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How to Build, Run and Debug ClickHouse on Linux for s390x (zLinux)

At the time of writing (2024 May), support for the s390x platform is considered experimental, i.e. some features are disabled or broken on s390x.

Building ClickHouse for s390x

s390x has two OpenSSL-related build options:

  • By default, OpenSSL is build on s390x as a shared library. This is different from all other platforms, where OpenSSL is build as static library.
  • To build OpenSSL as a static library regardless, pass -DENABLE_OPENSSL_DYNAMIC=0 to CMake.

These instructions assume that the host machine is x86_64 and has all the tooling required to build natively based on the build instructions. It also assumes that the host is Ubuntu 22.04 but the following instructions should also work on Ubuntu 20.04.

In addition to installing the tooling used to build natively, the following additional packages need to be installed:

apt-get install binutils-s390x-linux-gnu libc6-dev-s390x-cross gcc-s390x-linux-gnu binfmt-support qemu-user-static

If you wish to cross compile rust code install the rust cross compile target for s390x:

rustup target add s390x-unknown-linux-gnu

The s390x build uses the mold linker, download it from and place it into your $PATH.

To build for s390x:

cmake -DCMAKE_TOOLCHAIN_FILE=cmake/linux/toolchain-s390x.cmake ..


Once built, the binary can be run with, e.g.:

qemu-s390x-static -L /usr/s390x-linux-gnu ./clickhouse


Install LLDB:

apt-get install lldb-15

To Debug a s390x executable, run clickhouse using QEMU in debug mode:

qemu-s390x-static -g 31338 -L /usr/s390x-linux-gnu ./clickhouse

In another shell run LLDB and attach, replace <Clickhouse Parent Directory> and <build directory> with the values corresponding to your environment.

(lldb) target create ./clickhouse
Current executable set to '/<Clickhouse Parent Directory>/ClickHouse/<build directory>/programs/clickhouse' (s390x).
(lldb) settings set target.source-map <build directory> /<Clickhouse Parent Directory>/ClickHouse
(lldb) gdb-remote 31338
Process 1 stopped
* thread #1, stop reason = signal SIGTRAP
frame #0: 0x0000004020e74cd0
-> 0x4020e74cd0: lgr %r2, %r15
0x4020e74cd4: aghi %r15, -160
0x4020e74cd8: xc 0(8,%r15), 0(%r15)
0x4020e74cde: brasl %r14, 275429939040
(lldb) b main
Breakpoint 1: 9 locations.
(lldb) c
Process 1 resuming
Process 1 stopped
* thread #1, stop reason = breakpoint 1.1
frame #0: 0x0000004005cd9fc0 clickhouse`main(argc_=1, argv_=0x0000004020e594a8) at main.cpp:450:17
447 #if !defined(FUZZING_MODE)
448 int main(int argc_, char ** argv_)
449 {
-> 450 inside_main = true;
451 SCOPE_EXIT({ inside_main = false; });
453 /// PHDR cache is required for query profiler to work reliably

Visual Studio Code integration

  • CodeLLDB extension is required for visual debugging.
  • Command Variable extension can help dynamic launches if using CMake Variants.
  • Make sure to set the backend to your LLVM installation eg. "lldb.library": "/usr/lib/x86_64-linux-gnu/"
  • Make sure to run the clickhouse executable in debug mode prior to launch. (It is also possible to create a preLaunchTask that automates this)

Example configurations


default: relwithdebinfo
short: Debug
long: Emit debug information
buildType: Debug
short: Release
long: Optimize generated code
buildType: Release
short: RelWithDebInfo
long: Release with Debug Info
buildType: RelWithDebInfo
short: MinSizeRel
long: Minimum Size Release
buildType: MinSizeRel

default: default
description: Select toolchain
short: x86_64
long: x86_64
short: s390x
long: s390x
CMAKE_TOOLCHAIN_FILE: cmake/linux/toolchain-s390x.cmake


"version": "0.2.0",
"configurations": [
"type": "lldb",
"request": "custom",
"name": "(lldb) Launch s390x with qemu",
"targetCreateCommands": ["target create ${command:cmake.launchTargetPath}"],
"processCreateCommands": ["gdb-remote 2159"],
"preLaunchTask": "Run ClickHouse"


This would also put different builds under different subfolders of the build folder.

"cmake.buildDirectory": "${workspaceFolder}/build/${buildKitVendor}-${buildKitVersion}-${variant:toolchain}-${variant:buildType}",
"lldb.library": "/usr/lib/x86_64-linux-gnu/"

#! /bin/sh
echo 'Starting debugger session'
cd $1
qemu-s390x-static -g 2159 -L /usr/s390x-linux-gnu $2 $3 $4


Defines a task to run the compiled executable in server mode under a tmp folder next to the binaries, with configuration from under programs/server/config.xml.

"version": "2.0.0",
"tasks": [
"label": "Run ClickHouse",
"type": "shell",
"isBackground": true,
"command": "${workspaceFolder}/.vscode/",
"args": [
"problemMatcher": [
"pattern": [
"regexp": ".",
"file": 1,
"location": 2,
"message": 3
"background": {
"activeOnStart": true,
"beginsPattern": "^Starting debugger session",
"endsPattern": ".*"