Reading a container's /proc/loadavg, but on the host itself

LXCFS
1

System information
Ubuntu 22.04.3
Linux kernel 6.4.6
LXC 5.0.0 (from Ubuntu’s universe repo)
LXCFS service configured with --enable-loadavg, and working perfectly

Question

I would like to read a container’s /proc/loadavg, but without needing to enter on it to do so.

Is there is any file on the host where I could read this specific virtualized mountpoint without entering in the container itself? Or an lxc command?

I already did a research on many directories, including /sys/fs/cgroup/, /var/lib/lxc, /var/lib/lxcfs, to no avail.

The current challenges:

  • lxc-top only provides the current CPU usage, not the three averages (of 1 minute, 5 and 15), like /proc/loadavg
  • entering the container to read the file can be susceptible to slowdowns if the container is performing heavy tasks
2

The solution is to read the “live” filesystem from the container through /proc/<container-pid>/root/

For example, to read /proc/loadavg from a container named test-container:

1. Get the container current PID

$ lxc-info -n test-container

Name:           test-container
State:          RUNNING
PID:            10835
IP:             10.0.3.64
Link:           vethOoD3AW
 TX bytes:      1.89 KiB
 RX bytes:      2.14 KiB
 Total bytes:   4.03 KiB

2. Read the relative path, starting with the prefix /proc/<container-pid>/root/:

$ cat /proc/10835/root/proc/loadavg

0.00 0.00 0.00 0/1 11202