debug in openshift

Debug-In-OpenShift/README.md

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+# How to debug issues in OpenShift
+
+## Context
+
+Lets say that you deployed an application in OpenShift and the application is not working.
+You would like to debug but the application does not embed any troubleshooting tool (for instance, an Alpine Linux or a scratch image)
+
+Two approaches are possible:
+
+- download statically compiled tools in the `/tmp` of the container
+- add a side-car container with the required tools
+
+## Static tools
+
+You could download one of the [static tools available there](https://github.com/andrew-d/static-binaries)
+in `/tmp` and run it from there.
+
+## Sidecar container
+
+For instance, if you need to troubleshoot network issues:
+
+**Deploy our boggus application**
+
+```sh
+oc new-app --name boggus alpine:latest
+oc patch dc boggus --type=json -p '[{"op": "add", "path": "/spec/template/spec/containers/0/command", "value": ["/bin/sh", "-c", "while :; do sleep 1; done" ]}]'
+```
+
+**Add a sidecar container that has the tools to debug network issues**
+
+```sh
+oc patch dc boggus --type=json -p '[{"op": "add", "path": "/spec/template/spec/containers/1", "value": { "image": "szalek/pentest-tools", "name": "debug", "command": [ "/bin/sh", "-c", "while :; do sleep 1; done" ]} }]'
+```
+
+**Enter the sidecar container**
+```sh
+oc rsh -c debug $(oc get pods -l app=boggus -o name|tail -n 1)
+```
+
+For strace, it is a bit more complicated since you will have access to the host PID namespace.
+
+**Give privileged rights to the default service account**
+```sh
+oc adm policy add-scc-to-user privileged -z default
+```
+
+**Add a sidecar container that has strace**
+
+```sh
+oc patch dc boggus --type=json -p '[{"op": "add", "path": "/spec/template/spec/containers/1", "value": { "image": "benhall/strace-ubuntu", "name": "debug", "command": [ "/bin/sh", "-c", "while :; do sleep 1; done" ], "securityContext": { "privileged": true } } }, {"op": "add", "path": "/spec/template/spec/hostPID", "value": true } ]'
+```
+
+**Enter the sidecar container**
+
+```sh
+oc rsh -c debug $(oc get pods -l app=boggus -o name|tail -n 1)
+```
+
+**In the container, try:**
+
+```sh
+ps ax
+```
+
+**and then:**
+```sh
+strace -ff -p <pid>
+```