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[BUG] kasm_manager has no healthcheck start_period, so a cold start leaves kasm_proxy created but never started #103
Description
Is there an existing issue for this?
- I have searched the existing issues
Current Behavior
On a cold start, kasm_manager reports unhealthy before it has finished starting. Since the Dockerfile makes proxy depend on it with condition: service_healthy, compose aborts the whole up:
Container kasm_api Healthy
Container kasm_manager Error dependency kasm_manager failed to start
dependency failed to start: container kasm_manager is unhealthy
s6-rc: warning: unable to start service svc-kasm: command exited 1
proxy is left in created and never started, and so is kasm_rdp_https_gateway, which the Dockerfile makes depend on proxy:
NAMES STATUS PORTS
kasm_rdp_https_gateway Created
kasm_proxy Created
kasm_rdp_gateway Up 18 seconds (health: starting) 0.0.0.0:3389->3389/tcp
kasm_agent Up 12 minutes (healthy)
kasm_api Up 12 minutes (healthy)
kasm_manager Up 12 minutes (healthy) <-- healthy, but too late
kasm_guac Up 12 minutes (unhealthy)
kasm_db Up 12 minutes (healthy)
kasm_manager becomes healthy seconds later, but svc-kasm is a oneshot, so nothing runs /opt/kasm/bin/start again and the container stays half started indefinitely. The installation wizard on port 3000 answers, because it runs in the outer container, while KASM_PORT is dead. Running docker exec kasm /opt/kasm/bin/start by hand fixes it immediately, since the dependency is satisfied by then.
This is what I believe is the cause. The Dockerfile gates proxy on both kasm_manager and kasm_api being healthy:
# Fix dependencies so containers start in the right order
yq -i '.services.proxy.depends_on = {"kasm_manager":{"condition": "service_healthy"},"kasm_api":{"condition": "service_healthy"}, ...}'and then gives a healthcheck grace period to kasm_api only:
yq -i '.services.kasm_api.healthcheck += {"start_period": "60s","start_interval": "30s"}'kasm_manager is gated the same way but keeps the stock healthcheck, with no grace period suited to being used as a startup gate. That matters because compose only aborts a service_healthy wait when the dependency reports unhealthy — while it reports starting it waits indefinitely (pkg/compose/convergence.go):
case container.Healthy: // continue
case container.Unhealthy: return false, fmt.Errorf("container %s is unhealthy", name)
case container.Starting: return false, nil // keep waitingSo a start_period on kasm_manager is exactly what turns this failure into a successful wait.
One more consequence worth mentioning: this fails completely silently behind a reverse proxy that uses Docker service discovery. Traefik's Docker provider skips any container whose health is not healthy (pkg/provider/docker/config.go) without logging anything, so Kasm simply never gets a route and there is no error anywhere to point at the real problem.
Expected Behavior
kasm_manager should stay in starting until it is genuinely ready, so that compose waits for it instead of aborting, and all Kasm services should be started after a cold start without any manual intervention.
Steps To Reproduce
- Deploy
linuxserver/kasmon a host wherekasm_managertakes longer thaninterval x retriesto become ready, and complete the installation wizard. - Recreate the container (
docker compose up -d --force-recreate, or reboot the host). - Watch
docker logs kasm: the startup ends withdependency failed to start: container kasm_manager is unhealthyfollowed bys6-rc: warning: unable to start service svc-kasm: command exited 1. - Run
docker exec kasm docker ps -a:kasm_proxyandkasm_rdp_https_gatewayare increated, whilekasm_manageris healthy. https://<host>:3000(wizard) answers,https://<host>:<KASM_PORT>does not.- Run
docker exec kasm /opt/kasm/bin/start: everything starts and works, until the next recreation.
Reproduces on every recreation of the container.
