// Copyright (C) 2016-2017 Luke Shumaker <lukeshu@sbcglobal.net>
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package sd_login introspects session and login information from
// systemd, logind, and machined.
//
// There are 5 basic object types that these three system services
// manage and are introspected by this package.
//
// The machine manager maintains a list of "machines":
//
//  1. machine: A local container or virtual machine
//
// The host system, and machines hosted on it, may each run their own
// login manager, which keeps track of "seats", "sessions", and
// "users":
//
//  2. seat: A set of hardware devices for a workspace; i.e. a screen
//     and keyboard
//
//  3. session: A login session; tied to 0 or 1 seats (0 for things
//     like SSH login)
//
//  4. user: Keeps track of logged in users; that is, users with 1 or
//     more sessions
//
// Finally, sessions and users can be used to group together
// "processes", which are kept track of by cgroup manager:
//
//  5. process: A process may belong to a session, or directly to a
//     user if it is not part of a session.  This "belonging" is
//     separate accounting by the cgroup manager; it is NOT the same
//     as the EUID/RUID.
package sd_login