VAMI SFTP backup fails with error "General system error reported by backup server"

Products

• VMware vCenter Server

Issue/Introduction

• SFTP backup configuration fails with error "General system error reported by backup server"
• vCenter connects successfully to the SFTP server through CLI (ssh -vvv <backup_user>@<SFTP_IP>)
• Errors similar to the following example can be seen in the appliance management log (/var/log/vmware/applmgmt/applmgmt.log):

  YYYY-MM-Date [3154]INFO:plugins.SftpStorageIOLib:Executing command to get remote root: ssh -q -p 22 -i /root/.ss
  h/id_rsa -o UserKnownHostsFile=/root/.ssh/br_temp_known_hosts 'backup_user@sftp_ip' echo ~
  2025-06-19T04:15:16 AM UTC [3154]INFO:plugins.SftpStorageIOLib:Authorizing localhost with command sshpass -f /tmp/tmpsnksqb9k
  ssh-copy-id -i /root/.ssh/id_rsa.pub -p 22 -o UserKnownHostsFile=/root/.ssh/br_temp_known_hosts backup_user@sftp_ip
  YYYY-MM-Date [3154]ERROR:plugins.SftpStorageIOLib:Failed to authorize local host with command: sshpass -f /tmp/tmpsnksqb9k ssh-copy-id -i /root/.ssh/id_rsa.pub -p 22 -o UserKnownHostsFile=/root/.ssh/br_temp_known_hosts backup_user@sftp_ip. Will proceed with backup through curl
  YYYY-MM-Date [3154]INFO:plugins.SftpStorageIOLib:Executing command to get remote root: ssh -q -p 22 -i /root/.ss
  h/id_rsa -o UserKnownHostsFile=/root/.ssh/br_temp_known_hosts 'backup_user@sftp_ip' echo ~
  YYYY-MM-Date [3154]DEBUG:plugins.SftpStorageIOLib:Passwordless ssh tunnel is not working, falling back to CURL
  YYYY-MM-Date [3154]ERROR:plugins.FtpStorageIOLib:sftp cmd failed. RC: 22, Err: curl: (22) The requested URL returned error: 502
  , Cmd: ['/usr/bin/curl', '--fail', '-u', 'BACKUP_USER:****', '--connect-timeout', '120', '--ssl-reqd', '-k', '--proxy',
  'http://PROXY_IP:8080/', '--proxytunnel', '--silent', '--show-error', '--list-only', 'sftp://SFTP_IP:22/data/vcsa/']

Environment

• VMware vCenter Server 7.0.x
• VMware vCenter Server 8.0.x

Cause

This issue is encountered when the vCenter Server tries to (unsuccessfully) establish the SSH connection with the SFTP backup server using a configured proxy.

Resolution

To solve this issue, add the FQDN and the IP address of the SFTP backup server to the NO_PROXY rule in the proxy configuration of the vCenter Server Appliance:

1. Open an SSH connection to the vCenter Server Appliance and log in as the 'root' user.
2. Create a backup of the proxy configuration file:

   # cp /etc/sysconfig/proxy /etc/sysconfig/proxy.bak

3. Edit the file using the VI editor:

   # vi /etc/sysconfig/proxy

4. Add both the IP address and the FQDN of the SFTP server as additional entries in the NO_PROXY option:

   Example:
   
   NO_PROXY="localhost, 127.0.0.1, <SFTP_IP>, <SFTP_FQDN>"

5. Restart the vCenter Services:

   # service-control -- stop --all && service-control --start --all

Additional Information

In some situations, restarting the services might not apply the configuration changes. If the issue persists after the restart, reboot the entire VCSA.