when set  runAsUser/runAsGroup /fsGroup=9999 at securityContext, it takes effect. while two unexpected observation: 

1. why no group id found at '/etc/groups' ?
   bash-5.2$ cat /etc/group | grep 9999
   bash-5.2$

2. why it's different output from below command ?
bash-5.2$ id
uid=9999(9999) gid=9999 groups=9999
bash-5.2$ id 9999
uid=9999(9999) gid=0(root) groups=0(root)

  set runAsGroup explicitly and check if group id exists in /etc/group inside container. 


Create POD with below securitycontext
securityContext:
runAsUser: 64892
runAsGroup: 6263
fsGroup: 123Inside container no group id is created at /etc/group
bash-5.2$ id
uid=64892(64892) gid=6263 groups=6263,123
bash-5.2$ id 64892
uid=64892(64892) gid=0(root) groups=0(root)
bash-5.2$ cat /etc/passwd | grep 64892
64892:x:64892:0:64892 user:/:/sbin/nologin
bash-5.2$ cat /etc/group | grep 6263
bash-5.2$    

 if group id is appointed by runAsGroup, this group id should exist at /etc/group inside container.