If you are trying to configure the SFTP Server on SDDC Manager in VCF, you are pretty sure that your SFTP server works fine, but in SDDC you can see an error similar to that:Validation failed for directory <path> on server <FQDN or IP>. Please make sure backup directory is intact and sftp server has write permissions on backup path.
That post may be for you.
Solution:
In my case the root cause of that issue was that my SFTP Server was using too new version of OpenSSH. Yes, too new for SDDC š
In the OpenSSH release 8.8, a crucial change was made:This release disables RSA signatures using the SHA-1 hash algorithm by default. This change has been made as the SHA-1 hash algorithm is cryptographically broken (source).
Check OpenSSH version on your SFTP Server:
Ok, so let’s check what we can see in the SDDC Manager logs.
1. Open SSH session to SDDC Manager and log into vcf account (name of the account depends on bringup configuration but usually it is vcf).
2. Go to log location:cd /var/log/vmware/vcf/operationsmanager
and grep log sile searching ssh-rsa using command:grep -I ssh-rsa operationsmanager.log
In the output we can see that SDDC Manager still tries to use deprecated signature.
The solution is to change the SSH config on the SFTP server to allow the ssh-rsa signature. My SFTP was deployed on the Ubuntu server, so I had to change /etc/ssh/sshd_config and add those lines:HostKeyAlgorithms=+ssh-rsa
PubkeyAcceptdAlgorithms=+ssh-rsa
Then SSH service restart and backup configuration on SDDC Manager works!
BlanketVM 