[SOLVED] RAM Usage in Pure LXC Container

Software & Web Applications
1

By “Pure LXC,” I meant LXC that uses the “lxc-*” commands and not “lxc *” as used by LXD. LXC and LXD gets used interchangeable and if I search in Google or Kagi for anything related to LXC, I get search results that talk about LXD, even though I never mentioned LXD in the list of keywords. With that out of the way…

Here is the basic configuration for my LXC container:

root@vmserver:~# cat /data/vm/lxc/vyos/config
# Template used to create this container: /usr/share/lxc/templates/lxc-download
# Parameters passed to the template:
# Template script checksum (SHA-1): 47a9fc1ce184c958ecafc88dfd5f21c06f728288
# For additional config options, please look at lxc.container.conf(5)

# Uncomment the following line to support nesting containers:
#lxc.include = /usr/share/lxc/config/nesting.conf
# (Be aware this has security implications)


# Distribution configuration
lxc.include = /usr/share/lxc/config/common.conf
lxc.arch = linux64

# Container specific configuration
lxc.rootfs.path = dir:/var/lib/lxc/vyos/rootfs
lxc.uts.name = vyos

lxc.start.auto = 1

lxc.autodev = 1
lxc.hook.autodev = sh -c "mknod -m 0666 ${LXC_ROOTFS_MOUNT}/dev/fuse c 10 229"

# Network configuration
lxc.net.0.type = veth
lxc.net.0.link = brVMNet
lxc.net.0.flags = up
lxc.net.0.hwaddr = 02:16:3e:08:75:40

lxc.net.1.type = veth
lxc.net.1.link = brVLabNet1
lxc.net.1.flags = up
lxc.net.1.hwaddr = 02:09:3f:04:35:70

Once I execute lxc-attach vyos and run the free -m command, I get this:

vyos@vyos:~$ free -m
               total        used        free      shared  buff/cache   available
Mem:           46068        4222         762           8       41659       41846
Swap:           8191           0        8191

Note that the used column shows the entire host memory usage and not the container memory usage. Is there a way to show only the memory usage for the container?

2

Does “ lxc-info -n vyos” work?

3

Output:

Name:           vyos
State:          RUNNING
PID:            1626873
IP:             172.20.100.1
IP:             172.20.30.64
Link:           veths4ZDbn
 TX bytes:      916 bytes
 RX bytes:      451.27 KiB
 Total bytes:   452.16 KiB
Link:           vethfkuYyg
 TX bytes:      916 bytes
 RX bytes:      2.35 KiB
 Total bytes:   3.24 KiB

Only IP addresses and network stats.

4

https://man7.org/linux/man-pages/man1/lxc-info.1.html

5

I looked at the list of switches but I did not look at the man page.

performance reasons the kernel does not account kernel memory use unless a kernel memory limit is set.

So it looks like I need to set a memory limit before I can see how much my container uses. Well, guess I’ll have to do a lot more searching on my own.

Thanks.

6

I got it! lxcfs is needed to emulate a couple of files in /proc which will allow me to see available memory!

I installed lxcfs, started the service (I’m in Fedora Server), and in my container, what I get is this:

root@vmserver:~# lxc-attach vyos
root@vyos:~# free -m
               total        used        free      shared  buff/cache   available
Mem:           46068         140       45925           0           1       45927
Swap:              0           0           0

So now I only see how much memory that VyOS is using and that is awesome! :grinning:

With that, my problem is solved!

Source:

1 Like
7

Out of curiosity, does the cgroup top command work with lxc? On the host run; systemd-cgtop

It’s been years since I used lxc and I just can’t remember if this works. Might be another way to find this info.

8

systemd-cgtop is for showing slices and services in real-time. I had to stop the “animation” by pressing Ctrl+C because it’s preventing me from reading what’s going one due to my visual impairment.

Anyway, the problem is now solved thanks to installing and starting lxcfs.

9

You can run it once and specify the machine. For my unifi container I run; systemd-cgtop -1 -M wifi

If you just want to quickly check the container resources usage this requires far less work. But to each his own, glad you solved this problem.