Free SSL Certificate with Let's Encrypt

1. Install git
apt-get install git

2. Create Let's Encrypt source directory
mkdir /opt/letsencrypt

3. Clone source of Let's Encrypt
git clone https://github.com/letsencrypt/letsencrypt /opt/letsencrypt

4. Stop web server (apache, tomcat, nginx...) because they can cause of port 443 error

5. Create certificate for specified domain
cd /opt/letsencrypt 
./letsencrypt-auto certonly --standalone -d example.com -d www.example.com

6. All certificates have created in /etc/letsencrypt/live

7. Config fullchain.pem for certificate file, privkey.pem for key file

For HaProxy, create .pem file
cat fullchain.pem privkey.pem > secure.pem

By default, Let's Encrypt issue certificate valid for 90 days, so we need config automatically renew it

1. create auto_renew_cert.sh file as below:
cd /opt/letsencrypt
git pull
service nginx stop
./letsencrypt-auto certonly --quiet --standalone --renew-by-default -d example.com
service nginx start

2.  execute it in crontab monthly
echo '@monthly root sh /root/auto_renew_cert.sh >> /var/log/letsencrypt/letsencrypt-auto-update.log' | sudo tee --append /etc/crontab

Portable Postgres

Postgres full extension 9.6.3 on Debian 8 64bit 
https://drive.google.com/open?id=0B30EeVPAcvhvWHpMNDZmbFdNYVk

Install Redmine

gem install passenger --no-ri --no-rdoc
passenger-install-nginx-module

http://coderazzi.net/linux/debian/redmine.htm

Function slower than query direct Postgres

For queries on tables with even data distribution, this will generally be no problem and PL/pgSQL functions will perform somewhat faster than raw SQL queries or SQL functions. But if your query can use certain indexes depending on the actual values in the WHERE clause or, more generally, chose a better query plan for the particular values, you may end up with a sub-optimal query plan.
(source: http://stackoverflow.com/questions/9305133/why-does-postgresql-treat-my-query-differently-in-a-function)

RETURN QUERY : cache plan
RETURN QUERY EXECUTE: replan for each call

RETURN QUERY EXECUTE $$
//query body
$$ USING param1, param2

Set static DNS using Ubuntu Deskop 16.04

nano /etc/resolvconf/resolv.conf.d/head

nameserver 8.8.8.8

Panel border shadow is black when sleep or suspend

If you use Unity, just open terminal and type

unity

everything should be ok!

Connect internet when using OpenVPN - Ubuntu 16.04

1. Setup OpenVPN using network manager

2. Open termainal, type

default_gateway=$(/sbin/ip route | awk '/default/ { print $3 }')
arr=(`echo ${default_gateway}`);
#echo "${arr[1]}"
sudo route add default gw "${arr[1]}"  wlp62s0
sudo route add -net 10.0.0.0 netmask 255.255.255.0 dev tun0

wlp620: main card connect internet (wifi or cable)
tun0: virtual interface of VPN connection
10.0.0.0 : base ip of VPN connection (ex: 10.0.0.3)


3. Save as changegateway
4. chmod +x changegateway
5. ./changegateway