Optimizing Checkmk Performance: When to Disable the Agent Receiver

In Checkmk version 2.1 and newer, the Agent Receiver (listening on Port 8000) is a core process responsible for managing the Agent Controller. It handles the secure registration, TLS encryption, and the "Push" mode functionality of modern agents.

However, if you are running a lean environment or monitoring older infrastructure, you might find that you don't need these modern overheads.

The Case for "Legacy Mode" While the Agent Receiver is a powerful tool for security, it does consume system resources (CPU and Memory). If you are looking to squeeze every bit of performance out of your Checkmk server, you can revert to Legacy Pull Mode.

In this mode, the server connects directly to the monitored host via Port 6556 to retrieve plain-text data, bypassing the need for the Receiver entirely.

Warning: Disabling the Agent Receiver means you will lose TLS encryption for your monitoring data and the ability to use "Push" agents. Ensure your network is trusted before making this change.

To switch to Legacy Mode and free up system resources, follow these steps to update your site configuration:

1. Check the setting of Agent Receiver before make change.

omd config show | grep AGENT_RECEIVER

2. Stop your Checkmk site.

omd stop

3. Change the Receiver setting to off.

omd config set AGENT_RECEIVER off

4. Restart site to apply the changes.

omd start

5. Verification.

omd status

Prevent creation of .vmem files in VMware workstation (Windows)

Learned how to Disable VMWare Workstation VMEM file on all Virtusl Machines on Windows 11.

Stop all running Virtual Machines.

Close VMware workstation.

Edit "C:\ProgramData\VMware\VMware Workstation\settings.ini" as Administrator>

Add 5 lines :

mainMem.useNamedFile = "FALSE"
prefvmx.minVmMemPct = "100"
MemTrimRate = "0"
sched.mem.pshare.enable = "FALSE"
prefvmx.useRecommendedLockedMemSize = "TRUE"

Disable Kernel modules in Alpine Linux Cloud image for Oracle Cloud

Download Alpine Linux Cloud Image from: https://www.alpinelinux.org/cloud/

Upload the image to OCI and create an instance from it.

I disabled some Kernel modules for security and saving memory.

Remove old drivers from: /etc/mkinitfs/mkinitfs.conf
From:

features="ata base ide scsi usb virtio ext4 nvme"

To:

features="base scsi virtio ext4"

Add 'blacklist drm' to /etc/modprobe.d/blacklist.conf

echo 'blacklist drm' >> /etc/modprobe.d/blacklist.conf
mkinitfs -c /etc/mkinitfs/mkinitfs.conf -b / 
reboot

The grub modprobe.blacklist=drm, does not work either.

updating /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash modprobe.blacklist=drm"

I will try [cloud-init] Bootstrap image next time.

Reference:
https://dev.alpinelinux.org/~clandmeter/other/forum.alpinelinux.org/forum/kernel-and-hardware/blacklist-drivers-builtin-kernel.html
https://wiki.alpinelinux.org/wiki/Initramfs_init
https://wiki.alpinelinux.org/wiki/Xen_PCI_Passthrough

reduce checkmk OK -> CRITICAL -> OK on host or service by maximum number of check attempts settings

Checkmk may send out numerous alerts for external hosts or services. It can be overly sensitive at times.

To reduce the frequency of Checkmk sending alerts that switch from OK to CRITICAL and then back to OK within a minute, consider adjusting the maximum number of check attempts.

maximum number of check attempts for host → 3
maximum number of check attempts for services → bigger then 3 normally 4 or 5

Direct link for the Zoom Web App client

The zoom desktop client is a heavy app under Linux.

If you want someone to join your meeting without installing the Zoom app, you can send them a join link for the Web Client.
You can use our Web Client as the join_url without leaving the website by replacing /j/ with /wc/.

https://zoom.us/wc/{meetingID}/join

If you like to join with having the user type in their names you can base64 their names at the end of the url.

https://zoom.us/wc/{meetingID}/join?prefer=1&un={base64-firstname-lastname}

Make sure that you’ve also enabled the Join From Your Browser link

Reference: Launch Zoom Web App client without direct.