Environment
- OS: Debian 13 (Proxmox 9.2.6 VM)
- How docker service was installed: from Docker's official APT repository (download.docker.com)CPU architecture
x86-64
Docker creation
Deployed through Ansible, which renders this compose file (domain replaced with a placeholder). The Traefik labels and the external network are not related to the failure — it is triggered by the container being recreated, whatever else is in the file.
services:
application:
container_name: kasm
image: linuxserver/kasm
restart: unless-stopped
privileged: true
stop_grace_period: "90s"
healthcheck:
test: ["CMD-SHELL", "curl --silent --head --insecure --retry 1 https://localhost:3000 && curl --silent --head --insecure --retry 1 https://localhost:84"]
interval: 30s
timeout: 30s
start_period: 0s
retries: 3
environment:
PUID: "1000"
PGID: "1000"
TZ: "Europe/Paris"
KASM_PORT: "84"
volumes:
- "data:/opt:rw"
- "profiles:/profiles:rw"
ports:
- "83:3000"
- "84:84"
labels:
traefik.enable: "true"
traefik.http.services.Kasm_application.loadbalancer.server.port: "84"
traefik.http.services.Kasm_application.loadbalancer.server.scheme: https
traefik.http.services.Kasm_application.loadbalancer.serverstransport: insecure_HTTPS_backend@file
traefik.http.routers.Kasm_application.service: Kasm_application
traefik.http.routers.Kasm_application.rule: Host(`kasm.example.com`)
traefik.http.routers.Kasm_application.entrypoints: websecure
traefik.http.routers.Kasm_application.middlewares: no_index@file
networks:
- "DMZ"
volumes:
data:
profiles:
networks:
DMZ:
external: true
name: DMZContainer logs
[migrations] started
[migrations] no migrations found
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GID/UID
───────────────────────────────────────
User UID: 1000
User GID: 1000
───────────────────────────────────────
Linuxserver.io version: 1.19.0-ls139
Build-date: 2026-07-14T22:37:23+00:00
───────────────────────────────────────
[custom-init] No custom files found, skipping...
time="2026-08-04T14:08:54+02:00" level=error msg="+ echo '[ENTRYPOINT] STARTED'" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:54+02:00" level=info msg="[ENTRYPOINT] STARTED" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:54+02:00" level=error msg="+ SOCKET_PATH=/run/docker/plugins/kasmlogger.sock" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:54+02:00" level=error msg="+ '[' -e /run/docker/plugins/kasmlogger.sock ]" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:54+02:00" level=info msg="[ENTRYPOINT] Launching plugin.py..." plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:54+02:00" level=error msg="+ echo '[ENTRYPOINT] Launching plugin.py...'" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:54+02:00" level=error msg="+ export 'PATH=/opt/venv/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:54+02:00" level=error msg="+ sleep 5" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:54+02:00" level=error msg="+ python3 /plugin.py" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:55+02:00" level=info msg=" * Serving Flask app 'plugin'" plugin=88b6cf90a0cbf477347339d8e2dee30399e3f3034109890dff92f757d8290518
time="2026-08-04T14:08:55+02:00" level=info msg=" * Debug mode: off" plugin=88b6cf90a0cbf477347339d8e2dee30399e3f3034109890dff92f757d8290518
time="2026-08-04T14:08:55+02:00" level=info msg=" * Serving Flask app 'plugin'" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:55+02:00" level=info msg=" * Debug mode: off" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
Pulling Latest Kasm Service Images
time="2026-08-04T14:08:56+02:00" level=warning msg="/opt/kasm/1.19.0/docker/docker-compose.yaml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion"
Image kasmweb/proxy:1.19.0-rolling Pulling
Image kasmweb/api:1.19.0-rolling Pulling
Image kasmweb/kasm-guac:1.19.0-rolling Pulling
Image kasmweb/rdp-https-gateway:1.19.0-rolling Pulling
Image kasmweb/postgres:1.19.0-rolling Pulling
