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Questions tagged [init]

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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183
votes
6answers
89k views

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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2answers
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How does systemd use /etc/init.d scripts?

I just switched to debian jessie, and most things run okay, including my graphical display manager wdm. The thing is, I just don't understand how this works. Obviously my /etc/init.d/wdm script is ...
101
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4answers
291k views

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?
92
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5answers
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How to find out if a system uses SysV, Upstart or Systemd initsystem [duplicate]

Is there a simple way to find out which initsystem is being used e.g by a recent Debian wheezy or Fedora system? I'm aware that Fedora 21 uses systemd initsystem but that is because I read that and ...
92
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18answers
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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 and Ubuntu now use systemd, Ubuntu used to use Upstart (...
43
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5answers
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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 ...
41
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4answers
12k views

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) ...
39
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5answers
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How to disable X server autostart in Debian Jessie?

I have a remote machine running Debian 8 (Jessie) with lightdm installed. I want it to start in no-GUI mode, but I don't want to remove all X-related stuff to still be able to run it though SSH with ...
38
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7answers
52k views

Can root kill init process?

Can root kill init process (the process with pid 1)? What would be its consequences?
28
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1answer
7k 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 ...
27
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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 ...
27
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3answers
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If computers start counting at 0, why does the init process have a pid of 1?

Not much to put here in the body.
27
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2answers
1k views

Can a zombie have orphans? Will the orphan children be disturbed by reaping the zombie?

As I understand it, a zombie process has died but still exists as a placeholder in the process table until its parent (or init if the zombie is itself an orphan) checks its exit status. And my ...
26
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1answer
20k 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 ...
25
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3answers
224k views

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 linux-...
23
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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
22
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4answers
14k 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?
19
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1answer
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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, ...
18
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9answers
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How to read the shut down messages afterwards?

I'm using Lubuntu 11.10. Every time I shut down I can read FAIL in red letters, but I can not read more. So, how to read the log messages and try to solve the problem?
17
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2answers
53k views

Running a systemd service as a user other than root!

I created the following service, amos.service, and it needs to run as amos (member of the amos group) [Unit] Description=AMOS Service After=network.target [Service] User=amos Group=amos Type=simple ...
14
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3answers
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Why can't the kernel run init?

I've downloaded the Raspbian image on this page. I'm trying to compile a kernel that can be used to boot the image within qemu. I downloaded the Linux kernel source from kernel.org and ran: make ...
13
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2answers
11k 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 is ...
13
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2answers
6k views

Can the init process be a shell script in Linux?

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 ...
13
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4answers
8k views

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 I'...
13
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2answers
53k views

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. ...
12
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4answers
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Is systemd “malicious”? [closed]

Visiting some forum online that discuss about Debian and Xubuntu, I saw some users that add this line in the signature field: ...With no systemd... This line is showed with pride (it seems to me). ...
12
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1answer
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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 ...
12
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1answer
11k views

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, ...
11
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1answer
2k 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?
11
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3answers
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File in Ubuntu equivalent to /etc/inittab file in RedHat

What file in Ubuntu is equivalent to the /etc/inittab file in RedHat? In RedHat the /etc/inittab file contains the settings related to the runlevel in which you want to boot Linux.
11
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1answer
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what is the canonical way to start a daemon in rhel/centos-6 init script?

I found lots of good documentation for ubuntu's start-stop-daemon and there is a man page for a binary daemon. But from what I can tell the canonical way to start a daemon in a rhel/centos script is ...
10
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2answers
26k views

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?
7
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1answer
4k views

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?
7
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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
votes
5answers
18k views

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 instaed ...
7
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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 ...
7
votes
1answer
3k 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 ...
7
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2answers
11k views

How to delete (not disable/mask) a unit in Systemd?

Sometimes I make a new unit in mistake, and then I have to go to /etc/systemd to look for the unit and delete all of its associated files/scripts/links/etc. Is there a better way? Like a single ...
6
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2answers
3k 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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2answers
7k views

How can I make an executable run as a service?

On Ubuntu 18.04, I can start or stop some service by sudo service cron start/stop I can list some services by service --status-all The output matches the files under /etc/init.d/. I heard there ...
6
votes
2answers
462 views

Where is fsck run?

I was reading through all the things that are run during bootup and have seen that after mounting the rootfs, /sbin/fsck.ext4 is run and after that systemd is run. I was wondering where or how fsck is ...
6
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1answer
1k views

If systemd has replaced SystemV, why is it still there and who is running the show?

I'm running Debian 8 x64 and still learning it. One of the confusing things I've come across repeatedly on Debian and Ubuntu systems is there appear to be two ways of running and managing services: ...
6
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1answer
1k 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 for ...
6
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2answers
1k 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 ...
5
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3answers
2k views

What is the difference between “init” and “service manager”?

From When the operating system shuts down, how does a service manager know that it should sends SIGTERM and SIGKILL to its services? systemd IS BOTH the init and service manager What is the ...
5
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1answer
21k views

sudo reboot -> Failed to talk to init daemon

On my Raspberry Pi runs jessie. After installing mosquitto I can not run sudo reboot anymore. This error appears: "Failed to talk to init daemon.". What could be the problem? I have already ...
5
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1answer
2k 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
6k 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 ...
5
votes
1answer
1k 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 ...
5
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1answer
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What are the variables $remote_fs and $syslog on SysVinit LSB header?

From: https://wiki.debian.org/LSBInitScripts Add a block like this in the init.d script: ### BEGIN INIT INFO # Provides: scriptname # Required-Start: $remote_fs $syslog ...