check_mk agent install on CentOS 7 by systemd

Here is the steps I install check_mk agent on CentOS 7 by systemd only without xinit.

first scp the rpm package to CentOS server, then install it:
rpm -ivh check-mk-agent-1.2.8p18-1.noarch.rpm

Open the port 6556:
firewall-cmd --permanent --add-port=6556/tcp
firewall-cmd --reload

Double check the status:
firewall-cmd --list-ports
firewall-cmd --list-services

Restart to make sure the check_mk_agent start on boot.

Hope this helps.

check_mk hang on start with mkeventd

1. Starting mkeventd (builtin: snmptrap)...Cannot bind UDP socket for snmptrap to port: Permission denied

2. It just hang and waiting forever on Starting mkeventd (builtin: snmptrap)...

I found a lot files in /opt/omd/sites/(sitename)/var/mkeventd/status.

Have to manually delete the status and history files to start the mkeventd.

HHVM 3.18.0 crash on Ubuntu 16.04 with Nginx

Just try to bring up an new HHVM host on Ubuntu 16.04 with Nginx.

But HHVM keep crush error in /var/log/hhvm/error.log
It created error log in /tmp

Here is a example:

Run ls -alt /var/run/hhvm
Since upgrading to 3.18, hhvm is unable to open hhvm.hhbc as it is created as root instead of www-data.

For now the workaround is to add the following to your configuration: /etc/hhvm/server.ini

Restart the HHVM service.

And it works.

Hope HHVM team can fix it in the next release.


check_mk How to fix:Disk Mount Changes showing error

Sometimes few hosts in my check_mk build showing Disk Mount error.

For example:
“Mount options of / – – – – CRIT – mount options are
> > > acl,barrier=0,data=ordered,errors=remount-ro,noatime,rw,user_xattr,
> > > expected are barrier=0,data=ordered,errors=remount-ro,noatime,rw”

But there isn’t any changes recently.

I just su to my site and refresh the hosts manually:

Restart the check_mk, that will make the nonsense error goes away.

check_mk ALL Hoststate down, check_icmp: Failed to obtain ICMP socket: Operation not permitted

I upgrade my production check_mk site to the latest 1.2.8p14.

Suddenly all Hosts shows down.

Restart the site, everything back to normal.

This happens after I update check_mk to the latest stable Version: 1.2.8p14
Hope it helps.

check_mk outdate error message: Disk Mount Changes network interface speed wrong

A lot time I got these kind of wrong error message like:

Disk Mount changes but missing mount option.
Or Network interface 1 is 10GB but should be 1 GB.

Which is just the check_mk output outdate issue.

Here is what I do to refresh the $host in check_mk:

Sometimes I have to restart omd site, but it should be enough to give you back the correct output.

mongodb 3.2 logrotate

Installed latest mongodb 3.2 on Debian 8 Jessie.

It does not came with logrotate configure file.

Here is mine:

Add reopen in /etc/mongod.conf

Using -SIGUSR1 to rotate the log file:


check_mk agent start by systemd Debian Jessie

I use check_mk everywhere.

For the old school, on Debian system you need install xinetd to start it.
But since we have systemd in Debian 8 Jessie, it will be much cleaner to do systemd way.

Here is how I do it:

  1. Fist if you previous using xinetd, stop and remove it.
  2. And run autoremove to cleanup

  3. Then check your check_mk agent version:
  4. Next enable the check_mk in systemd autostart.
  5. Finally start the service.
  6. A special notice, because the systemd not allow the IP rules like xinetd does.
    You will have to update your firewall to restrict other accessing.

    Hope this helps, please let me know if you have any questions.

replace with sed in directory and sub directories

  1. # goto the folder
  2. # verify how many strings exist.
  3. # replace
  4. # double check the result.

How to put Cache into RamDisk

I recently upgrade memory on working PC.
Want put cache into Ramdisk and save some life of SSD.

The Ramdisk Application I am using is: SoftPerfect RAM Disk.

Here are my changes:

    1. Put Google Chrome Cache into RamDisk:

    1. Put Firefox Cache into RamDisk:

    1. Put VLC Media Player ART into RamDisk:

    1. Put Microsoft Edge Cache into RamDisk:

I accident delete the Edge profile folder.

Do not delete the top folder!

Recovery from PowerShell:

    1. Redirect the Temp folder even I change the Windows TEMP Path:

    1. Thumbcache folder can’t be redirect!