QRencode

Забавна программа якщо треба перенести якийсь текст на телефон, а під рукою нема ніяких штатних месенджерів

echo "text_string" | qrencode -t UTF8 -o - 
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████ ▄▄▄▄▄ █▀▄█▀▄█ ▄▄▄▄▄ ████
████ █   █ █▀▄█▀██ █   █ ████
████ █▄▄▄█ █▀▀ ▄ █ █▄▄▄█ ████
████▄▄▄▄▄▄▄█▄█ ▀ █▄▄▄▄▄▄▄████
████ ▄▄▄ ▀▄▄  ██ ▄█▄▀ ▀▄▀████
█████▀▄▄▄█▄█▀█▀▄█▀▄▀█  ▄█████
████▄▄▄▄█▄▄▄ ▀▄▄▀█ █▀▄█ ▀████
████ ▄▄▄▄▄ █▄ ▄█▄ ██▀▀ ▄█████
████ █   █ █ ▄ █▀▀ ▄▀ ▀▄▄████
████ █▄▄▄█ █ ▄▀▀▄▀▄█▀▀ ██████
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SSH client stuck on connect

This is probably an issue with D-Bus and systemd. If the dbus service is restarted for some reason, you will also need to restart systemd-logind
restart systemd-logind service:

systemctl restart systemd-logind

I had this same issue on CentOS 7, because the messagebus was restarted (which is how the D-Bus service is called on CentOS).

Linux bridge: MAC addresses and dynamic ports

Scenario: KVM virtualization host running several bridged guests. The host has a bridge interface br0 that starts out containing only eth0, and other interfaces are dynamically added and removed from the bridge as guests are started and stopped.
The problem is, the host seems to randomly suffer some loss of connectivity (from a few to 30-40 seconds) when some guest is started or stopped. Initially one might think of something related to STP, but it turns out that it is disabled (and even then, ports appearing or disappearing should not affect existing ports).

What happens here is that, when a new guest is started, a tap interface is created and enslaved to the bridge (the tap interface is usually connected to the guest’s own ethernet interface). This interface has a name like vnet5, for example. Minor but important detail, this tap interface has a more or less random MAC address. (Note that we’re talking of the host-side tap interface, not the guest-side virtual interface, whose MAC address is configurable in the guest’s configuration file or on the command line). It is theoretically possible to set the MAC address of this host-side tap interface, but it’s quite involved and basically nobody does that (and also virt-manager has no provision to do that).

Now, by default bridge interfaces in Linux use, for their MAC address, the lowest MAC address among the enslaved interfaces. So if the newly created interface has a lower MAC, the bridge changes its MAC address and uses that of the new interface. When the guest is stopped, the tap interface is removed from the bridge and destroyed, at which point the bridge’s MAC address has to change again. Depending on when and how often guests are started/stopped, the host’s bridge interface may be changing its MAC address quite often.

Of course, this may (and does) cause connectivity problems for traffic to/from the host (fortunately, traffic to/from the guests is not affected), because neighboring computers and network devices suddenly have to update their ARP caches with the new MAC address before they can talk to the host. Depending on the traffic patterns, this may take anything from a few seconds to several tens of seconds.
Читать далее Linux bridge: MAC addresses and dynamic ports

Mysql: wrong slave_master_info after upgrade to 5.7

After upgrade mysql-server from 5.6 to 5.7.10 something strange going on with multimaster replication.
When you add more then one channel replication tool not see second channel and server hangs on first channel.
This happens because mysql_upgrade tool have a bug. This bug create columns in table slave_master_info in wrong order.
Читать далее Mysql: wrong slave_master_info after upgrade to 5.7

Add CA certifice from Let’s Encrypt to Java 8

For add cert to Java 8 you need use keytool

cd /tmp/ && \
curl -O https://letsencrypt.org/certs/letsencryptauthorityx1.der && \
sudo $JAVA_HOME/bin/keytool -noprompt -importcert -alias letsencryptauthorityx1 -keystore $JAVA_HOME/jre/lib/security/cacerts -file  letsencryptauthorityx1.der  -storepass changeit && \
curl -O https://letsencrypt.org/certs/lets-encrypt-x3-cross-signed.der && \
sudo $JAVA_HOME/bin/keytool -noprompt -importcert -alias lets-encrypt-x3-cross-signed -keystore $JAVA_HOME/jre/lib/security/cacerts -file lets-encrypt-x3-cross-signed.der -storepass changeit

Читать далее Add CA certifice from Let’s Encrypt to Java 8

Syncthing: Debian run script

syncthing
Rename syncthing.txt to syncthing
Put to /etc/init.d/
Change USER and DAEMON vars

 chmod 755 /etc/init.d/syncthing

To run Syncthing :

sudo service syncthing start

For autostart

sudo update-rc.d syncthing defaults

Certificate order in Haproxy PEM file

For SSL in Haproxy you need to create PEM-file and put cert plus private key. But in right order

-----BEGIN MY CERTIFICATE-----
-----END MY CERTIFICATE-----
-----BEGIN INTERMEDIATE CERTIFICATE-----
-----END INTERMEDIATE CERTIFICATE-----
-----BEGIN INTERMEDIATE CERTIFICATE-----
-----END INTERMEDIATE CERTIFICATE-----
-----BEGIN ROOT CERTIFICATE-----
-----END ROOT CERTIFICATE-----
-----BEGIN RSA PRIVATE KEY-----
-----END RSA PRIVATE KEY-----

Java8 in Debian

For starting we need install add-apt-repository

apt-get install software-properties-common python-software-properties

Then install java8

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer

To automatically set up the Java 8 environment variables:

sudo apt-get install oracle-java8-set-default

or

echo "deb http://ppa.launchpad.net/webupd8team/java/ubuntu xenial main" | tee /etc/apt/sources.list.d/webupd8team-java.list
echo "deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu xenial main" | tee -a /etc/apt/sources.list.d/webupd8team-java.list
apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys EEA14886
apt-get update
apt-get install oracle-java8-installer

avconv: simple video converter in Linux

If you want convert video from big size to smartphone size use this Libav tool
Ubuntu:

apt-get install libav-tools

or Gentoo

USE="mp3 speex threads v4l jpeg2k aac amr cpudetection faac opus vdpau x264 webp  x265 xvid " CPU_FLAGS_X86="mmx mmxext sse sse2 sse3 sse4_1"  emerge -av libav

and command for convert

avconv -i original_video.mkv -b:v 600k -s 576x432 -strict experimental small_size.mp4