These are the error messages from koha-error.log, the headlines describes the actions in the UI (I retranslate from the German UI to English): 1. open the koha adminstration site [Sat Jun 03 20:37:10.059931 2017] [cgi:error] [pid 7937] [client 192.168.0.12:54200] AH01215: [Sat Jun 3 20:37:10 2017] mainpage.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/mainpage.pl [Sat Jun 03 20:37:10.063881 2017] [cgi:error] [pid 7937] [client 192.168.0.12:54200] AH01215: [Sat Jun 3 20:37:10 2017] mainpage.pl: DBD::mysql::st execute failed: MySQL server has gone away [ for Statement " SELECT `me`.`borrowernumber`, `me`.`cardnumber`, `me`.`surname`, `me`.`firstname`, `me`.`title`, `me`.`othernames`, `me`.`initials`, `me`.`streetnumber`, `me`.`streettype`, `me`.`address`, `me`.`address2`, `me`.`city`, `me`.`state`, `me`.`zipcode`, `me`.`country`, `me`.`email`, `me`.`phone`, `me`.`mobile`, `me`.`fax`, `me`.`emailpro`, `me`.`phonepro`, `me`.`B_streetnumber`, `me`.`B_streettype`, `me`.`B_address`, `me`.`B_address2`, `me`.`B_city`, `me`.`B_state`, `me`.`B_zipcode`, `me`.`B_country`, `me`.`B_email`, `me`.`B_phone`, `me`.`dateofbirth`, `me`.`branchcode`, `me`.`categorycode`, `me`.`dateenrolled`, `me`.`dateexpiry`, `me`.`gonenoaddress`, `me`.`lost`, `me`.`debarred`, `me`.`debarredcomment`, `me`.`contactname`, `me`.`contactfirstname`, `me`.`contacttitle`, `me`.`guarantorid`, `me`.`borrowernotes`, `me`.`relationship`, `me`.`sex`, `me`.`password`, `me`.`flags`, `me`.`userid`, `me`.`opacnote`, `me`.`contactnote`, `me`.`sort1`, `me`.`sort2`, `me`.`altcontactfirstname`, `me`.`altcontactsurname`, `me`.`altcontactaddress1`, `me`.`altcontactaddress2`, `me`.`altcontactaddress3`, `me`.`altcontactstate`, `me`.`altcontactzipcode`, `me`.`altcontactcountry`, `me`.`altcontactphone`, `me`.`smsalertnumber`, `me`.`sms_provider_id`, `me`.`privacy`, `me`.`privacy_guarantor_checkouts`, `me`.`checkprevcheckout`, `me`.`updated_on`, `me`.`lastseen` FROM `borrowers` `me` WHERE ( `me`.`userid` = ? ) " with ParamValues: 0="krieg" ] at /usr/share/perl5/vendor_perl/DBIx/Class/Storage/DBI.pm line 1836.: /var/www/koha/intranet/cgi-bin/mainpage.pl [Sat Jun 03 20:37:10.099014 2017] [cgi:error] [pid 7937] [client 192.168.0.12:54200] AH01215: [Sat Jun 3 20:37:10 2017] mainpage.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/mainpage.pl [Sat Jun 03 20:37:10.100329 2017] [cgi:error] [pid 7937] [client 192.168.0.12:54200] AH01215: [Sat Jun 3 20:37:10 2017] mainpage.pl: DBD::mysql::st execute failed: MySQL server has gone away [ for Statement " SELECT `me`.`variable`, `me`.`value`, `me`.`options`, `me`.`explanation`, `me`.`type` FROM `systempreferences` `me` WHERE ( `me`.`variable` = ? ) " with ParamValues: 0="dateformat" ] at /usr/share/perl5/vendor_perl/DBIx/Class/Storage/DBI.pm line 1836.: /var/www/koha/intranet/cgi-bin/mainpage.pl 2. click on button "Tools" [Sat Jun 03 20:55:29.710380 2017] [cgi:error] [pid 7924] [client 192.168.0.12:54232] AH01215: [Sat Jun 3 20:55:29 2017] tools-home.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/tools/tools-home.