New laptop? Check your hosts. /etc/hosts

I’ve just run into a weird problem where RabbitMQ server was running EXTREMELY slow on my laptop for no apparent reason.

After trying a bunch of things and googlig for a while I’ve found out that possible reason for that might be slow host resolution. But everything was running on a localhost!

I’ve checked my /etc/hosts and found out… Well, when I’ve upgraded my MacBook Pro laptop I’ve imported all stuff from previous one (using Apple’s migration assistant), but also did change the new laptop’s network name to avoid conflicts with the old laptop being on the same network. But I did not update /etc/hosts accordingly – it only had 127.0.0.1 associated with the old network name.

Apparently, this is a big deal for RabbitMQ. I’ve been running it like that for more than a month and had no issues with any software whatsoever so far – but RabbitMQ (or possibly the underlying Erlang VM) was doing some special name resolution using my computer network name apparently, and that just didn’t work. Causing it not to report any errors though, but just run EXTREMELY (I mean it!) slow.

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MacOS Security&Privacy Allow button vs FortiClient

In order to install some of the software into macOS one has to go to Security & Privacy section of macOS preferences and click “Allow” button to allow that software to run as an OS kernel extension (or something like that).

Problem is, sometimes clicking the “Allow” button simply does nothing. Nothing at all. And there is no error message to figure out what’s the problem and what is happening.

One thing to find out the root cause of the problem though is to open Console.app that comes with macOS (inside /Applications/Utilities by default) and look there for log messages produced when clicking that “Allow” button.

In my case, as it was the case for many others, the message was roughly this:
“Dropping mouse down event because sender’s PID () isn’t 0 or self ()”.
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Retro-gaming: ZX Spectrum + X-Box 360 controller on a macOS

For those who remember and love the good old ZX Spectrum – here’s a retro-gaming lifehack to have some fun experience playing ZX Spectrum games using X-Box controller on a Mac.

Some ZX Spectrum games allow one do redefine keys in order to play them. Others support standard key mappings like QAOP+Space or QAOP+M, and some also support standard joystick configurations like Kempston joystick, which essentially uses number keys 12345 and 67890 for left/right/up/down/fire on 2 joysticks – very simple and effective scheme, that also seamlessly works with games that allow redefining keys but don’t have special joystick support.

In any of those cases X-Box 360 controller can be used on macOS – by using macOS port of Fuse ZX Spectrum emulator, that supports it out of the box. A macOS driver is also needed for X-Box controller to work with Mac, but such a thing is available too (also there is an older one from TattieBogle).
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Building kube-state-metrics from source

Today I had to build kube-state-metrics Kubernetes extra metrics exporter for Prometheus monitoring system. I wanted to build it for specific Linux (kernel) version (in my case it was Alpine Linux 3.4), and I also wanted to build a specific version of kube-state-metrics – latest stable, which is 1.3.1 currently.

I didn’t want to get latest version from master as I was not sure about it’s stability and I would have hard time re-creating the build since master would move on over time, so simply making “go get” wasn’t an option.

The process turned out to be a bit tricky – I wanted to use docker to have proper version of Go lang for Alpine Linux 3.4 while I’m on a macOS myself, but the makefile of kube-state-metrics also uses docker (for whatever silly reason that is), so I needed to build it using go build.

As it turned out, I had to do two things – install Go into Alpine 3.4 (which took some copypasting from https://github.com/docker-library/golang where they have Dockerfile for Alpine 3.7 – contents of which I used) and then get the paths right for GOPATH in order to build kube-state-metrics.

Here’s the resulting Dockerfile: Continue reading

OS X (macOS) Migration Assistant disk space bug

Hi all,

Have you ever encountered an issue with OS X (AKA macOS) Migration Assistant being stuck on restart and/or starting up screen? I know I have, and I know other people have too.

IMG_6818.JPG

If you don’t even know what Migration Assistant is, chances are you’ve used it anyway – because it’s run as an option on macOS installation – the one where you choose to import files from another drive/mac/etc. FYI.

The solution to the issue turned out to be rather simple in my case, but figuring it out took a couple of retries which all took several hours, so in total I’ve spent a few days (well, evenings) resolving the issue – and with this post I hope I can spare some people from repeating my fate.

Long story short, the issue was caused by a lack of disk space. Basically, if you choose not to import some files/folders in order to fit your data onto the target drive – Migration Assistant ignores that choice and tries to import everything. And when it runs out of disk space – it does not show any error or anything like that. Instead, import stops just as if all files were copied, installation proceeds to restart step (in case you’ve been doing it during macOS install like I did) – which gets stuck BTW. And on boot (by force reboot in my case) it was stuck on “Starting up” step. All because of lack of disk space.

The fix for me was to offload a particularly big folder to an external HDD, and then do the import.

That’s about it. Hope this helps.

RAM disk on OS X High Sierra

Here’s a code for creating RAM disk that works for me under OS X High Sierra.
One can change FS from HFS+ to something else (say, APSE, or case-sensitive/journaled FSs), but for me HFS+ is the one I want.

ramdiskSizeMB=$(osascript -e 'return text returned of (display dialog "RAM disk size in MB" default answer "1024")')
echo Creating RAM disk of size $ramdiskSizeMB MB
hdidOutput=$(hdid -nomount ram://$((2048*ramdiskSizeMB)) | cut -d ' ' -f 1) && diskutil erasedisk "HFS+" ramdisk $hdidOutput

To free the RAM one can simply unmount it in finder or DiskUtility.

P.S. Updated version with FS type selection:

#!/bin/bash

choiceScript='return choose from list {';
while read -r fsType 
do
  choiceScript="${choiceScript}\"$fsType\","
done <<EOT
$(diskutil listFilesystems -plist | grep Personality -A 1 | grep -F "<string>" | grep -E -o ">[^<]+<" | grep -o -E "[^><]+" | sort)
EOT
choiceScript="${choiceScript}\"\"} with prompt \"Choose filesystem type\" "

ramdiskSizeMB=$(osascript -e 'return text returned of (display dialog "RAM disk size in MB" default answer "1024")')
if [ "$ramdiskSizeMB" != "" ]
then
  fsType=$(osascript -e "$choiceScript")

  if [ "$fsType" != "false" ]
  then
    export ramdiskName=$(osascript -e 'return text returned of (display dialog "RAM disk name" default answer "ramdisk")')
    if [ "$ramdiskName" == "" ] 
    then
      ramdiskName="ramdisk"
    fi
  
    echo Creating RAM disk $ramdiskName of size $ramdiskSizeMB MB with FS type $fsType
    hdidOutput=$(hdid -nomount ram://$((2048*ramdiskSizeMB)) | cut -d ' ' -f 1) && diskutil erasedisk "$fsType" "$ramdiskName" $hdidOutput
  fi
fi