init is the first actual process (PID 1) spawned during the boot sequence of a UNIX system. Some systems may rely on alternative solutions such as systemd or Upstart (Ubuntu).

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What are the pros/cons of Upstart and systemd?

It appears systemd is the hot new init system on the block, same as Upstart was a few years ago. What are the pros/cons for each? Also, how does each compare to other init systems?
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What is the difference between reboot , init 6 and shutdown -r now?

I just want to know difference between in reboot init 6 shutdown -r now and which is the safest and the best?
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Is there any UNIX variant on which a child process dies with its parent?

I have been studying the Linux kernel behaviour for quite some time now, and it's always been clear to me that: When a process dies, all its children are given back to the init process (PID 1) ...
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4answers
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What exactly does init do?

I am creating a linux distro and now I need an init program. I can code in c really well and I know quite a bit about linux (not much but I've been using arch linux for development for 4 years), so I ...
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10answers
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Detect init system using the shell

This may have more to do with detecting operating systems, but I specifically need the init system currently in use on the system. Fedora 15 now uses systemd, Ubuntu uses Upstart, while others use ...
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3answers
1k views

If computers start counting at 0, why does the init process have a pid of 1?

Not much to put here in the body, the question is self explanatory.
23
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1answer
2k views

How does systemd survive a kill -9?

Between the recent "Why does 'kill -9 0' end my console session" and "How to get a kernel panic" questions, I got a bur under my saddle and tried kill -9 1 on a mostly up-to-date Arch linux laptop. I ...
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7answers
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Start tomcat at startup with administrative privileges

I need one process run before log in to system. How to run it like services? how do I make services in Linux? In Ubuntu and Fedora? The service is customized tomcat
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Can root kill init process?

Can root kill init process (the process with pid 1)? What would be its consequences?
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2answers
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How can I kill a <defunct> process whose parent is init?

Transmission is intermittently hanging on my NAS. If I send SIGTERM, it doesn't disappear from the process list and a <defunct> label appears next to it. If I send a SIGKILL, it still doesn't ...
16
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1answer
6k views

init process: ancestor of all processes?

I have always learned that the init process is the ancestor of all processes. Why does process 2 have a PPID of 0? $ ps -ef | head -n 3 UID PID PPID C STIME TTY TIME CMD root ...
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1answer
766 views

Why does running `killall init` as user log me out?

On multiple computers running Ubuntu 14.XX, I ran the command "killall init" as user, and was immediately logged out. I could log back in again without a problem. Why is this? What's going on behind ...
8
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1answer
822 views

Why does “kill -9 0” end my console session?

I just wonder why kill -9 0 ends my tty console session? What exactly is PID 0, it is not listed on a ps aux?
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Launch process as another user/group (in init.d script)

I am editing a init.d script. The init.d script runs a utility script which then runs an process. From either bash scripts how would I make it launch the main process as a specific user and group?
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1answer
624 views

Restarting init without restarting the system

In this question on security SE, the accepted answers states that For example, /sbin/init uses glibc [the vulnerable lib], and restarting that without a reboot is non-trivial. Now, non-trivial ...
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4answers
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Add item to inittab on OpenSuse 12.1

I am currently working on a project which needs to be added to inittab so that the program loads during startup. The program that I am trying to start is a c# mono application. I have created a ...
7
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1answer
358 views

Init as a shell script

I was going through a tutorial on setting up a custom initramfs where it states: The only thing that is missing is /init, the executable in the root of the initramfs that is executed by the ...
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How to fix boot into initramfs prompt and “mount: can't read '/etc/fstab': No such file or directory” and “No init found”?

Installing a new system using a GPT partitioned disk dedicated to a single partition, ext4 formatted, extlinux (version 4.05) as bootloader, Ubuntu Core version 13.10 amd64 as rootfs, and Ubuntu ...
7
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1answer
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How to find out in which order /etc/init.d scripts are load on Debian?

I want to run one sysvinit script before another and figured out how to do that. To make sure, this actually happens in the the order I like, I would like to see a list, in which order that happens. ...
6
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4answers
1k views

New parent process when the parent process dies

In UNIX, when a parent process disappears, I thought that all child processes reset init as their parent. Is this not correct all the time? Are there any exceptions?
6
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2answers
734 views

What happens if I set default system runlevel to 0 or 6?

What I understand from runlevels is that in each level some programs have permission to be executed and some don't. runlevel 3 boots system into CLI and runlevel 5 starts the default GUI. But I don't ...
6
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3answers
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File in Ubuntu equivalent to /etc/inittab file in RedHat

I searched a lot but can't get any solution. My question is what file in Ubuntu is equivalent to /etc/inittab file in RedHat. In RedHat /etc/inittab file contains the setting related to runlevel in ...
6
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1answer
617 views

inittab '-' character in process field

I have a an inittab file with the following entry: console::askfirst:-/bin/ash According to this Man page a '+' character in the process field means init will not do utmp and wtmp accounting ...
6
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1answer
2k views

How Do I Add My Own Daemons in Arch Linux? (BSD-style init)

I have created a symlink to a start/stop/etc. wrapper bash script in /etc/rc.d, added it to DAEMONS=() in rc.conf, but the process it points to isn’t starting on boot, and isn’t showing up in the ...
6
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2answers
800 views

How do I start my service at boot-time?

I'm trying to run a CherryPy app on my NetBSD 5.1 box. To have it start automatically, I've added this line to my /etc/rc.local: /bin/httpd & When I boot the machine, some of the output of the ...
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2answers
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What can make passing init=/path/to/program to the kernel not start program as init?

I'm trying to debug an init script on a Linux system; I'm trying to pass init=/bin/sh to the kernel to make it start sh without starting init so I can run through the init sequence manually. What ...
6
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1answer
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How can you get console backgrounds for Arch Linux?

