Storage efficient backup with rsync on Linux

How I backup my home directory on Linux with rsync

My requirements

The backup script

This is my shell script:


today=$(date +%Y-%m-%d)

rsync -av --delete --exclude-from=/home/oli/rsync-homedir-excludes/rsync-homedir-excludes.txt \
        "${source}"  "${target}${today}/" --link-dest="${target}last/"

ln -nsf "${target}${today}" "${target}last"

exit 0

How to use


The backup will create a new folder for the current date in the target directory:

drwxr-xr-x 52 oli oli 4096 Mai  1 13:23 2021-05-01
drwxr-xr-x 52 oli oli 4096 Mai  2 08:14 2021-05-02
drwxr-xr-x 52 oli oli 4096 Mai 13 09:26 2021-05-13
drwxr-xr-x 52 oli oli 4096 Mai 16 09:27 2021-05-16
drwxr-xr-x 52 oli oli 4096 Mai 23 08:27 2021-05-23
drwxr-xr-x 52 oli oli 4096 Jul 25 08:52 2021-07-25
drwxr-xr-x 52 oli oli 4096 Aug  8 09:19 2021-08-08
lrwxrwxrwx  1 oli oli   58 Aug  8 09:39 last -> /media/oli/Seagate_4TB/Backup/vostro/rsync-tool/2021-08-08

Every folder will contain a full copy of the source directory at the respective date, but will require just the storage space of the new and changed files. All unchanged files will be hard-linked, so they will just use an inode.

Even on my 10 years old Laptop with USB 2.0 the backup of the home partition takes just some minutes, due to the efficiency of rsync


sent 142,744,045 bytes  received 44,245 bytes  574,600.76 bytes/sec
total size is 266,349,471,150  speedup is 1,865.35

Fast and efficient backup of XFS partition

If you are using the XFS filesystem for your Linux partition you can create full and incremental backups with the powerful tool xfsdump.

I am creating a backup of my home partition like this:

sudo xfsdump -l 0 -L "Backup level 0 of /home `date`" - /home | lzop > /backup-dir/home-xfsdump-`date +%Y-%m-%d`.lzo

Let’s have a detailed look on the used commands and parameters:

lzop will compress the filesystem data with minimal CPU usage and not slowing down your backup procedure at all, the limiting bottleneck will probably be your backup storage (external USB drive or network storage):

xfsdump load

You probably have to install xfsdump and lzop first:

sudo apt install xfsdump lzop

Now you also have the xfsrestore command, which you will need to restore the filesystem from the backup:

lzop -dc my-xfsdump.lzo | xfsrestore - /home

With xfsdump you can even do incremental backups, Red Hat has a comprehensive article about BACKING UP AND RESTORING XFS FILE SYSTEMS

Performance improvements with PHP 8 JIT compiler

PHP 8.0.0 introduced a new “just in time” compiler (JIT) that can improve the performance of our PHP applications. But the JIT is not active by default. So how can the JIT compiler be activated and what is the performance gain?

These ini-file settings will activate the opcache and the JIT compiler with some more reasonable default settings:


We should now get some lines with configuration settings after running php -i | grep jit in the terminal:

auto_globals_jit => On => On
pcre.jit => 1 => 1
opcache.jit => tracing => tracing
opcache.jit_bisect_limit => 0 => 0
opcache.jit_blacklist_root_trace => 16 => 16
opcache.jit_blacklist_side_trace => 8 => 8
opcache.jit_buffer_size => 100M => 100M
opcache.jit_debug => 0 => 0
opcache.jit_hot_func => 127 => 127
opcache.jit_hot_loop => 64 => 64
opcache.jit_hot_return => 8 => 8
opcache.jit_hot_side_exit => 8 => 8
opcache.jit_max_exit_counters => 8192 => 8192
opcache.jit_max_loop_unrolls => 8 => 8
opcache.jit_max_polymorphic_calls => 2 => 2
opcache.jit_max_recursive_calls => 2 => 2
opcache.jit_max_recursive_returns => 2 => 2
opcache.jit_max_root_traces => 1024 => 1024
opcache.jit_max_side_traces => 128 => 128
opcache.jit_prof_threshold => 0.005 => 0.005

Here I want to test the performance gain with a small script, that will calculate the prime numbers up to 100 mio using an implementation of the Sieve of Eratosthenes. It will not output each prime number but rather count all the prime numbers up to the given upper limit.

