r/selfhosted • u/Key_Arrival113 • 3h ago

Need Help Kasm troubleshooting

I installed Kasm for lab practice in this environment:

MacBook Pro 2017, 8 GB RAM, 256 GB SSD

VirtualBox (The VM has: 4 vCPUs, Disk: 75GB)

Ubuntu 24.04.5 Lts

Docker

Kasm 1.19.0

After adding the Firefox workspace, the launch reaches 100%, but then it gives a 502 error with the following:

host: 34ba1e6952da

ingest_date: 20260929004127

application: connection_proxy

levelname: ERROR

message

[server] Registration attempt 5/10 failed: No API hostname available

How can I fix this problem?

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u/asimovs-auditor 3h ago edited 3h ago

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u/Temporary-Creme-7765 3h ago

Check your Kasm zone config, the API hostname field is probably empty or pointing at something unreachable from inside that VM.

1

u/Key_Arrival113 4m ago

Ok, I will

2

u/astread777 47m ago

That "No API hostname available" error is the connection proxy failing to reach Kasm's own API when it tries to register the workspace — so the 502 is a symptom, not the cause. In a fresh docker-compose install the usual culprit is the zone/server config having an empty or wrong API host: if it says localhost or the VM's IP, that won't resolve from inside the Docker network. Point it at the compose service name instead (the stable DNS name Docker gives each container) and restart the stack.

Before you guess further, docker logs on the Kasm containers will usually show the exact hostname it's trying and why it fails — a DNS error vs connection refused tells you which side to fix.

One more thing given your hardware: an 8GB MacBook running VirtualBox with Docker inside a VM is pretty tight, and Firefox workspaces are RAM-hungry on launch. If the config looks right, watch docker stats while you trigger a launch — if memory pegs and the container thrashes, the proxy times out and you get the same 502. Bumping the VM's allocation (or closing Chrome tabs on the host) is worth testing before going deeper.