Why Did My ROS 2 Docker Container Disappear After a Month?

Check whether Docker’s data directory is on an external drive that failed to mount. On a Raspberry Pi, Docker may appear empty if `/var/lib/docker` is located on a drive that is currently unavailable. These commands can help verify the mounts and filesystem: `lsblk -f`, `blkid`, `df -h -T`, `findmnt`, and `cat /etc/fstab`. If the drive is mounted again, the container may become visible without being restored.

First check whether the image and container still exist with `docker images` and `docker ps -a`. If the images are present but the container is missing, the most likely causes are that it was started with `--rm`, which automatically deletes it when it stops, or that a cleanup command such as `docker system prune` removed stopped containers. A reboot during that time could have triggered the issue if `--rm` was used. For the future, keep the setup in a Docker Compose file so the container can be recreated easily.

First determine whether the container data is actually gone or whether Docker is using a different data root. You can inspect `/var/lib/docker/containers/`; directories with long hexadecimal names indicate that container data may still be there. If the directory is empty, possible causes include a scheduled `docker system prune`, starting the container with `--rm`, or filesystem corruption on the Pi’s SD card. For corruption, check `dmesg -T | grep -iE "ext4|i/o error"` and inspect `lost+found`. Also, `docker events` is not a long-term audit log—it only reports events while it is running—so Docker itself may not have a record of what happened. A Compose file stored with the project will make recovery much easier next time.