Search notes:

/etc/adjtime

The configuration and state file for hwclock (aka adjtime file). It keeps track of the systematic drift of the hardware clock.
I had to create this file by executing 
sudo hwclock --systohc
The /etc/adjtime file might look as follows: 
0.000000 1492635067 0.000000
1492635067
UTC

FHS

Apparently, the FHS recommends to store the adjtimefile in /var/lib/hwclock instead of the usual /etc/adjtime.

See also

NTP

Index

Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php:78 Stack trace: #0 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(78): PDOStatement->execute(Array) #1 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(30): insert_webrequest_('/notes/Linux/fh...', 1745762801, '18.221.176.186', 'Mozilla/5.0 App...', NULL) #2 /home/httpd/vhosts/renenyffenegger.ch/httpsdocs/notes/Linux/fhs/etc/adjtime(51): insert_webrequest() #3 {main} thrown in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php on line 78