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Bug#458154: network-console: long time-out time during install



On Monday 07 January 2008, Wouter Verhelst wrote:
> > Would the following text be OK for the installation guide (to be added
> > as a note in the network-console section)?
> >
> > <snip>
> > The <command>ssh</command> server in the installer uses a default
> > configuration that does not have a timeout set.
>
> "keepalive" is not the same thing as "timeout".

I'm aware of that. From a user PoV it still looks as a timeout though, 
whether caused by SSH or e.g. NAT.

I see such "timeouts" myself when connecting e.g. to Debian servers, and 
until this discussion I never really understood what caused them. Now that 
is clear.

So maybe we should make explicit that this issue is most likely to happen if 
there is NAT anywhere between the system being installed and the client.

With the comments from Colin, that would result in the following text:

<snip>
The <command>ssh</command> server in the installer uses a default
configuration that does not send keep-alive packets. In principle,
a connection to the system being installed should be kept open
indefinitely. However, in some situations &mdash; depending on your
local network setup &mdash; the connection may be lost after some                     
period of inactivity. One common case where this may happen is when
there is some form of Network Address Translation (NAT) somewhere
between the client and the system being installed. Depending on at
which point of the installation the connection was lost, you may or
may not be able to resume the installation after reconnecting.

</para><para>

You may be able to avoid the connection being dropped by adding the option
<userinput>-o 
ServerAliveInterval=<replaceable>value</replaceable></userinput>
when starting the <command>ssh</command> connection, or by adding that
option in your <command>ssh</command> configuration file. Note however
that in some cases adding this option may also <emphasis>cause</emphasis>
a connection to be dropped (for example if keep-alive packets are sent
during a brief network outage, from which <command>ssh</command> would
otherwise have recovered), so it should only be used when needed.
</snip>

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