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/mainpage.pl [Sat Jun 03 20:55:29.713915 2017] [cgi:error] [pid 7924] [client 192.168.0.12:54232] AH01215: [Sat Jun 3 20:55:29 2017] tools-home.pl: DBD::mysql::st execute failed: MySQL server has gone away [ for Statement " SELECT `me`.`borrowernumber`, `me`.`cardnumber`, `me`.`surname`, `me`.`firstname`, `me`.`title`, `me`.`othernames`, `me`.`initials`, `me`.`streetnumber`, `me`.`streettype`, `me`.`address`, `me`.`address2`, `me`.`city`, `me`.`state`, `me`.`zipcode`, `me`.`country`, `me`.`email`, `me`.`phone`, `me`.`mobile`, `me`.`fax`, `me`.`emailpro`, `me`.`phonepro`, `me`.`B_streetnumber`, `me`.`B_streettype`, `me`.`B_address`, `me`.`B_address2`, `me`.`B_city`, `me`.`B_state`, `me`.`B_zipcode`, `me`.`B_country`, `me`.`B_email`, `me`.`B_phone`, `me`.`dateofbirth`, `me`.`branchcode`, `me`.`categorycode`, `me`.`dateenrolled`, `me`.`dateexpiry`, `me`.`gonenoaddress`, `me`.`lost`, `me`.`debarred`, `me`.`debarredcomment`, `me`.`contactname`, `me`.`contactfirstname`, `me`.`contacttitle`, `me`.`guarantorid`, `me`.`borrowernotes`, `me`.`relationship`, `me`.`sex`, `me`.`password`, `me`.`flags`, `me`.`userid`, `me`.`opacnote`, `me`.`contactnote`, `me`.`sort1`, `me`.`sort2`, `me`.`altcontactfirstname`, `me`.`altcontactsurname`, `me`.`altcontactaddress1`, `me`.`altcontactaddress2`, `me`.`altcontactaddress3`, `me`.`altcontactstate`, `me`.`altcontactzipcode`, `me`.`altcontactcountry`, `me`.`altcontactphone`, `me`.`smsalertnumber`, `me`.`sms_provider_id`, `me`.`privacy`, `me`.`privacy_guarantor_checkouts`, `me`.`checkprevcheckout`, `me`.`updated_on`, `me`.`lastseen` FROM `borrowers` `me` WHERE ( `me`.`userid` = ? ) " with ParamValues: 0="krieg" ] at /usr/share/perl5/vendor_perl/DBIx/Class/Storage/DBI.pm line 1836.: /var/www/koha/intranet/cgi-bin/tools/tools-home.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/mainpage.pl [Sat Jun 03 20:55:29.898190 2017] [cgi:error] [pid 7924] [client 192.168.0.12:54232] AH01215: [Sat Jun 3 20:55:29 2017] tools-home.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/tools/tools-home.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/mainpage.pl [Sat Jun 03 20:55:29.899380 2017] cgi:error] [pid 7924] [client 192.168.0.12:54232] AH01215: [Sat Jun 3 20:55:29 2017] tools-home.pl: DBD::mysql::st execute failed: MySQL server has gone away [ for Statement " SELECT `me`.`variable`, `me`.`value`, `me`.`options`, `me`.`explanation`, `me`.`type` FROM `systempreferences` `me` WHERE ( `me`.`variable` = ? ) " with ParamValues: 0="dateformat" ] at /usr/share/perl5/vendor_perl/DBIx/Class/Storage/DBI.pm line 1836.: /var/www/koha/intranet/cgi-bin/tools/tools-home.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/mainpage.pl 3. click on "Catalogue | Upload cover images" [Sat Jun 03 21:01:28.805071 2017] [cgi:error] [pid 3554] [client 192.168.0.12:54238] AH01215: [Sat Jun 3 21:01:28 2017] upload-cover-image.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/tools/upload-cover-image.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/tools-home.pl [Sat Jun 03 21:01:28.812621 2017] [cgi:error] [pid 3554] [client 192.168.0.12:54238] AH01215: [Sat Jun 3 21:01:28 2017] upload-cover-image.pl: DBD::mysql::st execute failed: MySQL server has gone away [ for Statement " SELECT `me`.`borrowernumber`, `me`.