Linux: Init Process and PC Boot Procedure PC Boot and Linux Init Process: BIOS: The Basic Input/Output System is the lowest level interface between the computer and peripherals. The BIOS performs integrity checks on memory and seeks instructions on the Master Boor Record (MBR) on the floppy drive or hard drive. The MBR points to the boot loader (GRUB or LILO: Linux boot loader). The Linux Init Processes: SysV init or systemd: The Linux and Unix SysV heritage began with the "sysvinit" process which used the /etc/inittab configuration file to drive the execution of init scripts and configuration of terminal and GUI interfaces. Systemd is used in later versions of Linux (Fedora 15+, RHEL 7, OpenSUSE 12.1+, ...) which is compatible with Unix SysV and Linux Standard Base (LSB) init scripts. Ubuntu 12.04+, 14.04 uses a hybrid system called upstart which includes SysV runlevel specific start scripts in /etc/rc.#/ but also systemd scripts for those services which have been ported in /lib/systemd/system/. Launching processes: SysV init:
Linux Directory Structure (File System Structure) Explained with Examples by Ramesh Natarajan on September 8, 2010 Have you wondered why certain programs are located under /bin, or /sbin, or /usr/bin, or /usr/sbin? For example, less command is located under /usr/bin directory. Why not /bin, or /sbin, or /usr/sbin? In this article, let us review the Linux filesystem structures and understand the meaning of individual high-level directories. 1. / – Root Every single file and directory starts from the root directory.Only root user has write privilege under this directory.Please note that /root is root user’s home directory, which is not same as /. 2. Contains binary executables.Common linux commands you need to use in single-user modes are located under this directory.Commands used by all the users of the system are located here.For example: ps, ls, ping, grep, cp. 3. 4. Contains configuration files required by all programs.This also contains startup and shutdown shell scripts used to start/stop individual programs.For example: /etc/resolv.conf, /etc/logrotate.conf
insserv - Enable an installed system init script maverick (8) insserv.8.gz Provided by: insserv_1.14.0-2_i386 insserv - Enable an installed system init script insserv [-v] [-c <config>] [-p <path>] [-d] [-f] [[/]path/to/init.d/]script ... insserv [-v] [-c <config>] [-p <path>] [[/]path/to/init.d/]script[,start=<lvl1,lvl2,...>,stop=<lvl1,lvl2,...>] insserv [-v] [-c <config>] [-p <path>] -r [-d] [-f] [[/]path/to/init.d/]script ... insserv -h Currently there exists nine options for insserv. -v, --verbose Write out what is currently going on. [[/]path/to/init.d/] Relative or absolute path to the init scripts base directory. Beside using the extensions ,start=<lvl1,lvl2,...> and ,stop=<lvl1,lvl2,...> it is possible to use override files replace a LSB comment header or simple provide a missing LSB comment header. The exit codes have the following conditions: 0 Service was successfully installed or removed 1 Service was not installed or removed Boot scripts sometimes lack a LSB comment header. init(7), startpar(8). Werner Fink <feedback@suse.de>