a month ago
Hi — two questions about a Next.js + Postgres project on Railway. Project: gco-hub, two services on the same repo (one tied to develop for staging, one tied to main for production). The
setup uses Dockerfile builds and a predeploy command for DB migrations + seeding.
Question 1 — preDeployCommand parsing of &&
My initial railway.json had:
"deploy": {
"preDeployCommand": ["npm run db:migrate && npm run db:seed"]
}
A single array element containing two npm scripts chained with &&.
bserved behavior on every staging deploy with this config:
▎ - npm run db:migrate ran successfully — log shows Running migrations against postgres://***... followed by Migrations complete.
▎ - The && chain did NOT continue to npm run db:seed. No seed output appeared.
▎ - Deployment was reported as successful, container started normally.
▎ - Manually running railway run npm run db:seed against the same environment works perfectly and produces the expected output.
▎
▎ Question: when preDeployCommand is an array of strings, are array elements run via direct exec (so shell operators like &&, |, > are treated as literal arguments), or via a shell? Your
▎ schema (backboard.railway.app/railway.schema.json) shows "items":{"type":"string"},"maxItems":1 for the array form, which suggests array elements aren't intended for chaining — but isn't
▎ documented anywhere I could find.
▎
▎ I've since switched to the string form:"preDeployCommand": "npm run db:migrate && npm run db:seed"
▎ Could you confirm:
▎ 1. Is the string form shell-evaluated and the array form exec'd?
▎ 2. What's the canonical pattern for chaining multiple commands in a predeploy?
▎ 3. Is there a recommended way to verify the predeploy command's full stdout in the dashboard (the deploy log view in our case seems to truncate or omit the post-Migrations complete.
▎ lines)?
Pinned Solution
a month ago
Hello seif57,
you're using a dockerfile andd with dockerfile builds, && is shell-specific syntax and won't work unless you explicitly wrap the command in a shell doesn't matter if you use the array or string form without the shell wrapper it won't chain
the fix is:
"preDeployCommand": "/bin/sh -c "npm run db:migrate && npm run db:seed""
Hope this help you :)
4 Replies
a month ago
The preDeployCommand array form uses exec form (like Dockerfile ENTRYPOINT), so shell operators like && are not interpreted - they're passed as literal arguments to the process. The string form is shell-evaluated, so "npm run db:migrate && npm run db:seed" as a plain string is the correct way to chain commands. The schema's maxItems: 1 on the array form confirms it's designed for a single command, not chaining. Pre-deploy command output appears in the deploy logs under the "pre-deploy" phase in the dashboard.
Status changed to Awaiting User Response Railway • about 1 month ago
a month ago
I did that and reseeding didn't work
Status changed to Awaiting Railway Response Railway • about 1 month ago
Status changed to Open Railway • about 1 month ago
a month ago
Hello seif57,
you're using a dockerfile andd with dockerfile builds, && is shell-specific syntax and won't work unless you explicitly wrap the command in a shell doesn't matter if you use the array or string form without the shell wrapper it won't chain
the fix is:
"preDeployCommand": "/bin/sh -c "npm run db:migrate && npm run db:seed""
Hope this help you :)
domehane
Hello **seif57,** you're using a dockerfile andd with dockerfile builds, && is shell-specific syntax and won't work unless you explicitly wrap the command in a shell doesn't matter if you use the array or string form without the shell wrapper it won't chain the fix is: "preDeployCommand": "/bin/sh -c "npm run db:migrate && npm run db:seed"" Hope this help you :)
a month ago
or if you want to avoid escaping quotes, put both commands in a shell script in your repo and do:
"preDeployCommand": "/bin/sh ./scripts/predeploy.sh"
Status changed to Solved 0x5b62656e5d • 24 days ago