what I did: Installed latest version of ispconfig with debian 13 support, everything still was fine. Upgraded to debiaian 13 following https://fullmetalbrackets.com/blog/upgrade-debian-12-bookworm-debian-13-trixie/ starting ispconfig get the error see subject. I will go back to backup before uograde debian.
Have you updated ISPConfig after you upgraded Debian? Without posting the error message, it's impossible to help you.
Have you updated ISPConfig after you upgraded Debian? No should I? it was Apache who gave me The internal server error
Post the error from the logs (both Apache and PHP and maybe system) That will tell why Apache gives you the internal server error.
Yes, you must update ISPConfig after you upgrade Debian. See the Debian + ISPConfig upgrade guides here at Howtoforge. They are not for Debian 13 yet, but it should be a very similar procedure.
Did a new try, situation before Debian 12 latest patsches ISPcomfig latest updated installed Upgrade Debin 12 to 13 likelast time Reboot did cd /tmp wget https://www.ispconfig.org/downloads/ISPConfig-3.3.1.tar.gz tar xvfz ISPConfig-3.3.1.tar.gz cd ispconfig3_install/install php -q update.php Start ISPcponfig brings Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator at webmaster@localhost to inform them of the time this error occurred, and the actions you performed just before this error. More information about this error may be available in the server error log. latest lines from error log [Sat Jan 24 08:39:11.976639 2026] [:notice] [pid 1007:tid 1007] mod_python: using mutex_directory /tmp [ N 2026-01-24 08:39:11.9904 968/T1 age/Cor/TelemetryCollector.h:531 ]: Message from Phusion: End time can not be before or equal to begin time [ N 2026-01-24 08:39:12.0235 968/T1 age/Cor/CoreMain.cpp:1322 ]: Passenger core shutdown finished [Sat Jan 24 08:39:12.049410 2026] [mpm_prefork:notice] [pid 1007:tid 1007] AH00163: Apache/2.4.66 (Debian) mod_fcgid/2.3.9 Phusion_Passenger/6.0.26 OpenSSL/3.5.4 mod_python/3.5.0.6 Python/3.13.5 configured -- resuming normal operations [Sat Jan 24 08:39:12.049477 2026] [core:notice] [pid 1007:tid 1007] AH00094: Command line: '/usr/sbin/apache2' [ N 2026-01-24 08:39:14.1221 1045/T6 age/Cor/SecurityUpdateChecker.h:519 ]: Security update check: no update found (next check in 24 hours) .php-fcgi-starter: 6: exec: /usr/bin/php-cgi: not found [Sat Jan 24 08:40:13.270699 2026] [fcgid:warn] [pid 1082:tid 1082] (104)Connection reset by peer: [client 172.16.1.200:55929] mod_fcgid: error reading data from FastCGI server, referer: https://isp-master.gerdakloos.de:8080/login/ [Sat Jan 24 08:40:13.270843 2026] [core:error] [pid 1082:tid 1082] [client 172.16.1.200:55929] End of script output before headers: index.php, referer: https://isp-master.gerdakloos.de:8080/login/ .php-fcgi-starter: 6: exec: /usr/bin/php-cgi: not found [Sat Jan 24 08:41:38.703653 2026] [fcgid:warn] [pid 1082:tid 1082] (104)Connection reset by peer: [client 172.16.1.200:56079] mod_fcgid: error reading data from FastCGI server [Sat Jan 24 08:41:38.703725 2026] [core:error] [pid 1082:tid 1082] [client 172.16.1.200:56079] End of script output before headers: index.php root@isp-master:/var/log/apache2#
think its a PHP problem. Tryed to install php Versions as from here https://www.howtoforge.com/update-the-ispconfig-perfect-server-from-debian-11-to-debian-12/ but get E: Package 'php8.2-cli' has no installation candidate E: Package 'php8.2-cgi' has no installation candidate E: Package 'php8.2-fpm' has no installation candidate E: Package 'php8.2-gd' has no installation candidate E: Package 'php8.2-mysql' has no installation candidate E: Package 'php8.2-imap' has no installation candidate E: Package 'php8.2-curl' has no installation candidate E: Package 'php8.2-intl' has no installation candidate E: Package 'php8.2-pspell' has no installation candidate E: Package 'php8.2-sqlite3' has no installation candidate E: Package 'php8.2-tidy' has no installation candidate E: Package 'php8.2-xsl' has no installation candidate E: Package 'php8.2-zip' has no installation candidate E: Package 'php8.2-mbstring' has no installation candidate E: Package 'php8.2-soap' has no installation candidate E: Package 'php8.2-opcache' has no installation candidate E: Package 'php8.2-common' has no installation candidate E: Package 'php8.2-readline' has no installation candidate E: Package 'php8.2-xml' has no installation candidate root@isp-master:/var/log/apache2#
Seems as if you uninstalled php. Debian 13 uses PHP 8.4 and not 8.2, so you must install that version: apt install php8.4-cgi php8.4-fpm Replace the 8.2 with 8.4 in the commands you used.
php8.4-imap is missing from trixie, I have similar issue with panel after installing on Debian 13, let's wait for guide maybe install script will supporte debian 13 better.
This thread here is about Debian 12 to 13 update, not installation on Debian 13. The ISPConfig install script is not used for Debian upgrades.
Yes, I also point out issues with installing it fresh - that's why waiting for now is better until all issues are resolved
