Hi!
A colleague of mine uses putty from windows to connect to a linux server. He logs in without giving any password. Now a new linux server has been installed. He copied the .ssh directory from the 1st server to the 2nd one. But when he logs in the 2nd server with the same windows workstation as before, he still needs to give his password.
Shouldn't it work by just coping.ssh from one server to the other? Or did I forget something?
Thanks.

ssh is "secure" shell so requires security. The most common causes of "still neeeding a password" are it isn't secure for one of the following reason:

The account on the target host has no password. If this is the case set the password.

The target user's home directory or .ssh is world writable. ls -ld ~user will give you the permissions of the user's home. Insure there is no w or x for anyone other than the user himself. ls -ld ~user/.ssh will give you the permissions for his .ssh - that should have no permissions for anyone but the user himself.

Using the same ssh setup on two hosts is possible and desirable in cluster scenarios but I would advise against it in most other scenarios. You should create a unique .ssh directory on the target host user then insert the keys from the source host user into the target host user's ~user/.ssh/authorized_keys file to enable trust between them.

Just remember such trusts are valid for anyone who can be the source host user. If someone hacks your source host they will then have a quick way to hack all your targets that consider the source host trusted. Unless you're running scripts from the source to the target I'd recommend NOT setting up trusts. Typing a password isn't really that hard based on the security benefit it provides.

Thanks for your answer. The problem was that .ssh was world writable. Thanks afgain for your help.