inside a container, things look different2`

Illustration of a smiling stick figure with curly hair.

Person: I only see 4 processes in ps aux, that’s weird…

why things look different: namespaces

Illustration of a container, represented by a box with a smiley face

Container: I’m in a different PID namespace so ps aux shows different processes!

every process has 7 namespaces

$ lsns -p 273
NS TYPE
4026531835 cgroup
4026531836 pid
4026531837 user
4026531838 uts
4026531839 ipc
4026531840 mnt
4026532009 net

-p is the PID
4026532009 is the namespace ID

you can also see a process’s namespace with: $ ls -1 /proc/273/ns

there’s a default (“host” namespace)

Person: “outside a container” just means “using the default namespace”

processes can have any combination

Container: I’m using the host network namespace but my own mount container namespace!