Hi I am building "seL4test" using the Docker image on Ubuntu 18.04.3 LTS, a 64-bit system. After entering "../init-build.sh -DPLATFORM=x86_64 -DSIMULATION=TRUE" in a build directory within Docker it complained "Could NOT find NANOPB (missing: PROTOBUF_PROTOC_EXECUTABLE)". I wonder should I manually download and install protocol buffer compiler, protoc? Please advise. Thank for your help. Jacob =============================================== loading initial cache file /host/projects/sel4test/settings.cmake correct_platform_strings: Attempting to correct PLATFORM: x86_64 to new valid KernelPlatform: pc99 KernelSel4Arch: x86_64 -- Found seL4: /host/kernel -- The C compiler identification is GNU 6.5.0 -- The CXX compiler identification is GNU 6.5.0 -- The ASM compiler identification is GNU -- Found assembler: /usr/bin/gcc -- Check for working C compiler: /usr/bin/gcc -- Check for working C compiler: /usr/bin/gcc -- works -- Detecting C compiler ABI info -- Detecting C compiler ABI info - done -- Detecting C compile features -- Detecting C compile features - done -- Check for working CXX compiler: /usr/bin/g++ -- Check for working CXX compiler: /usr/bin/g++ -- works -- Detecting CXX compiler ABI info -- Detecting CXX compiler ABI info - done -- Detecting CXX compile features -- Detecting CXX compile features - done -- Found elfloader-tool: /host/tools/seL4/elfloader-tool -- Found musllibc: /host/projects/musllibc -- Found util_libs: /host/projects/util_libs -- Found seL4_libs: /host/projects/seL4_libs -- Found sel4_projects_libs: /host/projects/sel4_projects_libs -- Found sel4runtime: /host/projects/sel4runtime -- Performing Test compiler_arch_test -- Performing Test compiler_arch_test - Success -- Found PythonInterp: /usr/bin/python (found version "2.7.15") -- Could NOT find NANOPB (missing: PROTOBUF_PROTOC_EXECUTABLE) -- CPIO test cpio_reproducible_flag PASSED -- Configuring done -- Generating done -- Build files have been written to: /host/build-x86