Upstart
 | |
| Original author(s) | Scott James Remnant |
|---|---|
| Developer(s) | Canonical Ltd. |
| Initial release | August 24, 2006 |
| Stable release | 1.11 / November 14, 2013 |
| Written in | C |
| Operating system | Linux |
| Type | Init daemon |
| License | GPLv2 |
| Website | upstart.ubuntu.com |
Upstart is an event-based replacement for the traditional init daemon — the method by which several Unix-like computer operating systems perform tasks when the computer is started. It was written by Scott James Remnant, a former employee of Canonical Ltd.
Rationale
The traditional init process was originally only responsible for bringing the computer into a normal running state after power-on, or gracefully shutting down services prior to shutdown. As a result, the design is strictly synchronous, blocking future tasks until the current one has completed. Its tasks must also be defined in advance, as they are limited to this prep or cleanup function. This leaves it unable to handle various non-startup-tasks on a modern desktop computer elegantly, including:
- The addition or removal of USB pen drives and other portable storage / network devices while the machine is running
- The discovery and scanning of new storage devices, without locking the system, especially when a disk may not even power on until it is scanned
- The loading of firmware for a device, which may need to occur after it is detected but before it is usable
Upstart's event-driven model allows it to respond to events asynchronously as they are generated.[1]
Design
Upstart operates asynchronously — as well as handling the starting of tasks and services during boot and stopping them during shutdown, it supervises them while the system is running.
Easy transition and perfect backwards compatibility with sysvinit were explicit design goals.[2] As such, Upstart is able to run sysvinit scripts unmodified. In this way it differs from most other init replacements (besides systemd and OpenRC), which usually assume and require complete transition to run properly, and don't support a mixed environment of traditional and new startup methods.[3]
Upstart allows for extensions to its event model through the use of initctl to input custom, single events, or event bridges to integrate many or more complicated events.[4] By default, Upstart includes bridges for: socket, dbus, udev, file, and dconf events, but more (e.g. a Mach ports bridge, or a devd (found on FreeBSD systems) bridge) are possible.[5]
Adoption
As Upstart matures, it is intended that its role will expand to the duties currently handled by cron, anacron, the at command's daemon (atd), and possibly (but much less likely) inetd.
Distributions in which Upstart is enabled by default:
- Upstart was first included in Ubuntu in the 6.10 (Edgy Eft) release in late 2006, replacing sysvinit. Ubuntu 9.10 (Karmic Koala) introduced native Upstart bootup as of Alpha 6.[6]
- Upstart replaced the sysvinit in Maemo 5 for Nokia Internet tablets.[7]
- Upstart is used in HP's webOS for the Palm Pre, Palm Pixi (both before Palm was bought out by HP), HP Veer, and HP Pre 3 smart phones, along with the HP TouchPad tablet.[8]
- Upstart is used in Google's Chrome OS.[9]
Distributions that used Upstart in some versions but moved to systemd in later versions:
- Upstart replaced sysvinit in Fedora 9, and functioned in the same manner as it did in Ubuntu, i.e. it replaces sysvinit, while retaining the existing scripts. However, Upstart has been replaced by systemd in Fedora 15 release.[10][11]
- Red Hat includes Upstart in their Red Hat Enterprise Linux 6 release.[12] As a result, it is also used by RHEL 6 variants such as CentOS, Scientific Linux, and Oracle Linux.
Other:
- Debian considered switching for the squeeze release,[13] and is discussing it again for the jessie release.[14]
- openSUSE included upstart in version 11.3 Milestone 4, but not as default.[15] systemd replaced Upstart, as the default init system in openSUSE 12.1.[16]
See also
References
- ↑ Remnant, Scott James (2006-08-26). "Upstart in Universe". Netsplit. Retrieved 2009-09-12.
- ↑ "Upstart", Launch Pad (605007), Ubuntu.
- ↑ "Discussion of design and implementation of Upstart", Ubuntu Wiki, Canonical.
- ↑ "initctl emit". The Upstart Cookbook. Canonical. Retrieved 26 January 2014.
- ↑ "Bridges". The Upstart Cookbook. Canonical. Retrieved 26 January 2014.
- ↑ "Upstart", About (Ubuntu)
- ↑ Fremantle, Maemo, retrieved 2009-08-24
- ↑ Palm Pre, Live Journal, retrieved 2009-07-09
- ↑ Software Architecture: Chromium OS design documents, Google, retrieved 25 January 2014
- ↑ Fedora 14 Accepted Features, 2010-07-13, retrieved 2010-07-13
- ↑ "Fedora defers systemd to F15". Linux Weekly News. 2010-09-14. Retrieved 2010-09-17.
- ↑ "Deployment". Red Hat Enterprise Linux 6: Technical Notes. Red Hat. Retrieved 2013-12-31.
- ↑ Petter Reinholdtsen (2009-09-05), The future of the boot system in Debian, Debian, retrieved 2009-10-12
- ↑ Marco d'Itri (2013-10-25), Proposal: switch init system to systemd or upstart, Debian, retrieved 2013-10-29
- ↑ OpenSUSE gets an Upstart, The H, 2010-03-26, archived from the original on 8 December 2013, retrieved 2010-04-04
- ↑ Chris von Eitzen (2011-11-16), openSUSE 12.1 arrives with systemd and Btrfs, The H, archived from the original on 20 April 2012, retrieved 2011-11-16
External links
- Home page
- Upstart on Launchpad
- Upstart Cookbook
- Upstart Cookbook
- Init systems comparison: part 1 and part 2 (LWN.net)
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