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

2. systemd A new init system for Linux

3. systemd A new init system for Linux Makes booting faster

4. systemd A new init system for Linux Makes booting faster

5. How?

6. systemd How does init work anyway?

7. System V init The init process is started by the kernel

8. System V init The init process is started by the kernel

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

10. System V init The init process is started by the kernel

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 ...

13. System V init The init process is started by the kernel

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.

17. systemd A new init system for Linux Makes booting faster

18. Do it in parallel?

19. systemd A new init system for Linux Makes booting faster

20. Do it in parallel? Dependencies!

21. upstart A new init system for Linux

22. upstart A new init system for Linux Makes booting faster by encoding dependencies between modules

23. upstart A new init system for Linux Makes booting faster by encoding dependencies between modules

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

25. upstart Then everyone gets kittens!

26. upstart A new init system for Linux Makes booting faster by encoding dependencies between modules

27. upstart then resolves these dependencies and starts up as many things as it can in parallel Only problem is...

28. upstart A new init system for Linux Makes booting faster by encoding dependencies between modules

29. upstart then resolves these dependencies and starts up as many things as it can in parallel Only problem is... Encoding the dependencies.

30. upstart A new init system for Linux Makes booting faster by encoding dependencies between modules

31. upstart then resolves these dependencies and starts up as many things as it can in parallel Only problem is... Domain-specific language required...

32. upstart A new init system for Linux Makes booting faster by encoding dependencies between modules

33. upstart then resolves these dependencies and starts up as many things as it can in parallel Only problem is... We're still starting too much...

34. Booting a system What actually needs to get started?

35. Booting a system What actually needs to get started? System V init: Try to think of everything and boot it in what we hope is the right order...

36. Booting a system What actually needs to get started? System V init: Try to think of everything and boot it in what we hope is the right order... upstart: Try to think of everything, resolve dependencies and hope that works...

37. Booting a system How do we know what needs to get started?

38. Booting a system How do we know what needs to get started? We wait for something to use it!

39. Booting a system How do we know what needs to get started? We wait for something to use it!

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

41. Booting a system How do we know what needs to get started? We wait for something to use it!

42. Then we catch the request and start the daemon. Is there something that already works like this?

43. Booting a system How do we know what needs to get started? We wait for something to use it!

44. Then we catch the request and start the daemon. Is there something that already works like this? Yes:

45. Booting a system How do we know what needs to get started? We wait for something to use it!

46. Then we catch the request and start the daemon. Is there something that already works like this? Yes: xinetd

47. xinetd List of sockets

48. xinetd List of sockets

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

50. xinetd List of sockets

51. When a connection is made, start the related daemon Per-socket startup – e.g. rsync, nrpe

52. xinetd List of sockets

53. When a connection is made, start the related daemon Per-socket startup – e.g. rsync, nrpe

54. Hand socket to daemon – 'wait' option

55. Sockets in startup Lots of services use sockets

56. Sockets in startup Lots of services use sockets /var/run/cups/cups.sock

57. Sockets in startup Lots of services use sockets /var/run/cups/cups.sock

58. /var/run/dbus/system_bus_socket

59. Sockets in startup Lots of services use sockets /var/run/cups/cups.sock

60. /var/run/dbus/system_bus_socket

61. /var/run/rpcbind.sock

62. Sockets in startup Lots of services use sockets /var/run/cups/cups.sock

63. /var/run/dbus/system_bus_socket

64. /var/run/rpcbind.sock

65. /dev/log

66. systemd - sockets Work out what sockets we need to set up

67. systemd - sockets Work out what sockets we need to set up

68. Set them all up in parallel

69. systemd - sockets Work out what sockets we need to set up

70. Set them all up in parallel

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

72. systemd - sockets Work out what sockets we need to set up

73. Set them all up in parallel

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

75. systemd - sockets Work out what sockets we need to set up

76. Set them all up in parallel

77. When the socket is opened, start up its related daemon and hand the socket to it Only that application gets paused

78. systemd - sockets Work out what sockets we need to set up

79. Set them all up in parallel

80. When the socket is opened, start up its related daemon and hand the socket to it Only that application gets paused

81. Only for that request

82. systemd - sockets Work out what sockets we need to set up

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

86. systemd - sockets Work out what sockets we need to set up

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

91. systemd - sockets Work out what sockets we need to set up

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

95. Same logic for filesystems autofs!

96. systemd – and others... This isn't actually new

97. systemd – and others... This isn't actually new Mac OS X - launchd

98. systemd – and others... This isn't actually new Mac OS X – launchd

99. xinetd!

100. systemd A new init system for Linux Makes booting faster

101. systemd A new init system for Linux Makes booting faster Start processes in parallel

102. systemd A new init system for Linux Makes booting faster Start processes in parallel

103. Start fewer processes

104. systemd – results so far System V init: [paulway@tachyon ~]$ echo $$ 2440

105. systemd – results so far System V init: [paulway@tachyon ~]$ echo $$ 2440 MacOS: 154

106. systemd – results so far System V init: [paulway@tachyon ~]$ echo $$ 2440

107. Lennart's system: grep: 77 times MacOS: 154

108. systemd – results so far System V init: [paulway@tachyon ~]$ echo $$ 2440

109. Lennart's system: grep: 77 times

110. awk: 92 times MacOS: 154

111. systemd – results so far System V init: [paulway@tachyon ~]$ echo $$ 2440

112. Lennart's system: grep: 77 times

113. awk: 92 times

114. sed: 74 times MacOS: 154

115. systemd – managing processes System V init also restarts things

116. systemd – managing processes System V init also restarts things

117. Then they go off and do what they like