`cardnumber`, `me`.`surname`, `me`.`firstname`, `me`.`title`, `me`.`othernames`, `me`.`initials`, `me`.`streetnumber`, `me`.`streettype`, `me`.`address`, `me`.`address2`, `me`.`city`, `me`.`state`, `me`.`zipcode`, `me`.`country`, `me`.`email`, `me`.`phone`, `me`.`mobile`, `me`.`fax`, `me`.`emailpro`, `me`.`phonepro`, `me`.`B_streetnumber`, `me`.`B_streettype`, `me`.`B_address`, `me`.`B_address2`, `me`.`B_city`, `me`.`B_state`, `me`.`B_zipcode`, `me`.`B_country`, `me`.`B_email`, `me`.`B_phone`, `me`.`dateofbirth`, `me`.`branchcode`, `me`.`categorycode`, `me`.`dateenrolled`, `me`.`dateexpiry`, `me`.`gonenoaddress`, `me`.`lost`, `me`.`debarred`, `me`.`debarredcomment`, `me`.`contactname`, `me`.`contactfirstname`, `me`.`contacttitle`, `me`.`guarantorid`, `me`.`borrowernotes`, `me`.`relationship`, `me`.`sex`, `me`.`password`, `me`.`flags`, `me`.`userid`, `me`.`opacnote`, `me`.`contactnote`, `me`.`sort1`, `me`.`sort2`, `me`.`altcontactfirstname`, `me`.`altcontactsurname`, `me`.`altcontactaddress1`, `me`.`altcontactaddress2`, `me`.`altcontactaddress3`, `me`.`altcontactstate`, `me`.`altcontactzipcode`, `me`.`altcontactcountry`, `me`.`altcontactphone`, `me`.`smsalertnumber`, `me`.`sms_provider_id`, `me`.`privacy`, `me`.`privacy_guarantor_checkouts`, `me`.`checkprevcheckout`, `me`.`updated_on`, `me`.`lastseen` FROM `borrowers` `me` WHERE ( `me`.`userid` = ? ) " with ParamValues: 0="krieg" ] at /usr/share/perl5/vendor_perl/DBIx/Class/Storage/DBI.pm line 1836.: /var/www/koha/intranet/cgi-bin/tools/upload-cover-image.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/tools-home.pl [Sat Jun 03 21:01:29.237716 2017] [cgi:error] [pid 3554] [client 192.168.0.12:54238] AH01215: [Sat Jun 3 21:01:29 2017] upload-cover-image.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/tools/upload-cover-image.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/tools-home.pl [Sat Jun 03 21:01:29.240255 2017] [cgi:error] [pid 3554] [client 192.168.0.12:54238] AH01215: [Sat Jun 3 21:01:29 2017] upload-cover-image.pl: DBD::mysql::st execute failed: MySQL server has gone away [ for Statement " SELECT `me`.`variable`, `me`.`value`, `me`.`options`, `me`.`explanation`, `me`.`type` FROM `systempreferences` `me` WHERE ( `me`.`variable` = ? ) " with ParamValues: 0="dateformat" ] at /usr/share/perl5/vendor_perl/DBIx/Class/Storage/DBI.pm line 1836.: /var/www/koha/intranet/cgi-bin/tools/upload-cover-image.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/tools-home.pl 4. click on "upload file" [Sat Jun 03 21:08:00.876394 2017] [cgi:error] [pid 3550] [client 192.168.0.12:54244] AH01215: [Sat Jun 3 21:08:00 2017] upload-file.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/tools/upload-file.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/upload-cover-image.pl [Sat Jun 03 21:08:00.940582 2017] [cgi:error] [pid 3550] [client 192.168.0.12:54244] AH01215: [Sat Jun 3 21:08:00 2017] upload-file.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/tools/upload-file.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/upload-cover-image.pl 5. click on "process images" [Sat Jun 03 21:10:45.838351 2017] [cgi:error] [pid 3531] [client 192.168.0.12:54260] AH01215: [Sat Jun 3 21:10:45 2017] upload-cover-image.