Hello Oleg, The Ubuntu package uses GnuTLS and therefore your olcTLSCipherSuite setting needs to contain a valid GnuTLS priority string.
https://gnutls.org/manual/html_node/Priority-Strings.html The slapd crash you are seeing is an Ubuntu-specific bug and has been fixed in later versions. https://bugs.launchpad.net/bugs/1103353 If you configure a valid GnuTLS priority string, it will not crash. In future please report issues with distro packages to the distro's bug tracker (in this case Launchpad); we can always forward them here if appropriate. This ITS will be closed.
