OMSA: Web UI fails to load when the hostname contains an underscore character

Summary: These are the instructions for restoring access to the OpenManage Server Administrator (OMSA) web interface on a server with an underscore in its hostname.

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Symptoms

The OMSA web interface is inaccessible on a server where the hostname contains an underscore.

For example, the hostname of the server is "FS_1.domain.local."

The message received is usually "This site can't be reached" or "ERR_CONNECTION_CLOSED."

The DSM SA Connection Service is running and listening for connections on port 1311 as expected.

Cause

Underscores are not a valid character for Domain Name System (DNS) hostnames, as documented in RFC 1912.

https://datatracker.ietf.org/doc/html/rfc1912#section-2.1This hyperlink is taking you to a website outside of Dell Technologies.

As a result, OMSA is unable to generate a self-signed certificate during installation and starts its services without a valid TLS configuration. The connection service still runs and binds to port 1311 during startup but does not accept connections.

Resolution

Option A
Change the name of the server to a new name that only contains letters, numbers, or hyphens, then uninstall and reinstall OMSA.
 
Option B
Install a valid certificate and access OMSA by IP address instead of by hostname. Running the following OMConfig command on the affected server creates a new self-signed certificate:

omconfig preferences webserver attribute=gennewcert cn=<servername> org=Dell ou=ESG location=RoundRock state=TX country=US validity=3650 keysize=2048 algorithm=SHA512 webserverrestart=true

 
Replace "<servername>" with any supported value. The simplest option is to use the server's current name with any underscores removed.

Affected Products

OpenManage Server Administrator
Article Properties
Article Number: 000221443
Article Type: Solution
Last Modified: 10 Apr 2025
Version:  4
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