD in either my desktop or
the server I don't care which, but it just won't go.

I know for sure that rsync used to work with his machine because there
is a previous backup on it that was done using rsync from my desktop to
his.

Tonight, I can ssh into the server no problem from my desktop, ping to
his desktop works but ssh both to and from his desktop just fails and
times out.

Nobody has installed firewalls on anything, so I just don't know where
to start.

Curiously, I am sure the laptop also used to be able to ssh into the
server via the WiFi but now does not. Same time out message.

By switching some cables I have eliminated the possibility of the router
blocking port 22.

Can anybody give me a clue, please?

Dave



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Colin Law 12-03-2010 07:03 PM

ssh connections stopped working
 
On 3 December 2010 19:39, David Fletcher <dave@thefletchers.net> wrote:
> This is driving me nuts!
>
> In my home network I have a server running Ubuntu Server, my own desktop
> and my son's desktop. Both desktops and my laptop are running Maverick.
>
> I just built him a new PC which we hoped to get set up tonight but I
> can't get the data off the HDD in his current one. I want to use rsync
> across the network to copy everything to a HDD in either my desktop or
> the server I don't care which, but it just won't go.
>
> I know for sure that rsync used to work with his machine because there
> is a previous backup on it that was done using rsync from my desktop to
> his.
>
> Tonight, I can ssh into the server no problem from my desktop, ping to
> his desktop works but ssh both to and from his desktop just fails and
> times out.
>
> Nobody has installed firewalls on anything, so I just don't know where
> to start.
>
> Curiously, I am sure the laptop also used to be able to ssh into the
> server via the WiFi but now does not. Same time out message.
>
> By switching some cables I have eliminated the possibility of the router
> blocking port 22.
>
> Can anybody give me a clue, please?

Is openssh-server installed?

Have a look in auth.log to see if anything is logged there when you
try to connect via ssh. Are specifying a valid username to ssh when
you try to connect?
ssh -l username server

Colin

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David Fletcher 12-03-2010 08:16 PM

ssh connections stopped working
 
On Fri, 2010-12-03 at 20:03 +0000, Colin Law wrote:
> > Can anybody give me a clue, please?
>
> Is openssh-server installed?
Yes, it's been installed from day 1. Otherwise the previous rsync
operations couldn't have worked.

>
> Have a look in auth.log to see if anything is logged there when you
> try to connect via ssh. Are specifying a valid username to ssh when
> you try to connect?
> ssh -l username server
No, it's not adding entries to auth.log. I know that I have a valid
username. It's the same as in the scripts that I was using to do rsync
operations before. It was all set up and working with my public key
added to .ssh/authorized_keys.

Because I've not looked at this file before, I connected by ssh to the
server and checked it there. Why does it have at the end of the accepted
password line
port 52144 ssh2 ?
I thought ssh worked over port 22? Or am I showing my ignorance here? Is
port 52144 just used to do the authorisation? I guess it negotiates a
random port number for this because next time is was 37747.
Currently the last line in the server auth.log is:-
pam_unix(sshd:session): session opened for user administrator by (uid=0)

>
> Colin
>

Don't suppose it's got anything to do with this but the desktop machine
has been upgraded from Lucid to Maverick. The laptop though was a wipe
and fresh install.

Dave



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Colin Law 12-03-2010 08:29 PM

ssh connections stopped working
 
On 3 December 2010 21:16, David Fletcher <dave@thefletchers.net> wrote:
> On Fri, 2010-12-03 at 20:03 +0000, Colin Law wrote:
>> > Can anybody give me a clue, please?
>>
>> Is openssh-server installed?
> Yes, it's been installed from day 1. Otherwise the previous rsync
> operations couldn't have worked.

Possibly worth re-installing in case it has got mislaid along the way somewhere.
Perhaps the server is not starting for some reason. There might be
something in the messages on startup.

>
>>
>> Have a look in auth.log to see if anything is logged there when you
>> try to connect via ssh.

Reaching the end of my knowledge base here, but I assume that the fact
that there is nothing logged means that it is not an authorization
problem. It suggests the problem is earlier than that. Other than
that I don't think I can help much. Over to someone with more
in-depth knowledge?

