Системно и Мрежово Администриране на Linux 1

• System V Init
• Upstart
• Systemd

System V sequential

  Kernel -> init -> app1 -> app1 -> app3 ... -> login 

System V parallel

  Kernel -> init -> app1 -> app2 ----> app3 -> app6 ----> app7  -> login
                                   |-> app4           |-> app8
                                   \-> app5           |-> app9
                                                           \-> app10

Upstart

  Kernel -> init -> app1 -> app2 ----> app3
                                   |-> app4
                                   |-> app5
                                   |-> app6 -> login
                                   |-> app7
                                   |-> app8
                                   \-> app9

Systemd

  Kernel -> init --> app1
                 |-> app2
                 |-> app4
                 |-> app5
                 |-> app6
                 |-> app7 -> login
                 |-> app8
                 \-> app9

System V init
Defines the notion of runlevels
/etc/inittab
/etc/rc.d or /etc/init.d
/etc/rcX.d or /etc/rc.d/rcX.d
Comands used for management: cp, mv, ln, rm


Upstart - http://upstart.ubuntu.com/
Also uses the notion of runlevels
/etc/init/
/etc/inittab
Commands used for management: start, stop, status, initctl


Systemd - http://www.freedesktop.org/wiki/Software/systemd/
/etc/systemd/
/lib/systemd/
Change the default target:
ln -s /usr/lib/systemd/system/multi-user.target /etc/systemd/system/default.target Commands used for management: systemctl, systemd-sysv-convert