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/tools/upload-cover-image.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/upload-cover-image.pl [Sat Jun 03 21:10:45.840697 2017] [cgi:error] [pid 3531] [client 192.168.0.12:54260] AH01215: [Sat Jun 3 21:10:45 2017] upload-cover-image.pl: DBD::mysql::st execute failed: MySQL server has gone away [ for Statement " SELECT `me`.`borrowernumber`, `me`.`cardnumber`, `me`.`surname`, `me`.`firstname`, `me`.`title`, `me`.`othernames`, `me`.`initials`, `me`.`streetnumber`, `me`.`streettype`, `me`.`address`, `me`.`address2`, `me`.`city`, `me`.`state`, `me`.`zipcode`, `me`.`country`, `me`.`email`, `me`.`phone`, `me`.`mobile`, `me`.`fax`, `me`.`emailpro`, `me`.`phonepro`, `me`.`B_streetnumber`, `me`.`B_streettype`, `me`.`B_address`, `me`.`B_address2`, `me`.`B_city`, `me`.`B_state`, `me`.`B_zipcode`, `me`.`B_country`, `me`.`B_email`, `me`.`B_phone`, `me`.`dateofbirth`, `me`.`branchcode`, `me`.`categorycode`, `me`.`dateenrolled`, `me`.`dateexpiry`, `me`.`gonenoaddress`, `me`.`lost`, `me`.`debarred`, `me`.`debarredcomment`, `me`.`contactname`, `me`.`contactfirstname`, `me`.`contacttitle`, `me`.`guarantorid`, `me`.`borrowernotes`, `me`.`relationship`, `me`.`sex`, `me`.`password`, `me`.`flags`, `me`.`userid`, `me`.`opacnote`, `me`.`contactnote`, `me`.`sort1`, `me`.`sort2`, `me`.`altcontactfirstname`, `me`.`altcontactsurname`, `me`.`altcontactaddress1`, `me`.`altcontactaddress2`, `me`.`altcontactaddress3`, `me`.`altcontactstate`, `me`.`altcontactzipcode`, `me`.`altcontactcountry`, `me`.`altcontactphone`, `me`.`smsalertnumber`, `me`.`sms_provider_id`, `me`.`privacy`, `me`.`privacy_guarantor_checkouts`, `me`.`checkprevcheckout`, `me`.`updated_on`, `me`.`lastseen` FROM `borrowers` `me` WHERE ( `me`.`userid` = ? ) " with ParamValues: 0="krieg" ] at /usr/share/perl5/vendor_perl/DBIx/Class/Storage/DBI.pm line 1836.: /var/www/koha/intranet/cgi-bin/tools/upload-cover-image.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/upload-cover-image.pl [Sat Jun 03 21:10:46.041433 2017] [cgi:error] [pid 3531] [client 192.168.0.12:54260] AH01215: [Sat Jun 3 21:10:46 2017] upload-cover-image.pl: DBD::mysql::db do failed: MySQL server has gone away [ for Statement " INSERT INTO sessions (id, a_session) VALUES (?, ?) ON DUPLICATE KEY UPDATE a_session = ? " ] at /usr/share/perl5/vendor_perl/CGI/Session/Driver/mysql.pm line 50.: /var/www/koha/intranet/cgi-bin/tools/upload-cover-image.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/upload-cover-image.pl [Sat Jun 03 21:10:46.042742 2017] [cgi:error] [pid 3531] [client 192.168.0.12:54260] AH01215: [Sat Jun 3 21:10:46 2017] upload-cover-image.pl: DBD::mysql::st execute failed: MySQL server has gone away [ for Statement " SELECT `me`.`variable`, `me`.`value`, `me`.`options`, `me`.`explanation`, `me`.`type` FROM `systempreferences` `me` WHERE ( `me`.`variable` = ? ) " with ParamValues: 0="dateformat" ] at /usr/share/perl5/vendor_perl/DBIx/Class/Storage/DBI.pm line 1836.: /var/www/koha/intranet/cgi-bin/tools/upload-cover-image.pl, referer: http://midgard-asenheim.fritz.box:8081/cgi-bin/koha/tools/upload-cover-image.pl