Raspberry pi best heatsink comparison benchmark


Raspberry Pi manufacturer have stated you don’t need heatsink for the normal operation of the Raspberry Pi device, however overclocked or heavily stressed devices will benefit from heatsink installation.
I decided to compare available heatsinks on the market and have found the best heatsink for Raspberry Pi 3.

First tested heatsink is small – 14x14x6mm, priced 1$ on Ebay
It has an adhesive layer for mounting on CPU.


Second heatsink – is larger 50x25x10mm, also priced 1$


Mounting was done with Arctic Silver thermal compound and и super-glue 🙂 Thermal compound was applied to the center and glue – to the corners of the chip.
Please note that this will be a permanent solution, and you will not be able to remove the heatsink.

For loading the CPU I used stress software (apt-get install stress).
Only 1 core of Raspberry Pi 3 was loaded – frequencies: arm_freq=1290 core_freq=430

Here are the temperature graphs:


Red line – no heatsink.
Blue – small heatsink 14х14
Gren – large heatsink 50х25

For a price of 1$ you can greatly improve temperature of Raspberry Pi 3 – by 8 degrees in idle state and by 13 degrees under moderate load.

transaction check error – mysql-community-libs-compat conflicts with file from package compat-mysql51

While upgrading MySQL server on centos 6 from 5.5 to 5.7 you may encounter following error:

Transaction Check Error:
  file /usr/lib64/mysql/libmysqlclient.so.16.0.0 from install of mysql-community-libs-compat-5.7.11-1.el6.x86_64 conflicts with file from package compat-mysql51-5.1.54-1.el6.remi.x86_64
  file /usr/lib64/mysql/libmysqlclient_r.so.16.0.0 from install of mysql-community-libs-compat-5.7.11-1.el6.x86_64 conflicts with file from package compat-mysql51-5.1.54-1.el6.remi.x86_64

It can be resolved by running following yum transaction:

$ yum shell
> remove compat-mysql51
> install mysql-community-libs-compat
> run

This will update affected mysql libraries to newer version without breaking any dependencies.

Remove all store apps windows 10


If you don’t use new (modern / metro) style application in windows you can delete all of them with a single PowerShell command.
To open PowerShell: Right click on Windows logo -> Command Prompt (Administrator – type powershell and press Enter.

This command removes all store apps for currently logged in user.

Get-AppxPackage | Remove-AppxPackage

To delete installation packages from disk and prevent installation for new users:
WARNING! This cannot be undone, you will lose ability to install new apps from Windows Store.

Get-AppXProvisionedPackage -Online | Remove-AppxProvisionedPackage -Online

ISPconfig / dovecot – send mailbox quota warning to users

To alert users, that are approaching theirs mailbox quota limit you can use built in Dovecot plugin quota_warning.

1. Edit the main Dovecot configuration file:

plugin {
  quota = dict:user::file:/var/vmail/%d/%n/.quotausage

  # Do not change existing plugins defined above, just add new entries below

  quota_warning = storage=95%% quota-warning 95 %u
  quota_warning2 = storage=80%% quota-warning 80 %u
  quota_warning3 = -storage=100%% quota-warning below %u # user is no longer over quota

service quota-warning {
  executable = script /usr/local/bin/quota-warning.sh
  user = vmail
  unix_listener quota-warning {
        user = vmail
        mode = 0600

This will execute defined script /usr/local/bin/quota-warning.sh when user will exceed 80 and 95% of their mailbox space.

2. Create the alerting script:

cat << EOF | /usr/libexec/dovecot/dovecot-lda -d $USER -o "plugin/quota=maildir:User quota:noenforcing"
From: postmaster@localhost.local
Subject: Mailbox size warning

Your mailbox is now $PERCENT% full. Please delete old messages.

You may edit the text to better explain required steps to resolve this issue.

OpenSSL check p12 expiration date

1. Check .p12 / .pfx certificate expiration date:

openssl pkcs12 -in testuser1.pfx -nokeys | openssl x509 -noout -enddate

To specify password in plain text, add -passin pass:”${pass}”

2. Export key and cert from .p12 / .pfx:

openssl pkcs12 -clcerts -nokeys -in myContainer.p12 -out usercert.pem
openssl pkcs12 -nocerts  -in myContainer.p12 -out userkey.pem

3. Connect to HTTPS server with client certificate:

openssl s_client -connect gmail.com:443 -cert usercert.pem -key userkey.pem