Re: Sed or awk: remove a line from a file
On Fri, 2010-05-28 at 09:19 -0400, John A. Sullivan III wrote:
> On Fri, 2010-05-28 at 14:45 +0200, François TOURDE wrote:
> > Le 14757ième jour après Epoch,
> > Dotan Cohen écrivait:
> >
> > > As I regularly format my test box, I often get stuck SSHing into it, like this:
> > >
> > > $ ssh user@domain
> > > @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
> > > @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
> > > @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
> > > IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
> > > Someone could be eavesdropping on you right now (man-in-the-middle attack)!
> > > It is also possible that the RSA host key has just been changed.
> > > The fingerprint for the RSA key sent by the remote host is
> > > --:--:--:--:--:--:--:--:--:--:--:--:--:--:--:--:--:--:--:--
> > > Please contact your system administrator.
> > > Add correct host key in /home/user/.ssh/known_hosts to get rid of this message.
> > > Offending key in /home/user/.ssh/known_hosts:44
> > > RSA host key for domain has changed and you have requested strict checking.
> > > Host key verification failed.
> > >
> > >
> > >
> > > Now, I need strict checking but I'd like to just remove line 44 from
> > > ~/.ssh/known_hosts. Easy to do in VIM, probably even easier to do in
> > > sed or awk. But I've been reading sed and awk tutorials for two hours
> > > and I cannot figure out how to remove line N from the file without
> > > creating a second file. If I'm already going through the hassle of
> > > creating then moving a second file then I might as well just edit the
> > > file in VIM.
> > >
> > > Any ideas?
> >
> > 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
>
>
>
I might also mention that this is about the only way to do it if you are
using hashed known_hosts files - John
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