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I would like to disable strict host key checking in ssh for ubuntu 11.04. How to do it?

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Hi karthick87, I hope you understand the security implications of making that change ;) –  bodhi.zazen Dec 13 '11 at 16:18
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4 Answers

up vote 27 down vote accepted

In your ~/.ssh/config (if this file doesn't exist, just create it):

Host *
    StrictHostKeyChecking no

This will turn it off for all hosts you connect to. You can replace the * with a hostname pattern if you only want it to apply to some hosts.

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There is no file named config in my home directory. –  karthick87 Dec 14 '11 at 14:40
Make one - the entire contents of the file are in my quote above. Note it's in the .ssh subdirectory of your homedir as well. –  Caesium Dec 14 '11 at 14:44
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Rather than adding it to your ~/.ssh/config file for all Host *, it would be a safer to specify a particular host.

You can also pass a parameter on the command-line like this:

ssh -o StrictHostKeyChecking=no yourHardenedHost.com
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Note that you generally only need to do this once per host since it says this the first time: Warning: Permanently added 'frxxx.blaps.net,' (RSA) to the list of known hosts. –  MarkHu Jul 24 '13 at 0:49
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FYI. I prefer to disable host checking just when using cssh.

alias cssh='cssh -o "-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null"'
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cssh or ssh? –  kenorb Jan 16 at 14:29
Maybe he uses cssh.sourceforge.net –  MarkHu Jan 31 at 3:22
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I don't have the rep yet to comment above - but it's worth pointing out:

StrictHostKeyChecking no

will mean hostkeys are still added to .ssh/known_hosts - you just won't be prompted about whether you trust them, but should hosts change I'm willing to bet you'll get the big warning about it.

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You're correct, you do get the big warning –  Freedom_Ben Jan 20 at 17:35
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