Kubernetes config map symlinks (..data/) : is there a way to avoid them?

Question

I have noticed that when I create and mount a config map that contains some text files, the container will see those files as symlinks to ../data/myfile.txt .

For example, if my config map is named tc-configs and contains 2 xml files named stripe1.xml and stripe2.xml, if I mount this config map to /configs in my container, I will have, in my container :

bash-4.4# ls -al /configs/ total 12 drwxrwxrwx    3 root     root          4096 Jun  4 14:47 . drwxr-xr-x    1 root     root          4096 Jun  4 14:47 .. drwxr-xr-x    2 root     root          4096 Jun  4 14:47 ..2018_06_04_14_47_03.291041453 lrwxrwxrwx    1 root     root            31 Jun  4 14:47 ..data -> ..2018_06_04_14_47_03.291041453 lrwxrwxrwx    1 root     root            18 Jun  4 14:47 stripe1.xml -> ..data/stripe1.xml lrwxrwxrwx    1 root     root            18 Jun  4 14:47 stripe2.xml -> ..data/stripe2.xml 

I guess Kubernetes requires those symlinks and ../data and ..timestamp/ folders, but I know some applications that can fail to startup if they see non expected files or folders

Is there a way to tell Kubernetes not to generate all those symlinks and directly mount the files ?

Answer 1

I think this solution is satisfactory : specifying exact file path in mountPath, will get rid of the symlinks to ..data and ..2018_06_04_19_31_41.860238952

So if I apply such a manifest :

apiVersion: v1 kind: Pod metadata:   name: my-lamp-site spec:     containers:     - name: php       image: php:7.0-apache       volumeMounts:       - mountPath: /var/www/html/users.xml         name: site-data         subPath: users.xml     volumes:     - name: site-data       configMap:         name: users  ---  apiVersion: v1 kind: ConfigMap metadata:   name: users data:   users.xml: |       <?xml version="1.0" encoding="UTF-8" standalone="yes"?>       <users>       </users> 

Apparently, I'm making use of subpath explicitly, and they're not part of the "auto update magic" from ConfigMaps, I won't see any more symlinks :

$ kubectl exec  my-lamp-site -c php -- ls -al /var/www/html total 12 drwxr-xr-x 1 www-data www-data 4096 Jun  4 19:18 . drwxr-xr-x 1 root     root     4096 Jun  4 17:58 .. -rw-r--r-- 1 root     root       73 Jun  4 19:18 users.xml 

Be careful to not forget subPath, otherwise users.xml will be a directory !

Back to my initial manifest :

spec:     containers:     - name: php       image: php:7.0-apache       volumeMounts:       - mountPath: /var/www/html         name: site-data     volumes:     - name: site-data       configMap:         name: users 

I'll see those symlinks coming back :

$ kubectl exec  my-lamp-site -c php -- ls -al /var/www/html total 12 drwxrwxrwx 3 root root 4096 Jun  4 19:31 . drwxr-xr-x 3 root root 4096 Jun  4 17:58 .. drwxr-xr-x 2 root root 4096 Jun  4 19:31 ..2018_06_04_19_31_41.860238952 lrwxrwxrwx 1 root root   31 Jun  4 19:31 ..data -> ..2018_06_04_19_31_41.860238952 lrwxrwxrwx 1 root root   16 Jun  4 19:31 users.xml -> ..data/users.xml 

Many thanks to psycotica0 on K8s Canada slack for putting me on the right track with subpath (they are quickly mentioned in configmap documentation)