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Remove a line from a file using sed (useful for updating known SSH server keys when they change)

Terminal - Remove a line from a file using sed (useful for updating known SSH server keys when they change)
sed '${LINE}d' ~/.ssh/known_host
2012-01-16 18:00:12
User: lucasrangit
Functions: sed
-5
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Remove a line from a file using sed (useful for updating known SSH server keys when they change)

When you SSH to a server who's hostname or IP has changed since the last time a connection was recorded in the known_hosts file a warning will be displayed since this indicated a possible DNS spoofing attack. If this is a known change then this command will remove the previous entry and allow the SSH connection. The SSH client will prompt you as if it was the first time connected to the server.

Replace ${LINE} with the line of the offending key in ~known_hosts. 49 in the sample output.

Show sample output | Add to favourites | Report as malicious

Alternatives

There are 3 alternatives - vote for the best!

Terminal - Alternatives
ssh-keygen -R <thehost>
2012-01-16 21:07:44
User: bunam
Functions: ssh ssh-keygen
15
Up
Down
Remove a line from a file using sed (useful for updating known SSH server keys when they change)

remove the host for the .ssh/know_host file

Comments (1) | Add to favourites | Report as malicious
sed -i '${LINE}d' ~/.ssh/known_host
2012-01-19 11:22:45
User: richard
Functions: sed
5
Up
Down
Remove a line from a file using sed (useful for updating known SSH server keys when they change)
Comments (3) | Add to favourites | Report as malicious
vi +<lineNumber>d +wq <filename>
2012-01-25 18:28:03
User: detert
Functions: vi
1
Up
Down
Remove a line from a file using sed (useful for updating known SSH server keys when they change)

For example, to remove line 5 from foo, type: vi +5d +wq foo

Comments (1) | Add to favourites | Report as malicious
perl -p -i -e 's/.*\n//g if $.==2' ~/.ssh/known_hosts
2012-01-17 14:11:03
User: meappy
Functions: perl
Tags: ssh perl known_hosts
-1
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Remove a line from a file using sed (useful for updating known SSH server keys when they change)

Easily removes line #2 in ~/.ssh/known_hosts.

Show sample output | Comments (0) | Add to favourites | Report as malicious

Know a better way?

If you can do better, submit your command here.

What others think

To remove a line in know_hosts file you can also do

ssh-keygen -R www.example.com
Comment by gilles 69 weeks and 6 days ago

That doesn't actually leave you with an ~/.ssh/know_host file with the line removed anyway.

Comment by DaveQB 68 weeks and 1 day ago

I went for

mv ~/.ssh/known_hosts ~/.ssh/known_hosts.old; sed "${LINE}d" ~/.ssh/known_hosts.old > ~/.ssh/known_hosts

... because not only does ssh-keygen silently fail with the -R option on my (ooooold) system, but sed doesn't know -i either ...

Comment by assarbad 63 weeks and 4 days ago

Your point of view

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