Hello all, According to the document, I built memcached as a back end, so I built it from the source, but the following error message is output and can not be used. https://knot-resolver.readthedocs.io/en/stable/build.html#building-from-sou… $ sudo kresd [system] interactive mode error: error loading module 'memcached' from file '/usr/local/lib/kdns_modules/memcached.so': /usr/local/lib/kdns_modules/memcached.so: undefined symbol: luaopen_memcached error: No such file or directory $ ll /usr/local/lib/kdns_modules/ total 404 drwxr-xr-x 4 root root 4096 Dec 13 21:59 ./ drwxr-xr-x 7 root root 4096 Dec 13 21:59 ../ -rwxr-xr-x 1 root root 35904 Dec 13 21:59 ahocorasick.so* -rwxr-xr-x 1 root root 38848 Dec 13 21:59 cookies.so* drwxr-xr-x 2 root root 4096 Dec 13 21:59 daf/ -rw-r--r-- 1 root root 8664 Dec 13 21:59 daf.lua -rw-r--r-- 1 root root 1098 Dec 13 21:59 detect_time_jump.lua -rw-r--r-- 1 root root 2329 Dec 13 21:59 detect_time_skew.lua -rw-r--r-- 1 root root 2218 Dec 13 21:59 dns64.lua -rwxr-xr-x 1 root root 45016 Dec 13 21:59 dnstap.so* -rw-r--r-- 1 root root 1204 Dec 13 21:59 etcd.lua -rw-r--r-- 1 root root 3199 Dec 13 21:59 graphite.lua -rwxr-xr-x 1 root root 44376 Dec 13 21:59 hints.so* drwxr-xr-x 2 root root 4096 Dec 13 21:59 http/ -rw-r--r-- 1 root root 11077 Dec 13 21:59 http.lua -rw-r--r-- 1 root root 1263 Dec 2 00:16 ketcd.lua -rw-r--r-- 1 root root 7967 Dec 13 21:59 kres-gen.lua -rw-r--r-- 1 root root 10178 Dec 13 21:59 kres.lua -rwxr-xr-x 1 root root 14216 Dec 13 21:59 memcached.so* -rw-r--r-- 1 root root 15867 Dec 13 21:59 policy.lua -rw-r--r-- 1 root root 5346 Dec 13 21:59 predict.lua -rw-r--r-- 1 root root 4267 Dec 13 21:59 priming.lua -rw-r--r-- 1 root root 4313 Dec 13 21:59 prometheus.lua -rwxr-xr-x 1 root root 18336 Dec 13 21:59 redis.so* -rw-r--r-- 1 root root 3639 Dec 13 21:59 renumber.lua -rwxr-xr-x 1 root root 34048 Dec 13 21:59 stats.so* -rw-r--r-- 1 root root 1818 Dec 13 21:59 ta_signal_query.lua -rw-r--r-- 1 root root 15314 Dec 13 21:59 trust_anchors.lua -rw-r--r-- 1 root root 2068 Dec 13 21:59 version.lua -rw-r--r-- 1 root root 2656 Dec 13 21:59 view.lua -rw-r--r-- 1 root root 1658 Dec 13 21:59 workarounds.lua -rw-r--r-- 1 root root 5307 Dec 13 21:59 zonefile.lua Is it something you need to do with a description other than documentation? The source file is working with knot-resolver-1.5.1. env: $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.04.3 LTS Release: 16.04 Codename: xenial $ sudo make info PREFIX="/usr/local" ETCDIR="/etc/knot-resolver/" CFLAGS="-fstack-protector" fatal: Not a git repository (or any of the parent directories): .git Target: Knot DNS Resolver 1.5.1-POSIX Compiler: cc -fstack-protector -std=c99 -D_GNU_SOURCE -Wno-unused -Wtype-limits -Wformat -Wformat-security -Wall -I/home/kometch/knot-resolver-1.5.1 -I/home/kometch/knot-resolver-1.5.1/lib/generic -I/home/kometch/knot-resolver-1.5.1/contrib -I/home/kometch/knot-resolver-1.5.1/contrib/lmdb -DPACKAGE_VERSION="\"1.5.1\"" -DPREFIX="\"/usr/local\"" -DMODULEDIR="\"/usr/local/lib/kdns_modules\"" -O2 -D_FORTIFY_SOURCE=2 -I/usr/include/p11-kit-1 -I/usr/include/luajit-2.1 -I/usr/include/p11-kit-1 -Icontrib/ccan/compiler -Icontrib/ccan/ilog -Icontrib/ccan/isaac -Icontrib/ccan/json -Icontrib/ccan/asprintf -Icontrib/murmurhash3 -DENABLE_COOKIES Variables --------- HARDENING: yes BUILDMODE: dynamic PREFIX: /usr/local PREFIX: /usr/local DESTDIR: BINDIR: /usr/local/bin SBINDIR: /usr/local/sbin LIBDIR: /usr/local/lib ETCDIR: /etc/knot-resolver/ INCLUDEDIR: /usr/local/include MODULEDIR: /usr/local/lib/kdns_modules Core Dependencies ------------ [yes] libknot (lib) [yes] embedded lmdb (lib) [yes] luajit (daemon) [yes] libuv (daemon) [yes] libgnutls (daemon) Optional -------- [no] doxygen (doc) [no] sphinx-build (doc) [no] python-breathe (doc) [yes] go (modules/go, Go buildmode=c-shared support) [yes] libmemcached (modules/memcached) [yes] hiredis (modules/redis) [yes] cmocka (tests/unit) [yes] systemd (daemon) [yes] nettle (modules/cookies) [yes] Lua socket ltn12 (trust anchor bootstrapping) [yes] Lua ssl.https (trust anchor bootstrapping) [yes] libedit (client) [yes] libfstrm (modules/dnstap) [yes] libprotobuf-c (modules/dnstap) [yes] proto-c (modules/dnstap) [yes] lcov (code coverage) [yes] luacov (code coverage) make: Nothing to be done for 'info'. ii libmemcached-dev 1.0.18-4.1 arm64 C and C++ client library to the memcached server (development files) ii libmemcached-tools 1.0.18-4.1 arm64 Commandline tools for talking to memcached via libmemcached ii libmemcached11:arm64 1.0.18-4.1 arm64 C and C++ client library to the memcached server ii libmemcachedutil2:arm64 1.0.18-4.1 arm64 library implementing connection pooling for libmemcached $ sudo memcached -V memcached 1.5.3 Best regards.