Search notes:

/proc/sys/kernel/osrelease

cat /proc/sys/kernel/osrelease might print something like 
Linux
In a Kernel running under Windows Subsystem for Linux, it prints 
$ sudo cat /proc/sys/kernel/osrelease
6.1.21.2-microsoft-standard-WSL2+

See also

/proc/sys/kernel/ostype
/proc/version

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...', 1738302944, '18.224.32.70', 'Mozilla/5.0 App...', NULL) #2 /home/httpd/vhosts/renenyffenegger.ch/httpsdocs/notes/Linux/fhs/proc/sys/kernel/osrelease(45): insert_webrequest() #3 {main} thrown in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php on line 78