deb-systemd-invoke.

deb-systemd-invoke [OPTIONS...] ACTION [UNIT...]

--quiet
    Suppress all output

--root=PATH
    Use alternative filesystem root

ACTION
    Operation like start, stop, enable, disable, restart, status, reload, mask, unmask, preset

UNIT
    Target systemd unit file name (e.g., foo.service)

deb-systemd-invoke is a helper script in Debian systems, part of the systemd-shim or systemd-sysv packages. It enables package maintainer scripts to invoke systemd unit operations (like start, stop, enable, disable) without requiring systemd as PID 1.

The script checks if systemd is the init system (/proc/1/comm contains 'systemd'). If yes, it delegates to systemctl. Otherwise, it falls back to SysV tools like update-rc.d for boot-time enabling/disabling or invoke-rc.d for runtime control.

This ensures smooth package installation/upgrades across init systems (SysV, Upstart, OpenRC). It supports most common systemctl actions but is not a full replacement. Primarily for postinst, prerm scripts in debian/rules, avoiding direct systemctl calls that fail on non-systemd setups.

Usage prevents errors like 'Failed to connect to bus' on legacy systems, promoting init-agnostic packaging.

Warning: For maintainer scripts only; unreliable for interactive/shell use. Outputs may vary by init system. Not all systemctl features supported.

Runtime: invoke-rc.d; Boot enable/disable: update-rc.d; No-op for unsupported actions on non-systemd.

deb-systemd-invoke enable foo.service
deb-systemd-invoke --quiet start foo.service

Introduced in Debian wheezy (2013) via systemd-shim for gradual systemd adoption. Evolved in jessie (2015) with full init detection. Maintained in systemd-sysv post-jessie; usage declined as systemd became default.

systemctl(1), update-rc.d(8), invoke-rc.d(8)