I have tested out openSUSE and found that the tty1 is a bit different from other systems as the tty has got a background. I know that Knoppix has a tux penguin for each core the computer has, but I'm ...
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1answer
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What will happen if I run the command init in my Ubuntu Gnome terminal?

command init seems to be the first process running after each booting. If I init in my Ubuntu Gnome terminal, will that restart my OS?
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2answers
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Why does debian and ubuntu default to runlevel 2?

I never thought about this before, but I was wondering why they chose runlevel 2. Every other distro and OS I've used default to runlevel 3 (with the exception of AIX which also defaults to runlevel ...
5
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1answer
385 views

init: is it a user thread or a kernel thread?

init is the first task executed after kernel is loaded, right? Then who is its owner. also I can see [swapper/0] [swapper/1] ..... [swapper/7] having pid 0 PID PPID CPU TASK ST %MEM ...
5
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1answer
323 views

What does `init [2]` mean in the COMMAND column of ps?

Reading What do the brackets around processes mean? I understand that the executable name is printed. Linux ps man page: Sometimes the process args will be unavailable; when this happens, ps will ...
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2answers
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Why is a service being started if it isn't mentioned in /etc/init.d?

After a clean install of Fedora 17 and distcc-server, I did a service distccd start, which completed successfully. man service indicates that it would merely be running the distccd script at ...
5
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1answer
55 views

What is a sync during kernel boot?

If something prevents a Linux system from booting, it is common to see this message: kernel panic - not syncing: [Error Message] But what does "not syncing" mean? What exactly isn't syncing? The ...
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637 views

When running to a run level does it execute previous run levels?

If I tell my system to go to run level 3 does that mean that it first runs through run level 0, 1, 2, and then finally runs through run level 3? I thought the answer to this question was yes. But ...
4
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1answer
1k views

How to trick an init script into returning 0

I have a init script which is poorly designed because it does not conform to the Linux Standard Base Specifications The following should have an exit code of 0 if running, and 3 if not running ...
4
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1answer
2k views

How does init determine which devices to modprobe?

I'm building a totally custom initramfs for a netbooting project and in the process learning a lot about it, but I'm a little puzzled by the loading of modules. I know modprobe can be used to load ...
4
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1answer
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Minimal Linux with kernel and BusyBox: /etc/inittab is ignored, only /init is executed

I managed to create a small and fully functional live Linux CD which contains only kernel (compiled with default options) and BusyBox (compiled with default options + static, all applets present, ...
4
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1answer
2k views

When would you use pivot_root over switch_root?

I'm wanting to understand the Linux init process better in order to netboot a system over ceph rather than nfs. In the process I've come across two forms of switching root. One called switch_root, ...
4
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1answer
86 views

/sbin/init is shared object?

I know 'init' is first process that is started after the kernel is loaded, but there is an ambiguity for me. If it is a process it must have a binary executable file. However, the following shared ...
4
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1answer
228 views

SIGKILLing after a grace period

I've seen a lot of process managers that try to do this. It was my understanding that you should only use SIGTERM to kill a process. The process could take an unknown amount of time to clean up after ...
4
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1answer
57 views

how to completely blank video output on boot (no kernel logging, grub output, etc.)

So, this is an inversion of the classic question: "Why is my terminal blank on boot?" -- How do I make my terminal blank on boot? I'm creating a Debian Wheezy system with GRUB as the boot loader that ...
3
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How can I run a daemon with custom parameters

I am wondering how I can run a daemon, in this case NTP, with custom parameters. For example in my Ubuntu PC I observe that I've got ntpd running this way: $ ps aux | grep ntpd ntp 5936 ... 0:00 ...
3
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2answers
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autossh in /etc/inittab

I have setup ssh tunnel to be able to connect a target computer behind NAT. I have put the following into /etc/inittab on the computer: tu:2345:respawn:/usr/bin/autossh -M 20000 -f -n -N -T -R ...
3
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1answer
345 views

Rolling your own init: How to shutdown/restart?

After reading this answer, I thought it would be funny to roll my own init on Python, so I wrote this in /init-python. #!/usr/bin/python3 import os import subprocess # Make / writable! ...
3
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1answer
878 views

How do systemd and chkconfig interact with respect to services and runlevels?

I recently updated some of our machines to Fedora 17. I have noticed that there are some services that I can configure their runlevels using chkconfig, while others don't appear there at all, and can ...
3
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1answer
386 views

Init script leaves thousands of defunct processes

My problem is that I have an init script that is generating thousands of defunct bash processes. My goal is to have a program called "fr24feed" in its own screen session on boot. After looking at ...
3
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1answer
488 views

Relationship among runlevels and virtual terminals (TTY)

When I switch from rulevel 5 to 3 (with init command) and I press CtrlAltF1 up to F7, I realize that now I’m on TTY1 instead of TTY7 and when I switch back to runlevel 5 I return back to TTY7. Why? ...
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1answer
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“INIT: version 2.86 reloading” - cause and fix?

INIT: version 2.86 reloading appears on screen. Encountered this error and it seems there is no other way to fix this other than rebooting the system. unable to ssh in, unable to login via ...
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3answers
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Why is my Debian jessie always in runlevel 5?

I have configured the lines in /etc/inittab as follows: # The default runlevel. id:2:initdefault: But after logging in the output of runlevel is as follows: N 5 So why am I in runlevel 5 ...
2
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1answer
485 views

Ubuntu 11.04 Startup Applicatation vs /etc/init.d

Is there any difference between these two methods for application to start on boot? I need an application to start before a logon occurs and am questioning whether or not Ubuntu's Startup Application ...