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

Products

• VMware vCenter Server

Issue/Introduction

• SFTP backup configuration failed with error "General system error reported by backup server"
• vCenter connects successfully to the SFTP server through CLI (ssh -vvv backup_user@SFTP_IP)
• applmgmt logs - /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 

Cause

The issue is encountered due to the SSH connection failure between the vCenter and the SFTP server through the proxy.

Resolution

 Add the SFTP server to the NO PROXY list of the vCenter proxy settings. 

1. Take an SSH session to the vCenter with root user. 
2. Take a backup of the proxy file - cp /etc/sysconfig/proxy /etc/sysconfig/proxy.bak 
3. Edit the proxy file - vi /etc/sysconfig/proxy 
4. Add the SFTP server IP and FQDN to the NO_PROXY list - 
Example:
NO_PROXY="localhost, 127.0.0.1, SFTP_IP, SFTP_FQDN"    

5. Restart all the services on the vCenter - 
service-control -- stop --all && service-control --start --all