Upstart

Upstart is an open source drop-in replacement for the well known, yet deprecated initd (also known as System V init or /sbin/init daemon) software designed to start certains services and tasks during the boot process of a Linux operating system, administering them while the OS is in use, as well as to stop them during shutdown.

It's easily deployable in Linux distributions

The main difference between the init daemon and Upstart, is that the latter uses events to handle specific services during system startup and shutdown. It was mainly designed for and used in the Ubuntu Linux operating system.

However, the project is developed in such a way that it can be easily deployed and integrated in any other Linux distribution, as a replacement for System-V init. The sad part of this project is that it was only used in Ubuntu (and its derivatives) and Fedora, as other Linux distros switched to the more complex and modern systemd software.

Handles services and tasks

As mentioned, Upstart can handle both services and tasks during boot or shutdown processes based on events, which can be generated as either services or tasks. In addition, it can respawn dead services, communicate with the init daemon via the D-Bus service, and handle user services.

It can receive events from any other process, respawn and supervise init daemons that are separated from their parent process, and allows users to stop or start their own user services.

Availability and supported OSes

The project is distributed only as a source archive, which can be configured, compiled and installed in any Linux operating system. However, the developers recommend users to use the official Upstart packages from the default software repositories of their Linux distribution.

Apparently, systemd has received so much attention from Linux OS developers that even Ubuntu will switch to it, and that says a lot about the future of the Upstart project.

What is new in this release:

• Enforce 'initctl set-env' from being called from system job (LP: #1356824).
• Defer use of remove-on-empty to stop session-level cgroup jobs from racing with cgmanager which can remove the cgroup before subsequent job processes have been moved into them (LP: #1357252).

What is new in version 1.13.1:

• Fix for Session Init crasher triggered by restarting a job that runs 'initctl unset-env' (LP: #1222705).

What is new in version 1.13:

• Fix for handling upgrade from non-stateful-re-exec instance to a stateful-re-exec-capable one (LP:#1303891).
• Disable chroot sessions by default. A new '--chroot-sessions' command-line option restores the old default behaviour.
• New tests and improved documentation.
• Fix for Session Init umask change on re-exec (LP: #1302117).
• Allow '--confdir' to look for system jobs in multiple locations, which also adds new command-line options '--append-confdir' and '--prepend-confdir' for full flexibility (LP: #1315060).
• Allow initctl(8) commands 'set-env' and 'unset-env' to operate on multiple environment variables (LP: #1324096).
• Support for cgroups via a new 'cgroup' stanza. This makes use of cgmanager(8) and is available to both System and Session Inits.
• Support for cgroups can be disabled at built-time if required. See init(5) for 'cgroup' stanza syntax and examples.

What is new in version 1.12.1:

• Fixed re-exec breakage caused by incorrect D-Bus API usage.
• Tests updated to catch this issue.

What is new in version 1.12:

• Stop Upstart indirectly stealing console ownership (most noticeably when run in a container).
• Fixed bug that could result in incorrect output from initctl(8) environment commands.
• Fixed incorrect variable usage which could result in a crash (LP: #1222705).
• Fixed stateful re-exec issue triggered by invalid jobs (LP: #1269731).
• Stateful re-exec fix to serialise the D-Bus session bus (LP: #1258098).
• init-checkconf(8) now uses a Session Init and can also now be run as root.
• upstart-socket-bridge(8) now supports IPv6 (thanks to Kai Mast and Cameron Norman).
• Allow telinit(8) to work on systems with no D-Bus system bus.
• Numerous test improvements.
• Lots of man-page improvements.

What is new in version 1.11:

• Add '--no-dbus' command-line option for the init(8) daemon (allowing event propagation to the Session Init via the upstart-event-bridge(8) to be disabled).
• Serialise Session Init job environment table on re-exec (LP: #1238078).
• upstart-{dbus,socket}-bridge(8): Don't clobber existing PATH (LP: #1234898).
• upstart-file-bridge(8):
• Allow watching for directory creation (LP: #1221466).
• Reduce default output.
• upstart-local-bridge(8): Handle arbitrary numbers of pairs and additional checks on input validity (LP: #1234898).
• Improved Session Init shutdown speed (LP: #1227212).
• New configure options: '--disable-local-bridge', '--disable-socket-bridge'.
• Added upstart-file-bridge(8) and Session Init re-exec integration tests.
• Retain umask for Session Init (LP: #1240686).
• Make Session Init connect to D-Bus Session Bus on request (LP: #1203595, #1235649)
• Improved build-time ABI compliance checking.
• Doc updates and lots of test refinements.

What is new in version 1.10:

• upstart-local-bridge: New bridge for starting jobs on local socket connections.
• upstart-dconf-bridge: New bridge for Session Inits.
• upstart-dbus-bridge: New '--bus-name' option to allow bus name variable to be included in dbus-event(7).
• New "reload signal" stanza to allow jobs to specify a custom signal that will be sent to the main process (rather than the default SIGHUP).
• Inclusion of Session Init sample jobs.
• Re-exec fixes for handling chroot sessions.
• Shutdown fix for Session Inits.
• New python3 module and accompanying integration test suite for testing Upstart running as PID 1 and as a Session Init (priveleged and non-privileged).

What is new in version 1.9.1:

• Fix respawn behaviour regression (introduced in version 1.8) affecting jobs which also specify shell meta-characters in the exec stanza (LP: #1181789).
• Fix common bug which could cause a bridge to crash (LP: #1197225).
• Various fixes for libupstart.
• initctl2dot: Layout improvements.

What is new in version 1.9:

• Apparmor support added by means of two new stanzas: 'apparmor load' and 'apparmor switch' (thanks Marc Deslauriers).
• Stateful re-exec: now serialises all objects, not just the minimum set.
• Allow inherited environment variables to be unset for Session Inits.
• Ability to specify multiple configuration directories when running as a Session Init.
• libupstart: Client library for communicating with Upstart.
• upstart-dbus-bridge: New bridge to allow jobs to react to D-Bus signals.
• The usual round of fixes and doc improvements.