Hi Community,
I have purchased 2 VPS servers and a Load Balancer from OVH. After deploying cPanel on my first VPS, I configured and tested my load balancer, but I encountered the following error: Error 503: Backend unavailable. This type of error typically occurs due to server unavailability behind the IP Load Balancing.
here is curl:
Result of the curl test: (curl - Ilvk "URL")
Error 503: server unavailable
* {
font-family: « Trebuchet MS », « Arial », « Lucida grande », « Bitstream Charter », « Liberation sans », « FreeSans », sans-serif;
font-size: 16px;
line-height: 20px;
color: #494949;
padding: 0;
margin: 0;
font-size: normal;
font-weight: 200;
}
body { background-color: #F1F1F1; padding-top: 95px; }
.container { padding: 0; margin: 0 auto; max-width: 737px; text-align: center; }
.block { display: block; }
.blue { color: #3267BF; }
.regular { font-weight: 400; }
.fs30 { font-size: 30px; line-height: 30px; }
.fs40 { font-size: 40px; line-height: 40px; }
.fs50 { font-size: 50px; line-height: 50px; }
.lh45 { line-height: 45px; }
Error 503: Backend unavailable
This type of error usually results of an unavailability of servers behind IP Load Balancing.
here is nmap -Pn on the backend server:
Result of the nmap test on the Backend: (nmap -Pn "ip_du_backend"):
Starting Nmap 7.94 ( https://nmap.org ) at 2023-09-16 13:33 Greenwich Standard Time
Nmap scan report for vps-1cacc0d9.vps.ovh.net (141.94.68.128)
Host is up (0.13s latency).
Not shown: 930 filtered tcp ports (no-response), 58 closed tcp ports (reset)
PORT STATE SERVICE
21/tcp open ftp
25/tcp open smtp
53/tcp open domain
80/tcp open http
110/tcp open pop3
143/tcp open imap
443/tcp open https
465/tcp open smtps
587/tcp open submission
993/tcp open imaps
995/tcp open pop3s
3306/tcp open mysql
Nmap done: 1 IP address (1 host up) scanned in 6.84 seconds
Result of the iptable command on the backend: (iptables -L):
Error message:
login as: ubuntu
ubuntu@141.94.68.128's password:
login as: ubuntu
ubuntu@141.94.68.128's password:
Welcome to Ubuntu 20.04.6 LTS (GNU/Linux 5.4.0-162-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
System information as of Sat Sep 16 11:07:54 UTC 2023
System load: 0.05 Processes: 291
Usage of /: 17.8% of 154.88GB Users logged in: 0
Memory usage: 5% IPv4 address for ens3: 141.94.68.128
Swap usage: 0%
* Strictly confined Kubernetes makes edge and IoT secure. Learn how MicroK8s
just raised the bar for easy, resilient and secure K8s cluster deployment.
https://ubuntu.com/engage/secure-kubernetes-at-the-edge
Expanded Security Maintenance for Applications is not enabled.
26 updates can be applied immediately.
To see these additional updates run: apt list --upgradable
46 additional security updates can be applied with ESM Apps.
Learn more about enabling ESM Apps service at https://ubuntu.com/esm
Last login: Fri Sep 15 10:16:03 2023 from 197.239.80.129
ubuntu@141-94-68-128:~$ sodo -i
WARNING:root:could not open file '/etc/apt/sources.list.d/cpanel-plugins.list'
Command 'sodo' not found, did you mean:
command 'nodo' from snap nodo (master)
command 'sudo' from deb sudo (1.8.31-1ubuntu1.5)
command 'sudo' from deb sudo-ldap (1.8.31-1ubuntu1.5)
command 'todo' from deb devtodo (0.1.20-7build1)
See 'snap info ' for additional versions.