Neil Bothwick starts his day with a big cup of computer conundrums.
Q
That not syncing feeling
I have been using grsync over SSH for years to back up some folders password-less from my main computer to a Netgear ReadyNas Duo V2 without issue. Recently, I decided to do a clean install of Linux Mint after years of rolling updates. When I re-installed grsync and created RSA keys and tried to copy them to the NAS, I started to get connection problems, with errors like:
Unable to negotiate with 192.168.1.106 port 22: no matching host key type found. Their offer:
ssh-rsa rsync: connection unexpectedly closed
Can you please give me some advice on the correct way to set it up?
Ronald Zec
A It looks like reason the connection is failing is that later versions of OpenSSH no longer support RSA keys by default, so if they are disabled on either your computer or the NAS, you will see a message like this. You can get more information by using ssh in a terminal with verbose output: $ ssh -vuser@nas
To see which key algorithms it supports, run: $ ssh -Q HostKeyAlgorithms
If you have SSH terminal access to the NAS, you can use the same command to see which ciphers it supports. Then you can use ssh-keygen to create a suitable key pair acceptable to both. If both sides say they do accept RSA, it may be that your keys are not large enough (smaller is less secure). You can see the minimum accepted size with: $ ssh -Guser@nas| grep requiredrsasize