When Docker Containers Keep Restarting — Causes and Fixes by Exit Code

Primary sources

Decision table: Exit codes, causes, and fixes

Exit code	Meaning	Typical cause	Fix
`0`	Normal exit	The container finished its work (intentional exit)	No action needed
`1`	Application error	Application runtime error	Review logs; check env vars and ports (`docker logs`, `docker inspect`)
`137`	SIGKILL	OOM Killer or `docker kill`	Check memory usage and raise the limit (`docker stats`, `docker run -m 512m`, `docker-compose.yml mem_limit: 512m`)
`139`	Segfault	Application memory corruption	Debug the code and improve memory handling
`143`	SIGTERM	Clean shutdown after `docker stop`	No action needed

Step 1 — Check status and exit code

Bash

# All container statuses (including stopped)
docker ps -a

# Example output
# CONTAINER ID  IMAGE    STATUS                     NAMES
# abc123        myapp    Restarting (1) 5s ago      myapp
# def456        nginx    Exited (137) 2 minutes ago nginx
#                        ↑ exit code

Step 2 — Check container logs

Bash

# Last 100 lines of logs
docker logs --tail 100 container-name

# Follow logs in real time (useful while restarts are looping)
docker logs -f container-name

# Include timestamps
docker logs -t --tail 50 container-name

# Works for stopped containers too
docker logs container-id

Exit code 1 — Application crash

Check the logs for error messages.

Bash

docker logs container-name 2>&1 | tail -30

Common causes:

Missing environment variable: Error: DATABASE_URL is not defined
Port conflict: Error: listen EADDRINUSE :::3000
Missing file/config: No such file or directory

Bash

# Check environment variables
docker inspect container-name | grep -A 20 '"Env"'

# Inspect inside a one-off container
docker run --rm -it --env-file .env image-name /bin/sh

Exit code 137 — OOM kill

Bash

# Check whether it was OOM-killed
docker inspect container-name | grep -i oom
# "OOMKilled": true means OOM

# Check memory usage
docker stats --no-stream container-name

Bash

# Increase the memory limit (docker run)
docker run -m 512m image-name

# docker-compose.yml
# services:
#   myapp:
#     mem_limit: 512m

Check and change the restart policy

Bash

# Check the current restart policy
docker inspect container-name | grep -A 3 'RestartPolicy'

Policy	Behavior
`no`	Do not restart (default)
`always`	Always restart (regardless of exit code)
`on-failure`	Restart only on non-zero exit
`unless-stopped`	Always restart until manually stopped

Bash

# If restart loops are the problem, switch the policy to on-failure
docker update --restart=on-failure:5 container-name
# Stop after 5 attempts

# Stop completely
docker update --restart=no container-name
docker stop container-name

Debugging — start the container manually

Bash

# Ignore the entrypoint and drop into a shell (inspect the cause directly)
docker run --rm -it --entrypoint /bin/sh image-name

# Enter a shell with the existing container's env
docker run --rm -it   $(docker inspect container-name --format '{{range .Config.Env}}-e {{.}} {{end}}')   --entrypoint /bin/sh   image-name

FAQ

Q. docker ps keeps showing Restarting. Where should I start? A. Start with docker logs <container> to see the output just before exit. Then get the exit code with docker inspect <container> --format '{{.State.ExitCode}}'. 137 = OOM (out of memory), 1 or 2 = application exception, 126 or 127 = missing executable or a permission problem. If the restart policy is always, the container will loop forever every time the app dies, so switch to --restart=no first so you can capture logs.

#Docker#Restarting#Exited#exit code#Troubleshooting#restart policy#container

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