find container against pid !!

[shahzaib]

Hi,

We recently moved to proxmox-4.2 which is under high load & we are seeing some processes causing high usage. If we try to find the container associated to that process PID using vzpid it gives "0" CTID in the output. In older versions, it used to provide accurate CTID but not now. Here is the output of vzpid :


root@vnode:~# vzpid 19662
Pid CTID Name
19662 0 bundle

Is there any changes in newer versions ? Also i can see pct is recommend instead of vz commands now.

 

[fabian]

Hi,

We recently moved to proxmox-4.2 which is under high load & we are seeing some processes causing high usage. If we try to find the container associated to that process PID using vzpid it gives "0" CTID in the output. In older versions, it used to provide accurate CTID but not now. Here is the output of vzpid :


root@vnode:~# vzpid 19662
Pid CTID Name
19662 0 bundle

Is there any changes in newer versions ? Also i can see pct is recommend instead of vz commands now.

not recommended - the openvz commands simply don't work with LXC containers and vice versa.

an easy way to find out in which LXC container a process runs is by looking at the contents of /proc/PID/cgroup

 

[shahzaib]

Thanks for useful tip.

 

[t.lamprecht]

Edit: did not saw fabians reply, had the response already written but forgot to send

Hi,
yes a lot changed from PVE 3.x to PVE 4.x. The in its old form discontinued OpenVZ project was replaced with LXC (LinuX Container), so the old tools from openvz (vzctl, vzpid, but NOT vzdump) are not able to interact with LXC. So using our container tool (pct) is recommended.

pct has currently no support for mapping PID to VMID, but under linux such information is easily available through the /proc filesystem.
You could get the info with:

grep -oP "(?<=pids:/lxc/)\d+" "/proc/PID/cgroup"

just replace PID with the respective integer.

Or as a more advanced shell script with error checks and which accepts the PID as parameter:

#!/bin/sh

if [ ! -e "/proc/$1/cgroup" ]; then
   echo "no process with PID '$1' found!"
   exit 1
fi

grep -oP "(?<=pids:/lxc/)\d+" "/proc/$1/cgroup" || (echo "process with PID '$1' does not belong to an PVE CT"; exit 1)

(link to gist)

Save this on the node, I named it pid_to_vmid, make it executable with

chmod +x pid_to_vmid

Now you can call it with

./pid_to_vmid 12345

 

[Morphushka]

Maybe it helps, but now there is no more "pids" literals in "/proc/$1/cgroup" (or I miss something?), so I change regex a little bit:

(?<=:\/lxc\/)\d+

and script works again.

 

[t.lamprecht]

Ah yes, my script was for cgroupv1 not v2, which is the new default since Proxmox VE 7.0 from 2021 and uses a bit of a different format on some parts