2019-12-09 • OPENSHIFT , DOCKER

Docker Core Dumps

Docker Core Dumps

Get the container id (CID) of the pod to be checked. From the node running the pod. You will need to be able to identify your container ID.
```
# docker ps
# CID=xxx
```
Check if docker is logging
```
# docker logs <CID>
```
Check node’s journal
```
# journalctl CONTAINER_ID=<CID>
```

Grab lsof and gcore for each process: dockerd-current, docker-containerd-current, and docker-containerd-shim-current. This will show us open files from each process as well as provide a core dump of the running process.

# lsof -p `pidof dockerd-current` > dockerd-lsof.txt
# gcore -o containerd `pidof docker-containerd-current`
# bzip2 dockerd.`pidof dockerd-current`

# lsof -p `pidof docker-containerd-current` > containerd-lsof.txt
# gcore -o containerd `pidof docker-containerd-current`
# bzip2 containerd.`pidof docker-containerd-current`

# lsof -p `pidof docker-containerd-shim-current for <CID>` > shim-lsof.txt
# gcore -o shim `pidof docker-containerd-shim-current for <CID>`
# bzip2 shim.`pidof docker-containerd-shim-current for <CID>`

Also useful:

Check if docker is logging
```
# docker logs <CID>
```
Check node’s journal
```
# journalctl CONTAINER_ID=<CID>
```
Show all CIDs being logged to this nodes journal.
NOTE: should be ran exactly as is, do not replace CONTAINER_ID with an actual CID or you’ll get an error
```
# journalctl -F CONTAINER_ID
```