Re: Sed or awk: remove a line from a file
On Fri, 2010-05-28 at 17:38 +0200, Elimar Riesebieter wrote:
> * John A. Sullivan III [100528 11:06 -0400]
> > On Fri, 2010-05-28 at 15:52 +0200, Elimar Riesebieter wrote:
> > > * John A. Sullivan III [100528 09:19 -0400]
> > > > On Fri, 2010-05-28 at 14:45 +0200, François TOURDE wrote:
> > > [...]
> > > > >
> > > > > Don't use sed nor awk...
> > > > >
> > > > > man ssh-keygen say:
> > > > >
> > > > > -R hostname
> > > > > Removes all keys belonging to hostname from a known_hosts file. This option is useful to delete hashed
> > > > > hosts (see the -H option above).
> > > > >
> > > > >
> > > > Yes, exactly. We use that all the time for similar reasons. One caveat
> > > > - if you use a non-standard port (which we regularly do for security
> > > > with such a dangerous application), the host must be specified as
> > > > [hostname]:port, e.g., ssh-keygen -R [comp1.mycompany.com]:222
> > >
> > > How to remove _all_ ip's from hosts with a dynamic IP such as dyndns
> > > hosts?
> > <snip>
> > I'm not sure I understand the question. If you mean how to remove all
> > entries in known_hosts which pertain to hosts with dynamic IP addresses,
> > assuming you know the host name and use the hostname in your ssh
> > command, then you will want to remove the entry by using the hostname
> > and the IP address is not an issue. If there are entries for the IP
> > address and these are causing a problem, then one needs to remove the
> > entry for the IP address. Depending on whether or not there is a custom
> > port, the syntax would be either:
>
> It should not be possible:
>
> Host a.dyn.dns has ip 1.2.3.4
>
> 24 h later:
>
> Host a.dyn.dns has ip 1.2.10.11
> and maybe
> host b.dyn.dns has 1.2.3.4
>
> This information ssh-keygen is missing so it shouldn't be possible
> to
> ssh-keygen -R a.dyn.dns
> and it would remove all ip's this host ever had, isn't it?
I'm not that familiar with the way known_hosts is recorded and all my
known_host files are hashed so I can't look at them (and I am not an ssh
expert by any stretch of the imagination!). However, I thought if one
connect via name, an entry was made using the name and if one connected
via IP address a different entry was made using the IP address. I'm not
100% sure though. Sorry I can't be of more help - John
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