Apps

ClickHouse ships as a single multi-call binary: clickhouse. Symlinks like clickhouse-server, clickhouse-client, clickhouse-local are dispatched via argv[0]. The dispatch table is in programs/main.cpp.

The directories under programs/ hold the per-app code; the heavy lifting happens in src/ (see Systems).

Catalog

Subcommand	Source	Purpose
server	programs/server/	The long-running database server. See Server.
client	programs/client/	Interactive native-protocol terminal. See Client.
local	programs/local/	Embedded engine running queries against local files. See Local.
keeper	programs/keeper/	Native Raft-based coordination service. See Keeper.
keeper-client	programs/keeper-client/	Interactive client for clickhouse-keeper.
keeper-converter	programs/keeper-converter/	Migrates ZooKeeper snapshots into Keeper format.
keeper-bench	programs/keeper-bench/	Coordination throughput benchmark.
keeper-data-dumper	programs/keeper-data-dumper/	Dumps Keeper Raft logs/snapshots for forensics.
keeper-utils	programs/keeper-utils/	Misc Keeper-side utilities.
benchmark	programs/benchmark/	Concurrency benchmark issuing parallel queries.
compressor	programs/compressor/	Compress/decompress files using ClickHouse codecs.
format	programs/format/	Pretty-prints/normalizes a SQL query through the parser.
obfuscator	programs/obfuscator/	Anonymises a dataset while preserving statistical properties (used for sharing reproducers).
disks	programs/disks/	A REPL/CLI for inspecting and manipulating any configured IDisk.
git-import	programs/git-import/	Imports a git repo's commits/files into ClickHouse for analysis.
static-files-disk-uploader	programs/static-files-disk-uploader/	Bulk-uploads files into an object-storage disk.
extract-from-config	programs/extract-from-config/	Reads a single value out of config.xml (used by init scripts).
su	programs/su/	A small su clone used by the official Docker entry point.
docker-init	programs/docker-init/	The official Docker entry point.
install / start / stop / status / restart	programs/install/	Self-installation onto a host (legacy, single-binary deploys).
check-marks	programs/check-marks/	Verifies *.mrk* mark file consistency.
checksum-for-compressed-block	programs/checksum-for-compressed-block/	Recomputes a checksum for a compressed block (forensics).
zookeeper-dump-tree / zookeeper-remove-by-list	programs/zookeeper-*/	One-off ZooKeeper maintenance tools.
hash-binary	inline in main.cpp	Prints getHashOfLoadedBinaryHex() for tamper detection.
self-extracting	programs/self-extracting/	Build helper for the self-extracting installer.
bash-completion	programs/bash-completion/	Bash/zsh completion script.

Dispatch

clickhouse foo runs the foo entry point. So does:

• A symlink named clickhouse-foo.
• A flag --foo as the first argument (clickhouse --client ...).
• For convenience, when you run a bare clickhouse binary on a script-like argument, it routes to local (so clickhouse my_query.sql is clickhouse-local my_query.sql).
• If the argument list contains --host or --port, it routes to client.

The relevant logic is isClickhouseApp() in programs/main.cpp.

Hardening done in main.cpp

• dlopen/dlclose/dlerror are overridden to do nothing — the binary refuses to load arbitrary shared libraries (see the comment "We absolutely discourage the ancient technique of loading 3rd-party uncontrolled dangerous libraries...").
• Sanitizer defaults are baked in (e.g. halt_on_error=1 for ASan/TSan, print_stacktrace=1 for UBSan, ignored OpenSSL leak suppressions).
• updatePHDRCache() is called early so signal handlers can produce reliable stack traces.
• OpenSSLInitializer::instance() is invoked from a constructor with priority 202 to guarantee correct ordering.
• Jemalloc default messages are silenced in release.

Where to read next

• Server — the production ClickHouse server.
• Client — the interactive native-TCP terminal.
• Local — the same engine without a server process.
• Keeper — the native ZooKeeper-compatible coordinator.
• Utilities — compressor, format, obfuscator, disks, etc.