Alexfilus

# The VirtualBox documentation[1] for how to install guest additions 
# for Linux on a virtual host is somewhat messy. So here is what 
# I did to make it work.

# Install the packages required
yum update
yum install gcc kernel-devel make

reboot

Alexfilus

useradd -m -c "Admin User" lord
passwd lord
usermod -aG sudo lord
sudo nano /etc/ssh/sshd_config
PermitRootLogin yes -> no
systemctl restart sshd

Alexfilus

session_start([
    'save_handler' => 'redis',
    'save_path' => 'tcp://127.0.0.1:6379?database=1',
    'cookie_lifetime' => 86400,
    'gc_maxlifetime' => 86400,
    'serialize_handler' => 'igbinary',
    'name' => 'project',
    'cookie_httponly' => true
]);

Alexfilus

Adjusting child processes for PHP-FPM (Nginx)

When setting these options consider the following:

• How long is your average request?
• What is the maximum number of simultaneous visitors the site(s) get?
• How much memory on average does each child process consume?

Determine if the max_children limit has been reached.

• sudo grep max_children /var/log/php?.?-fpm.log.1 /var/log/php?.?-fpm.log

Alexfilus

sudo docker run --detach \
  --hostname gitlab.example.com \
  --publish 8443:443 --publish 8080:80 --publish 2222:22 \
  --name gitlab \
  --restart always \
  --volume /srv/gitlab/config:/etc/gitlab \
  --volume /srv/gitlab/logs:/var/log/gitlab \
  --volume /srv/gitlab/data:/var/opt/gitlab \
 gitlab/gitlab-ce:latest

Alexfilus

/usr/lib/postgresql/12/bin/pg_upgrade \
  --old-datadir=/var/lib/postgresql/10/main \
  --new-datadir=/var/lib/postgresql/12/main \
  --old-bindir=/usr/lib/postgresql/10/bin \
  --new-bindir=/usr/lib/postgresql/12/bin \
  --old-options '-c config_file=/etc/postgresql/10/main/postgresql.conf' \
  --new-options '-c config_file=/etc/postgresql/12/main/postgresql.conf' \
  --check

Alexfilus

psql -U postgres -d name -h host.com -p 5432 -c "COPY (SELECT id, name FROM user LIMIT 10) TO STDOUT With CSV HEADER DELIMITER ',';" > foo_data.csv

Alexfilus

    /**
     * @param string $range
     * @return string
     */
    public static function cleanRange(string $range): string
    {
        return preg_replace('/[^0-9\-,]/', '', $range);
    }

    /**

Alexfilus

SELECT table,
    formatReadableSize(sum(bytes)) as size,
    min(min_date) as min_date,
    max(max_date) as max_date
    FROM system.parts
    WHERE active
GROUP BY table

Alexfilus

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD