I would highly recommend migrating to Dockerfile or Railpack as Nixpacks is deprecated.

Thank you! I'm using Nixpacks because Railway auto-detected

it for my Python/Streamlit app.

Could you guide me on how to migrate to Dockerfile or

Railpack for a Streamlit app? Will this fix the volume

mounting issue?

Hi, I think this reply might be for a different thread.

My issue is about Railway Volume not mounting for a

Python/Streamlit app.

Took care of it.

I'm not 100% sure it'll fix the mounting issue, but it might. (As Nixpacks is deprecated).

You can probably get an AI agent (like ChatGPT) to draft up a Dockerfile or a Railpack configuration for you based on your application.

You can refer to Railpack docs at https://railpack.com/getting-started if needed.

Even with Dockerfile detected and ENTRYPOINT set,

Railway seems to be injecting STREAMLIT_SERVER_PORT=$PORT

before our entrypoint runs. The entrypoint never executes.

Custom start command also doesn't help.

Is Railway auto-generating a start command for Streamlit

apps that overrides the Dockerfile ENTRYPOINT?

I'd try using CMD. Also, remove any custom start commands if you have one set.

Thank you! Removed the custom start command and

updated Dockerfile to use CMD instead of ENTRYPOINT.

Redeploying now — will update with results!

Still getting same error after using CMD and removing

custom start command.

Even with ENV STREAMLIT_SERVER_PORT=8080 in Dockerfile,

Railway seems to be overriding it with $PORT (literal string).

Error: Invalid value for '--server.port'

(env var: 'STREAMLIT_SERVER_PORT'): '$PORT' is not a valid integer

Is Railway auto-injecting STREAMLIT_SERVER_PORT=$PORT

for Streamlit apps? How can we prevent this?

What's your CMD command?

CMD ["streamlit", "run", "layout.py"]

With ENV in Dockerfile:

ENV STREAMLIT_SERVER_ADDRESS=0.0.0.0

ENV STREAMLIT_SERVER_HEADLESS=true

ENV STREAMLIT_SERVER_PORT=8080

Full Dockerfile:

FROM python:3.11-slim

RUN mkdir -p /data

WORKDIR /app

COPY requirements.txt .

RUN pip install --no-cache-dir -r requirements.txt

COPY . .

ENV STREAMLIT_SERVER_ADDRESS=0.0.0.0

ENV STREAMLIT_SERVER_HEADLESS=true

ENV STREAMLIT_SERVER_PORT=8080

CMD ["streamlit", "run", "layout.py"]

Try CMD ["sh", "-c", "streamlit run layout.py --server.address=0.0.0.0 --server.port=${PORT:-8080}"].

Still same error with your suggested CMD:

CMD ["sh", "-c", "streamlit run layout.py

--server.address=0.0.0.0 --server.port=${PORT:-8080}"]

Error: Invalid value for '--server.port'

(env var: 'STREAMLIT_SERVER_PORT'): '$PORT'

is not a valid integer

It seems STREAMLIT_SERVER_PORT=$PORT is being injected

BEFORE our CMD runs and Streamlit reads the env var

before our CLI args can override it.

Is Railway auto-setting STREAMLIT_SERVER_PORT for

Streamlit apps? How can we clear it?

1. Delete the Lingering Variable in Railway

When you initially deployed using Nixpacks, Railway likely auto-detected Streamlit and injected STREAMLIT_SERVER_PORT=$PORT into your service's environment. Switching to a Dockerfile builder doesn't delete old variables.

1. Go to your Railway Dashboard.

2. Click on your Streamlit service.

3. Go to the Variables tab.

4. Find STREAMLIT_SERVER_PORT (and any other auto-generated STREAMLIT_ variables you didn't manually set).

5. Delete them.

2. Update Your Dockerfile

Railway dynamically assigns a port to your container via the $PORT environment variable. Now that the bad variable is gone, you can tell Streamlit to use Railway's $PORT natively in the CMD.

Here is the clean Dockerfile to use:

Dockerfile

FROM python:3.11-slim

# Create the data directory (Railway will mount the volume over this)
RUN mkdir -p /data

WORKDIR /app

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY . .

# Set static Streamlit configurations
ENV STREAMLIT_SERVER_ADDRESS=0.0.0.0
ENV STREAMLIT_SERVER_HEADLESS=true

# Launch Streamlit using Railway's dynamic $PORT
CMD ["sh", "-c", "streamlit run layout.py --server.port=$PORT"]

3. Verify the Volume Mount

Once your container actually boots without crashing from the port error, your volume mount should finally work.

• Double-check in Railway under Settings > Volumes that your persistent volume is mapped exactly to /data.

• Because you are now using a Dockerfile, the volume will be attached properly during the infrastructure boot sequence, avoiding the timing desync you experienced with Nixpacks.

Confirmed - STREAMLIT_SERVER_PORT is NOT in our variables.

Only Cloudinary vars exist. Railway must be auto-injecting it.

How do we prevent Railway from auto-setting

STREAMLIT_SERVER_PORT for Streamlit apps?

Update: Confirmed STREAMLIT_SERVER_PORT is NOT in our

service variables. Only Cloudinary vars exist.

But Railway is still injecting STREAMLIT_SERVER_PORT=$PORT

(literal string) automatically.

Even tried ${{PORT}} reference syntax - still same error.

Our Dockerfile CMD:

CMD ["/bin/sh", "-c", "streamlit run layout.py

--server.port $PORT --server.address 0.0.0.0"]

The /bin/sh -c command never seems to execute at all.

Is there a way to see ALL environment variables that

Railway injects at runtime, including auto-generated ones?

Or is there a way to completely disable Railway's

auto-detection for Streamlit?

Still same error after deleting STREAMLIT_SERVER_PORT

from variables and redeploying.

Railway must be auto-injecting STREAMLIT_SERVER_PORT=$PORT

internally for Streamlit apps even when not set in variables.

Our Dockerfile:

FROM python:3.11-slim

RUN mkdir -p /data

WORKDIR /app

COPY requirements.txt .

RUN pip install --no-cache-dir -r requirements.txt

COPY . .

ENV STREAMLIT_SERVER_ADDRESS=0.0.0.0

ENV STREAMLIT_SERVER_HEADLESS=true

CMD ["/bin/sh", "-c", "streamlit run layout.py --server.port $PORT --server.address 0.0.0.0"]

No STREAMLIT_SERVER_PORT in variables.

Still getting: '$PORT' is not a valid integer

Is Railway auto-injecting this for Streamlit detection?

Unable to Open it

Update: Resolved temporarily by reverting to Nixpacks.

The Dockerfile approach was failing because Railway was

auto-injecting STREAMLIT_SERVER_PORT=$PORT (literal string)

which Streamlit couldn't parse as an integer. Even hardcoding

STREAMLIT_SERVER_PORT=8080 in Dockerfile ENV and Railway

Variables was being overridden.

Workaround: Reverted to Nixpacks — app is now live at

app.liluboutique.com

Remaining issue: Railway Volume (/data) is not mounting

with Nixpacks. The /data directory shows exists=False

in deploy logs despite volume being attached.

Is there a way to use Nixpacks with a properly mounted

volume? Or fix the STREAMLIT_SERVER_PORT injection issue

so we can use Dockerfile builder with volume support?

Thank you for all the help!