All posts by Malte

How I run small websites in Docker-containers separated from each other on a small VPS

Since I rarely give insights on how websites such as this one are run, I decided it would be a great time to share one very simplistic and efficient approach to host several small websites, separated from each other, on a cheap VPS.

When we talk websites, I mean WordPress instances. WordPress has a few basic requirements:

  • the PHP scripting-language
  • a MySQL database
  • possiblity to use sendmail or a similar software to send mails

To achieve these basic requirements, I employ:

  • one docker-compose stack bundling the MySQL-database as well as the phpMyAdmin-webinterface
  • multiple docker-compose stacks bundling PHP-FPM, nginx as well as exim4 to act as a mailrelay
  • one nginx instance on the VPS (uncontainered as of now) that does the SSL-offloading and acts as a reverse proxy in front of the different docker-compose stacks for WordPress

The setup is:

  • simple
  • easy to handle (upgrades, PHP-version switching etc.)
  • efficient (especially towards RAM usage)
  • easily migrateable to a different machine
Continue reading How I run small websites in Docker-containers separated from each other on a small VPS

cryptsetup “No key available with this passphrase.” even though you are 100% certain its the right key (Debian Buster)

Something I stumbled upon today. I tried to unlock a LUKS container and was 100% certain that the passphrase is correct. Still, cryptsetup would not unlock the container:

# cryptsetup luksOpen /container_file container
Enter passphrase for /container_file: 
No key available with this passphrase.

Digging around, references can be found to either a problem with the character encoding of the shell or to a bug with cryptsetup and Samsung EVO SSDs with certain older 5.1 kernels. None of these were the case.

After some trial and error, I upgraded the cryptsetup packages from 2:2.1.0-5+deb10u2 (from buster/main repo) to 2:2.3.5-1~bpo10+1 (buster-backports/main repo). Suddenly the container would unlock.

I think most of the time people either get their passphrase wrong or their header was corrupted somehow, but in this case: Some bug in cryptsetup. (Not reported yet, no existing report found yet.)

Sync time on Linux via GSM

The RaspberryPi and many similar single-board computers do not have an RTC or “Real Time Clock” and without internet connectivity cannot retain their time setting. Therefore most RaspberryPi Linux-distributions employ NTP to sync the time right after boot. If you are not able to use an internet connection and therefore no NTP, but have a GSM modem or phone and a valid sim card at hand, this guide may be suitable for your needs.

Continue reading Sync time on Linux via GSM

Change Plesk spam-settings in bulk

Since Plesk per default uses the static userdb-driver of Dovecot, it may seem difficult to easily iterate through all mailboxes on the server, for example in order to change the spam-settings of all mailboxes on the systems at once while keeping the “individual settings per-mailbox” functionality enabled.

The following one-liner may be helpful in such case:

while read domain; do (while read user; do plesk bin spamassassin --update $user@$domain -status true -personal-conf true -action move -hits 6; done < <(ls -1 /var/qmail/mailnames/$domain)); done < <(ls -1 /var/qmail/mailnames/)

In this case, the domains and mailboxes are placed in/var/qmail due to a previous upgrade from qmail to Dovecot. If the directory in your case differs, make sure to change it in the one-liner, too.