Image kasmweb/manager:1.19.0-rolling Pulling
Image kasmweb/rdp-gateway:1.19.0-rolling Pulling
Image kasmweb/agent:1.19.0-rolling Pulling
Image kasmweb/rdp-https-gateway:1.19.0-rolling Pulled
Image kasmweb/manager:1.19.0-rolling Pulled
Image kasmweb/rdp-gateway:1.19.0-rolling Pulled
Image kasmweb/agent:1.19.0-rolling Pulled
Image kasmweb/kasm-guac:1.19.0-rolling Pulled
Image kasmweb/proxy:1.19.0-rolling Pulled
Image kasmweb/api:1.19.0-rolling Pulled
Image kasmweb/postgres:1.19.0-rolling Pulled
Upgrading rolling plugins
Inspecting plugin: kasmweb/logger:amd64-1.1-rolling-daily
* Type: log plugin
* Will not update rolling plugin: currently at the latest version
Inspecting plugin: kasmweb/sidecar:amd64-1.5-rolling-daily
* Type: network plugin
* Will not update rolling plugin: currently at the latest version
Starting Kasm Services
time="2026-08-04T14:08:59+02:00" level=warning msg="/opt/kasm/1.19.0/docker/docker-compose.yaml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion"
Container kasm_db Creating
Container kasm_guac Creating
Container kasm_guac Created
Container kasm_db Created
Container kasm_manager Creating
Container kasm_api Creating
Container kasm_manager Created
Container kasm_agent Creating
Container kasm_api Created
Container kasm_rdp_gateway Creating
Container kasm_rdp_gateway Created
Container kasm_agent Created
Container kasm_proxy Creating
Container kasm_proxy Created
Container kasm_rdp_https_gateway Creating
Container kasm_rdp_https_gateway Created
Container kasm_guac Starting
Container kasm_db Starting
Container kasm_guac Started
Container kasm_db Started
Container kasm_db Waiting
Container kasm_db Waiting
time="2026-08-04T14:08:59+02:00" level=error msg="+ echo '[ENTRYPOINT] Checking socket existence...'" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:59+02:00" level=error msg="+ ls -l /run/docker/plugins" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:59+02:00" level=info msg="[ENTRYPOINT] Checking socket existence..." plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:59+02:00" level=info msg="total 0" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:59+02:00" level=info msg="prwx------ 1 root root 0 Aug 4 12:08 4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969-stderr" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:59+02:00" level=info msg="prwx------ 1 root root 0 Aug 4 12:08 4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969-stdout" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:59+02:00" level=info msg="srwxr-xr-x 1 root root 0 Aug 4 12:08 kasmlogger.sock" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:59+02:00" level=error msg="+ '[' '!' -S /run/docker/plugins/kasmlogger.sock ]" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
time="2026-08-04T14:08:59+02:00" level=error msg="+ tail -f /dev/null" plugin=4049a71bc4ba4a1c9b44f3f60e186775aa649737608ffce2490bcd9e03f40969
Container kasm_db Healthy
Container kasm_api Starting
Container kasm_db Healthy
Container kasm_manager Starting
Container kasm_manager Started
Container kasm_agent Starting
Container kasm_api Started
Container kasm_rdp_gateway Starting
Container kasm_agent Started
Container kasm_manager Waiting
Container kasm_api Waiting
Container kasm_rdp_gateway Started
Container kasm_api Healthy
Container kasm_manager Error dependency kasm_manager failed to start
dependency failed to start: container kasm_manager is unhealthy
s6-rc: warning: unable to start service svc-kasm: command exited 1
Activity
Zackey commentedon Aug 5, 2026
Good writeup I had the same issue. I suggest a simple fix is to just repeat /opt/kasm/bin/start about a minute after startup. Whatever else works.
tigerblue77 commentedon Aug 5, 2026
Hi @Zackey, please have a look at the attached PR
Zackey commentedon Aug 8, 2026
im not a githubber @tigerblue77 so dont know how to look at PRs or apply them, sorry :(
rodrigoaantunes commentedon Aug 25, 2026
I have the same problem, how to solve?