$tStart = microtime(true);

$limit = 100_000_000;

$nums=array_fill(0, $limit+1, 1);
$sqrtlimit = (int)sqrt($limit);
for ($n = 2; $n <= $sqrtlimit; $n++)
  if (1 === $nums[$n])
    for ($i = $n * $n; $i <= $limit; $i += $n)
      $nums[$i] = 0;
$duration = microtime(true) - $tStart;

echo array_sum($nums)-2 . "\n"; // 0 and 1 are not primes
echo round($duration, 3) . " seconds\n";

I did a couple of test runs, with PHP 7.4 / 8.0, without opcache and with opcache, without and with JIT compiler and also with strict_mode:

PHP 7.4 and 8.0 performance

Running with PHP 8.0 and active JIT compiler

>php8.0 prime-sieve.php 
10.614 seconds

Seems like it doesn’t matter if we are running PHP 7.4 or PHP 8.0 with or without opcache. But activating the JIT compiler in PHP 8.0 gives us a 90% performance improvement! This is quite a remarkable boost, though in real life code the speed improvement will probably be much smaller, due to more I/O operations like database requests.

Performance comparison of Laravel cache stores

When running a high traffic website with Laravel, caching becomes a critical aspect for performance.

Using the Laravel framework it is possible to use different cache stores, e.g. file cache for development and Redis or Memcached for production servers.

So the question is, what is the best cache store for my use case? To answer this question, I wrote a small PHP script to be run with Laravel Tinker.

By default it will create 100 cache items and perform 20 times more reads than writes to all configured and available cache stores.

To run the Laravel cache benchmark, clone or download it from and copy the file cache-benchmark.php to the directory of your Laravel project. You may want to edit some settings in the top section of the file. e.g. disable memcache tests if this cache store is not available in your specific setup.

Open a terminal and in your project directory run:

php artisan tinker cache-benchmark.php

The tests will run for some seconds only, and no caches will be flushed, so it is safe to run on a production system too.

The results from my local Mac/Docker setup (PHP 7.4, Redis, Memcached, MariaDB) are:

array: 0.133 seconds, 15815 queries/sec
memcached: 0.517 seconds, 4061 queries/sec
redis: 0.736 seconds, 2853 queries/sec
database: 2.122 seconds, 990 queries/sec
file: 2.461 seconds, 853 queries/sec

Results from a small VPS (1 Xeon core, 1 GB RAM) are quite different:

array: 0.052 seconds, 40243 queries/sec
memcached: 0.13 seconds, 16175 queries/sec
redis: 0.159 seconds, 13209 queries/sec
database: 4.007 seconds, 524 queries/sec
file: 0.16 seconds, 13164 queries/sec

Surprisingly the file cache store is as fast as local Redis!

Conclusion: it is a good idea to benchmark the cache performance on a real system, instead of guessing and making assumptions.

40 times faster PHP Code Coverage Reporting with PCOV

For a PHP project with over 100 000 lines of code I want to create Code Coverage Reports on an regular basis, usually every 1 or 2 months.

With the Xdebug enabled such a run of phpunit --coverage-text=report.txt takes ages:

Time: 2.2 hours, Memory: 269.00 MB

OK, but incomplete, skipped, or risky tests!
Tests: 775, Assertions: 2825, Skipped: 1.

It takes more than 2 hours to create the Code Coverage Report!

By using the awesome PCOV PHP extension it was possible to accelerate the process by factor 40!

Time: 3.32 minutes, Memory: 259.00 MB

OK, but incomplete, skipped, or risky tests!
Tests: 775, Assertions: 2825, Skipped: 1.

With PCOV the Code Coverage Report was created in about 3 minutes only!

How to install PCOV in a PHP Docker image

In your PHP Dockerfile add these lines to a RUN directive

pecl install pcov && \
docker-php-ext-enable pcov

and then build your PHP Docker image as usual.

PCOV and Xdebug

Please keep in mind:
It is not possible to have Xdebug and PCOV both active at the same time! Xdebug must not be enabled, when PCOV is active.

If you want to debug your code with Xdebug, you first have do disable PCOV. Just set pcov.enabled=0 in a PHP ini file and don’t forget to restart your PHP-FPM or your Docker containers to apply the changes.

Check password strength with vanilla JavaScript and HTML5

Weak passwords are bad and a real danger. So we should encourage our users to use stronger passwords for their online accounts.

Therefore nowadays it is state of the art to give the user instant feedback about the password quality, e.g. on a registration form or a change-password form.

There are great out-of-the-box solutions to tackle this task, like

These packages can even check against known password lists and dictionaries. But on the downside they will add some additional 100kB to the javascript code or even require frameworks like jQuery or Bootstrap.

For my use case this would be too much. I don’t want to bother users with restrictive and complicated password rules. I just want to give a quick feedback about the password strength, based on a few simple rules. So I implemented my own very basic password strength indicator.

Given, we have an html form with a password input:

<input type="password" id="pwd" placeholder="enter password">

We now add a HTML5 progress bar to be used as a password strength indicator:

<progress id="strength" value="0" max="5"></progress>

Each of these elements have an id, so we can easily address it later via JavaScript.

Of course, now we also need a JavaScript function to evaluate the password, it should get the password string as a parameter and return a numeric value as a measure for the password strength.

function passwordStrength(pw) {
  return /.{8,}/.test(pw) * (  /* at least 8 characters */
    /.{12,}/.test(pw)          /* bonus if longer */
    + /[a-z]/.test(pw)         /* a lower letter */
    + /[A-Z]/.test(pw)         /* a upper letter */
    + /\d/.test(pw)            /* a digit */
    + /[^A-Za-z0-9]/.test(pw)  /* a special character */

In this function we check the password input against some regular expressions using the test() method and then treating the boolean return value as a number (0 or 1).

To get the top score of 5 a password must be at least 12 characters long and must have numbers, upper and lower letters and other special characters. Passwords shorter than 8 characters are considered insecure and will get a rating of 0.

Finally we just need some magic glue to connect all the bits and pieces properly. We want to evaluate the password whenever a key is pressed in the password input field and update the password strength indicator immediately:

let pwInput = document.getElementById("pwd")

pwInput.addEventListener('keyup', function() { 
 document.getElementById("strength").value = passwordStrength(pwInput.value)

Just have a try or see and edit the full source code at

Feel free to modify the password rules to your needs, add your own rules or some textual output to the user interface.

How to drastically increase Docker performance on Mac and Windows

On Windows and Mac you will probably see a poor performance for your thoroughly dockerized application. This is due to very slow storage I/O operations on your mounted volumes from the local filesystem. On Mac and Windows Docker file has to route file system operations through more layers compared to running Docker on Linux.

If using docker-compose there is a very easy way to speed up the file access and the whole application. Just use the mount options delegated or cached in your docker-compose.yml file like this:

version: '2'
    container_name: app
    image: php:7.3.8-fpm-stretch
    user: www-data
    working_dir: /var/www
      - ./:/var/www:delegated

    container_name: web
    image: nginx:1.13-alpine
    working_dir: /var/www/html
      - "80:80"
      - ./:/var/www/html:ro,delegated
      - ./docker/nginx.conf:/etc/nginx/conf.d/default.conf:ro

On my Mac I use the option delegated and the speedup of the application is about 140%, the runtime of PHPUnit dropped from about 4.0 minutes to 1.7!

Please read the docs for more information and consequences.

Reset and sync local git repository with remote branch

Messed up your local files and git repo?
Just clean up the mess and make it like the remote master branch again:

git fetch origin
git reset --hard origin/master
git clean -f -d

Your local branch is now an exact copy of the remote branch.

How to create a MySQL/MariaDB database and user

When you want to create a new Database for MySQL or MariaDB and an extra DB user for it:

CREATE USER 'newuser'@'localhost' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON MYNEWDB.* TO 'newuser'@'localhost';

This will create a general purpose database user, that can not only read and write data, but also modify the structure of the database, like ALTER or DROP tables.