Using sed to search and replace exact string.

[Spork Schivago]

Hi!

I am attempting to use sed to change a file. The contents are something like this:

#PasswordAuthentication yes
PasswordAuthentication yes

I want to change the second PasswordAuthentication to no. However, I am having some issues. My sed command is changing both to no.

This is what I've tried

sed -i 's/\<PasswordAuthentication yes/PasswordAuthentication no/g' sshd_config

That changes both.

sed -i "s/\bPasswordAuthentication yes/PasswordAuthentication no/g" sshd_config

That changes both.

sed -i "s/\>PasswordAuthentication yes/PasswordAuthentication no/g" sshd_config

That changes neither.

I guess I'm getting a bit confused about word boundaries. Any ideas what I'm doing wrong and how to accomplish what I'm trying to accomplish?

Thanks!

**EDIT: I believe I found the solution.

sed -i "s/^PasswordAuthentication yes*$/PasswordAuthentication no/g" sshd_config

that seems to change PasswordAuthentication and not #PasswordAuthentication.