tigerblue77 commentedon Aug 25, 2026
It's already merged and fixed from my side. Please update to the latest version
rodrigoaantunes commentedon Aug 25, 2026
I followd this, just right now and the same problem happened
https://hub.docker.com/r/linuxserver/kasm
My docker compose:
services:
kasm:
image: lscr.io/linuxserver/kasm:latest
container_name: kasm
privileged: true
environment:
- KASM_PORT=443
volumes:
- /path/to/kasm/data:/opt
ports:
- 3100:3000
- 443:443
restart: unless-stopped
tigerblue77 commentedon Aug 25, 2026
No idea then, open a new issue ? Or check with Claude code ? 🚀
rodrigoaantunes commentedon Aug 25, 2026
My docker compose:
services:
kasm:
image: lscr.io/linuxserver/kasm:latest
container_name: kasm_server
privileged: true
environment:
- KASM_PORT=443
volumes:
- ./data:/opt
ports:
- "3100:3000"
- "443:443"
restart: unless-stopped
What I did:
docker compose down
docker compose up -d
accessed https://192.168.0.10:3100/
configured the passwords
selected EDGE and install
waited for long time
then got this (snippet):
...
Image kasmweb/kasm-guac:1.19.0-rolling Pulled
Upgrading rolling plugins
Inspecting plugin: kasmweb/logger:amd64-1.1-rolling-daily
Upgrading plugin kasmweb/logger:amd64-1.1-rolling-daily from kasmweb/kasm-logging-plugin:amd64-1.1-rolling-daily to kasmweb/kasm-logging-plugin:amd64-1.1-rolling-daily
amd64-1.1-rolling-daily: Pulling from kasmweb/kasm-logging-plugin
Digest: sha256:e3d555bf0fcb544c12f4570ade1e9689e55a12e6080e15aa282a5575666a0ffa
da0dea094b15: Already exists
da0dea094b15: Complete
Upgraded plugin kasmweb/logger:amd64-1.1-rolling-daily to docker.io/kasmweb/kasm-logging-plugin:amd64-1.1-rolling-daily
Inspecting plugin: kasmweb/sidecar:amd64-1.5-rolling-daily
Upgrading plugin kasmweb/sidecar:amd64-1.5-rolling-daily from kasmweb/kasm-network-plugin:amd64-1.5-rolling-daily to kasmweb/kasm-network-plugin:amd64-1.5-rolling-daily
amd64-1.5-rolling-daily: Pulling from kasmweb/kasm-network-plugin
Digest: sha256:482c0c5428ec354ab870024d62b425408064af9864163d3228ee6dcd3d883757
7b6da3f320f2: Already exists
7b6da3f320f2: Complete
Upgraded plugin kasmweb/sidecar:amd64-1.5-rolling-daily to docker.io/kasmweb/kasm-network-plugin:amd64-1.5-rolling-daily
Starting Kasm Services
time="2026-08-25T18:02:58Z" level=warning msg="/opt/kasm/1.19.0/docker/docker-compose.yaml: the attribute
versionis obsolete, it will be ignored, please remove it to avoid potential confusion"Container kasm_api Creating
Container kasm_guac Creating
Container kasm_manager Creating
Container kasm_api Created
Container kasm_rdp_gateway Creating
Container kasm_manager Created
Container kasm_agent Creating
Container kasm_agent Created
Container kasm_rdp_gateway Created
Container kasm_guac Created
Container kasm_proxy Creating
Container kasm_proxy Created
Container kasm_rdp_https_gateway Creating
Container kasm_rdp_https_gateway Created
Container kasm_db Starting
Container kasm_guac Starting
Container kasm_db Started
Container kasm_db Waiting
Container kasm_db Waiting
Container kasm_guac Started
Container kasm_db Healthy
Container kasm_manager Starting
Container kasm_db Healthy
Container kasm_api Starting
Container kasm_api Started
Container kasm_rdp_gateway Starting
Container kasm_manager Started
Container kasm_agent Starting
Container kasm_agent Started
Container kasm_api Waiting
Container kasm_manager Waiting
Container kasm_rdp_gateway Started
Container kasm_api Error dependency kasm_api failed to start
dependency failed to start: container kasm_api is unhealthy
An error has occurred, please review the log at ./kasm_install_1787680335.log
thespad commentedon Aug 26, 2026
Is it a particularly low spec host or slow storage? If it takes longer than 30 seconds for the container to start it can still cause the dependency chain to fail.
rodrigoaantunes commentedon Sep 2, 2026
That was it, thanks.