nix3-store-roots-daemon(1)

    Warning
    This program is experimental and its interface is subject to change.

Name

nix store roots-daemon - run a daemon that returns garbage collector roots on request

Synopsis

nix store roots-daemon [option…]

Examples

•   Run the daemon:

    # nix store roots-daemon

Description

This command runs a daemon that serves garbage collector roots from a Unix domain socket. It is not required in all Nix installations, but is useful when the main Nix daemon is not running as root and therefore cannot find runtime roots by scanning /proc.

When the garbage collector runs with use-roots-daemon enabled, it connects to this daemon to discover additional roots that should not be collected.

The daemon listens on <state-dir>/gc-roots-socket/socket (typically /nix/var/nix/gc-roots-socket/socket).

Protocol

The protocol is simple. For each client-initiated Unix socket connection, the server:

1.  Sends zero or more store paths as NUL-terminated (\0) strings.

2.  Closes the connection.

Example (with \0 shown as newlines for clarity): /nix/store/s66mzxpvicwk07gjbjfw9izjfa797vsw-hello-2.12.1 /nix/store/fvpr7x8l3illdnziggvkhdpf6vikg65w-git-2.44.0

Security

No information is provided as to which processes are opening which store paths. While only the main Nix daemon needs to use this daemon, any user able to talk to the main Nix daemon can already obtain the same information with nix-store --gc --print-roots.

Therefore, restricting this daemon to only accept the Nix daemon as a client is, while recommended for defense-in-depth reasons, strictly speaking not reducing what information can be extracted versus merely restricting this daemon to accept connections from any allowed user.

Systemd socket activation

nix store roots-daemon supports systemd socket-based activation, just like nix daemon.

Options

  Logging-related options

•   --debug

    Set the logging verbosity level to ‘debug’.

•   --log-format format

    Set the format of log output; one of raw, internal-json, bar or bar-with-logs.

•   --print-build-logs / -L

    Print full build logs on standard error.

•   --quiet

    Decrease the logging verbosity level.

•   --verbose / -v

    Increase the logging verbosity level.

  Miscellaneous global options

•   --help

    Show usage information.

•   --offline

    Disable substituters and consider all previously downloaded files up-to-date.

•   --option name value

    Set the Nix configuration setting name to value (overriding nix.conf).

•   --refresh

    Consider all previously downloaded files out-of-date.

•   --version

    Show version information.

    Note

    See man nix.conf for overriding configuration settings with command line flags.