Colin

>> *Are specifying a valid username to ssh when
>> you try to connect?
>> ssh -l username server
> No, it's not adding entries to auth.log. I know that I have a valid
> username. It's the same as in the scripts that I was using to do rsync
> operations before. It was all set up and working with my public key
> added to .ssh/authorized_keys.
>
> Because I've not looked at this file before, I connected by ssh to the
> server and checked it there. Why does it have at the end of the accepted
> password line
> port 52144 ssh2 ?
> I thought ssh worked over port 22? Or am I showing my ignorance here? Is
> port 52144 just used to do the authorisation? I guess it negotiates a
> random port number for this because next time is was 37747.
> Currently the last line in the server auth.log is:-
> pam_unix(sshd:session): session opened for user administrator by (uid=0)
>
>>
>> Colin
>>
>
> Don't suppose it's got anything to do with this but the desktop machine
> has been upgraded from Lucid to Maverick. The laptop though was a wipe
> and fresh install.
>
> Dave
>
>
>

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David Fletcher 12-03-2010 09:05 PM

ssh connections stopped working
 
On Fri, 2010-12-03 at 21:29 +0000, Colin Law wrote:

> Reaching the end of my knowledge base here, but I assume that the fact
> that there is nothing logged means that it is not an authorization
> problem. It suggests the problem is earlier than that. Other than
> that I don't think I can help much. Over to someone with more
> in-depth knowledge?
>
> Colin
>

The answer should have been staring me in the face - ping [name of son's
desktop] was working but actually returning the address of somebody
outside!

Now, I think I may know what happened here - I think I may have upgraded
my desktop from Hardy to Maverick with a fresh HDD since the last rsync
to my son's desktop was run. The stuff I needed to restore also gets
backed up to the server, which is where I think I restored it from, so,

SILLY ME

I hadn't put the son's computer back into /etc/hosts!

Thanks Colin for your suggestions they helped me get it sorted out.

Dave



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Colin Law 12-04-2010 08:27 AM

ssh connections stopped working
 
On 3 December 2010 22:05, David Fletcher <dave@thefletchers.net> wrote:
>
> I hadn't put the son's computer back into /etc/hosts!

I find that I do not need to put computers on the local network into
/etc/hosts. If the computer name is piglet then I can just use
piglet.local. I must admit though that I am not sure what it is that
provides this capability.

Colin

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Tom H 12-04-2010 08:33 AM

ssh connections stopped working
 
On Sat, Dec 4, 2010 at 4:27 AM, Colin Law <clanlaw@googlemail.com> wrote:
> On 3 December 2010 22:05, David Fletcher <dave@thefletchers.net> wrote:
>>
>> I hadn't put the son's computer back into /etc/hosts!
>
> I find that I do not need to put computers on the local network into
> /etc/hosts. *If the computer name is piglet then I can just use
> piglet.local. *I must admit though that I am not sure what it is that
> provides this capability.

avahi

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Colin Law 12-04-2010 08:56 AM

ssh connections stopped working
 
On 4 December 2010 09:33, Tom H <tomh0665@gmail.com> wrote:
> On Sat, Dec 4, 2010 at 4:27 AM, Colin Law <clanlaw@googlemail.com> wrote:
>> On 3 December 2010 22:05, David Fletcher <dave@thefletchers.net> wrote:
>>>
>>> I hadn't put the son's computer back into /etc/hosts!
>>
>> I find that I do not need to put computers on the local network into
>> /etc/hosts. *If the computer name is piglet then I can just use
>> piglet.local. *I must admit though that I am not sure what it is that
>> provides this capability.
>
> avahi

Excellent, thanks for that. Looking it up has lead me to discover the
command avahi-browse to show connected machines. Specifically
avahi-browse -at
How did I survive without it?
Oh dear, I seem to have engaged blog mode. Sorry.

Colin

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David Fletcher 12-04-2010 12:20 PM

ssh connections stopped working
 
On Sat, 2010-12-04 at 09:27 +0000, Colin Law wrote:
> On 3 December 2010 22:05, David Fletcher <dave@thefletchers.net> wrote:
> >
> > I hadn't put the son's computer back into /etc/hosts!
>
> I find that I do not need to put computers on the local network into
> /etc/hosts. If the computer name is piglet then I can just use
> piglet.local. I must admit though that I am not sure what it is that
> provides this capability.
>
> Colin
>

Colin,

That is very useful indeed!

I just installed Maverick on the boy's new PC and now I don't need to
set up host addresses or fixed IP addresses to connect - rsync is now
happily sending his files back onto his new PC without doing either.

If I hadn't been a silly billy yesterday I'd never have learned about
this.

Thanks

Dave



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user1 12-04-2010 02:36 PM

ssh connections stopped working
 
On Fri, 03 Dec 2010 19:39:41 +0000, David Fletcher wrote:

> This is driving me nuts!

http://avahi.org/wiki/WikiStart


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