The document discusses systemd, a new init system for Linux that aims to make booting faster by starting processes in parallel and starting fewer processes. It does this by setting up sockets in parallel and starting daemons on demand when sockets are opened. This approach is inspired by xinetd and is also used by other operating systems like Mac OS X. Systemd provides features like managing processes, units to configure services and sockets, and is coming to major Linux distributions. Daemons will need to adapt by avoiding things like forking and writing PID files.

1. systemd

5. How?

9. It reads /etc/inittab to find the default run level (initdefault) [root@tachyon ~]# grep initdefault /etc/inittab id:5:initdefault:

11. It reads /etc/inittab to find the default run level (initdefault)

12. It then reads the files starting with S in /etc/rc.d/rc${initdefault}.d [root@tachyon ~]# ls -1 /etc/rc.d/rc5.d/S* /etc/rc.d/rc5.d/S02lvm2-monitor /etc/rc.d/rc5.d/S08ip6tables /etc/rc.d/rc5.d/S08iptables /etc/rc.d/rc5.d/S11auditd /etc/rc.d/rc5.d/S11portreserve ...

14. It reads /etc/inittab to find the default run level (initdefault)

15. It then reads the files starting with S in /etc/rc.d/rc${initdefault}.d

16. It executes each one in order, one at a time.

18. Do it in parallel?

24. upstart then resolves these dependencies and starts up as many things as it can in parallel

40. Then we catch the request and start the daemon.

49. When a connection is made, start the related daemon

54. Hand socket to daemon – 'wait' option

58. /var/run/dbus/system_bus_socket

60. /var/run/dbus/system_bus_socket

61. /var/run/rpcbind.sock

63. /var/run/dbus/system_bus_socket

64. /var/run/rpcbind.sock

65. /dev/log

68. Set them all up in parallel

70. Set them all up in parallel

71. When the socket is opened, start up its related daemon

73. Set them all up in parallel

74. When the socket is opened, start up its related daemon and hand the socket to it

76. Set them all up in parallel

79. Set them all up in parallel

81. Only for that request

83. Set them all up in parallel

84. When the socket is opened, start up its related daemon and hand the socket to it

85. Same logic for D-Bus

87. Set them all up in parallel

88. When the socket is opened, start up its related daemon and hand the socket to it

89. Same logic for D-Bus

90. Same logic for filesystems

92. Set them all up in parallel

93. When the socket is opened, start up its related daemon and hand the socket to it

94. Same logic for D-Bus

99. xinetd!

103. Start fewer processes

113. awk: 92 times

117. Then they go off and do what they like

121. shutdown

123. shutdown

124. log on failure

126. shutdown

127. log on failure

128. maintain their resources

130. shutdown

131. log on failure

136. Info via /proc/$$/cgroup

138. Info via /proc/$$/cgroup

139. Notify when cgroup is empty

141. Info via /proc/$$/cgroup

142. Notify when cgroup is empty

143. Resource limits for entire group

147. Socket – unix, internet, fifo

149. Socket – unix, internet, fifo

150. Device – from udev

152. Socket – unix, internet, fifo

153. Device – from udev

154. Mount – standard filesystem mount

156. Socket – unix, internet, fifo

157. Device – from udev

158. Mount – standard filesystem mount

159. Automount – paired with mount

161. Socket – unix, internet, fifo

162. Device – from udev

163. Mount – standard filesystem mount

164. Automount – paired with mount

165. Target – logical group of units

167. Socket – unix, internet, fifo

168. Device – from udev

169. Mount – standard filesystem mount

170. Automount – paired with mount

171. Target – logical group of units

172. Snapshot – save and restore state

174. Socket

175. Device

176. Mount

177. Automount

178. Target

179. Snapshot

181. Socket

182. Device

183. Mount

184. Automount

185. Target

186. Snapshot

188. Socket

189. Device

190. Mount

191. Automount

192. Target

193. Snapshot

195. Socket – cups.socket

196. Device

197. Mount

198. Automount

199. Target

200. Snapshot

202. Socket – cups.socket

203. Device – udev

204. Mount

205. Automount

206. Target

207. Snapshot

209. Socket – cups.socket

210. Device – udev

211. Mount – /etc/fstab

212. Automount

213. Target

214. Snapshot

216. Socket – cups.socket

217. Device – udev

218. Mount – /etc/fstab

219. Automount – home.automount

220. Target – multi-user.target

221. Snapshot – suspend.snapshot

224. Fully compatible with System V init scripts

226. Fully compatible with System V init scripts, /etc/fstab and other files

228. Fully compatible with System V init scripts, /etc/fstab and other files

229. Native config overrides legacy config

231. Fully compatible with System V init scripts, /etc/fstab and other files

232. Native config overrides legacy config

233. Templating / instance mechanism

235. Fully compatible with System V init scripts, /etc/fstab and other files

236. Native config overrides legacy config

239. Fully compatible with System V init scripts, /etc/fstab and other files

240. Native config overrides legacy config

242. Ethernet control units

244. Fully compatible with System V init scripts, /etc/fstab and other files

245. Native config overrides legacy config

246. Templating / instance mechanism

247. Arbitrary number of sockets on launch

249. Fully compatible with System V init scripts, /etc/fstab and other files

250. Native config overrides legacy config

251. Templating / instance mechanism

252. Arbitrary number of sockets on launch

253. Supplies /dev/initctl and wtmp/utmp

256. Start/exit time of each daemon

258. Start/exit time of each daemon

259. Full restart of init at any time

261. Start/exit time of each daemon

262. Full restart of init at any time

263. Basic daemon startup coded in C

265. Start/exit time of each daemon

266. Full restart of init at any time

267. Basic daemon startup coded in C

268. Full Dbus introspection

273. OpenSuSE

275. OpenSuSE

276. Debian

278. OpenSuSE

279. Debian

280. Gentoo

281. ArchLinux

283. OpenSuSE

284. Debian

285. Gentoo

287. OpenSuSE

288. Debian

294. Don't drop user privileges

296. Don't drop user privileges

297. Don't write PID files

299. Don't drop user privileges

302. Don't drop user privileges

305. Don't drop user privileges

307. Sockets and stuff in unit file

308. systemd

309. systemd Don't be afraid ☺