Kernel limits the installer sets and persists.
ClickHouse needs raised kernel limits. The installer applies and persists them so they survive reboots:
sysctl -w vm.max_map_count=262144 # /etc/sysctl.d/99-d0pe-clickhouse.conf vm.max_map_count = 262144 # /etc/security/limits.d/99-d0pe.conf * soft nofile 262144 * hard nofile 262144
The ClickHouse compose service also sets ulimits.nofile: 262144, so the container matches the host. You don't run these by hand — the installer does. This page is here so you know what changed.