The /etc/inittab file is a script that controls most of the boot sequence. It dictates what programs and scripts to launch and at what runlevels.
Ubuntu uses Upstart, as does Fedora 9 and later. There is no direct equivalent to /etc/inittab, as startup scripts run asynchronously. Each script in /etc/event.d serves a similar purpose to a line on a traditional inittab.
man 5 inittab
using i cloud
The inittab file contains descriptions of the run states that your system is allowed to assume. Configure it to contain the default runlevels your system will assume when it boots.
/etc/inittab Type [id:5:initdefault:]
The init program is the first program run after your kernel begins running. It is configured with the /etc/inittab file. By modifying your /etc/inittab file, you change your system configuration in the following areas:Start up system run level.Specify processes to be executed during system boot.Specify processes to be run when the specified runlevel is entered.Specify processes to be run on certain runlevels with actions like respawn so the process is restarted any time it terminates.Specify certain actions or processes to be run if certain signals or user actions are indicated.
Run level 1 is considered an adminstrative mode, usually for installing packages and so forth. In this situation, you want a minimal set of processes running, no other users logged in, and local filesystems mounted. It usually requires the /etc/inittab file for the definitions of what processes to start at different run levels. Run level s is for single user mode, usually considered an administrative mode as well, but for more of a basic environment; local file systems are not mounted and the /etc/inittab file does not have to exist. Usually, single user level is for repairing systems or troubleshooting the system.
/etc/hosts
A system determines its default runlevel through the configuration files typically located in /etc/inittab or, in newer systems using systemd, through the default target specified in the /etc/systemd/system/default.target file. The default runlevel or target indicates the state in which the system will start, such as multi-user mode or graphical mode. During the boot process, the init system reads this configuration to establish the appropriate environment and services to launch. If not explicitly set, the system may fall back to a predefined runlevel or target.
Boot Sequence: 1] Poweron. 2] PDC Activates and checks for CPU and memory and other peripheral connected to it. 3] Checks if AUTOBOOT Flag is on. If yes , its try to locate the Primary boot path. 4] And loads Initial system loader , from Primary boot path. 5] ISL Loads the secondery loader called hp-ux. 6] hpux loads the kernel /stand/vmunix 7] kernel starts first process swapper , and then init 8] Shell /sbin/pre_init_rc executes . 9] init locates /etc/inittab 10] /etc/inittab starts the system the default run level , mentioned with "initdefault" parameter. 11] Then executes /sbin/bcheckrc and activates LVM , it does following : 1) activates LVM (if appplicable). # 2) runs eisa_config in automatic mode # (if applicable). # 3) checks the file systems before mounting. # (the scripts required for file system specific # checking reside in /sbin/fs//bcheckrc) # 4) and anything else that should be done before # mounting any file systems. ------------------ It checks for the file /sbin/lvmrc and , /etc/lvmrc activates the LVM , if AUTO_VG_ACTIVATE=1 mentioned. 12 ]Then it spawns getty process , cons:123456:respawn:/usr/sbin/getty console console And it gives login : prompt. Raj
Boot Sequence: 1] Poweron. 2] PDC Activates and checks for CPU and memory and other peripheral connected to it. 3] Checks if AUTOBOOT Flag is on. If yes , its try to locate the Primary boot path. 4] And loads Initial system loader , from Primary boot path. 5] ISL Loads the secondery loader called hp-ux. 6] hpux loads the kernel /stand/vmunix 7] kernel starts first process swapper , and then init 8] Shell /sbin/pre_init_rc executes . 9] init locates /etc/inittab 10] /etc/inittab starts the system the default run level , mentioned with "initdefault" parameter. 11] Then executes /sbin/bcheckrc and activates LVM , it does following : 1) activates LVM (if appplicable). # 2) runs eisa_config in automatic mode # (if applicable). # 3) checks the file systems before mounting. # (the scripts required for file system specific # checking reside in /sbin/fs//bcheckrc) # 4) and anything else that should be done before # mounting any file systems. ------------------ It checks for the file /sbin/lvmrc and , /etc/lvmrc activates the LVM , if AUTO_VG_ACTIVATE=1 mentioned. 12 ]Then it spawns getty process , cons:123456:respawn:/usr/sbin/getty console console And it gives login : prompt. Raj
/etc/syslog.conf