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Full Discussion: Linux Changing Run Levels
Operating Systems Linux Debian Linux Changing Run Levels Post 302985771 by hicksd8 on Tuesday 15th of November 2016 04:41:17 AM
Old 11-15-2016
The bug in your system is that you don't have a /etc/inittab file. As far as I'm aware this file is always created at installation and the most you might do is edit it. Creating one from scratch is laborious and needs in-depth knowledge of exactly how you want the system to behave.

A typical Debian (Squeeze) inittab file looks like this:

Code:
 
 # /etc/inittab: init(8) configuration.
# $Id: inittab,v 1.91 2002/01/25 13:35:21 miquels Exp $

# The default runlevel.
id:2:initdefault:

# Boot-time system configuration/initialization script.
# This is run first except when booting in emergency (-b) mode.
si::sysinit:/etc/init.d/rcS

# What to do in single-user mode.
~~:S:wait:/sbin/sulogin

# /etc/init.d executes the S and K scripts upon change
# of runlevel.
#
# Runlevel 0 is halt.
# Runlevel 1 is single-user.
# Runlevels 2-5 are multi-user.
# Runlevel 6 is reboot.

l0:0:wait:/etc/init.d/rc 0
l1:1:wait:/etc/init.d/rc 1
l2:2:wait:/etc/init.d/rc 2
l3:3:wait:/etc/init.d/rc 3
l4:4:wait:/etc/init.d/rc 4
l5:5:wait:/etc/init.d/rc 5
l6:6:wait:/etc/init.d/rc 6
# Normally not reached, but fallthrough in case of emergency.
z6:6:respawn:/sbin/sulogin

# What to do when CTRL-ALT-DEL is pressed.
ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now

# Action on special keypress (ALT-UpArrow).
#kb::kbrequest:/bin/echo "Keyboard Request--edit /etc/inittab to let this work."

# What to do when the power fails/returns.
pf:powerwait:/etc/init.d/powerfail start
pn:powerfailnow:/etc/init.d/powerfail now
po:powerokwait:/etc/init.d/powerfail stop

# /sbin/getty invocations for the runlevels.
#
# The "id" field MUST be the same as the last
# characters of the device (after "tty").
#
# Format:
# <id>:<runlevels>:<action>:<process>
#
# Note that on most Debian systems tty7 is used by the X Window System,
# so if you want to add more getty's go ahead but skip tty7 if you run X.
#
1:2345:respawn:/sbin/getty 38400 tty1
2:23:respawn:/sbin/getty 38400 tty2
3:23:respawn:/sbin/getty 38400 tty3
4:23:respawn:/sbin/getty 38400 tty4
5:23:respawn:/sbin/getty 38400 tty5
6:23:respawn:/sbin/getty 38400 tty6

# Example how to put a getty on a serial line (for a terminal)
#
#T0:23:respawn:/sbin/getty -L ttyS0 9600 vt100
#T1:23:respawn:/sbin/getty -L ttyS1 9600 vt100

# Example how to put a getty on a modem line.
#
#T3:23:respawn:/sbin/mgetty -x0 -s 57600 ttyS3

I suggest you try injecting the above into your inittab at least down to the comment line "# Normally not reached" even if you don't copy the rest. That might restore some resemblance of normality.

Obviously, this whole mechanism is surrounded by security. You couldn't allow an ordinary user to use 'init' to change run levels; only root can do that. Also, why would an ordinary user want to know the runlevel of the system? If they are allowed to read inittab they certainly wouldn't be allowed to write to it. So there may be a simple explanation why 'who -r' doesn't work properly for a non-root user.
 

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inittab(4)						     Kernel Interfaces Manual							inittab(4)

NAME
inittab - Controls the initialization process SYNOPSIS
/etc/inittab DESCRIPTION
The inittab file provides the init program with instructions for creating and running initialization processes. The init program reads the inittab file each time init is invoked. The file typically contains instructions for the default initialization, the creation and control of processes at each run level, and the getty command, which controls the activation of terminal lines. Each line in the inittab file contains an entry that has four fields; each field is separated by a colon. There is no limit to the number of entries in the inittab file. The entry syntax is as follows: Identifier:Runlevel:Action:Command Specifies a fourteen character field used to uniquely identify an object. Specifies a twenty character field that defines the run levels in which the object is to be processed. Runlevel corresponds to a configuration of processes in a system. Each process spawned by the init command is assigned one or more run levels in which it is allowed to exist. The run levels are as follows: Specifies the halt state. Specifies multiuser state without network services. Specifies multiuser state with network services. Specifies single-user state. You can define multiple run levels for a process by specifying more than one run level character in any combination. Specifies a twenty char- acter field that tells init how to treat the specified process. init recognizes the following Action values: Specifies that if the process does not exist or if it dies, init starts it. If the process exists, init continues to process the inittab file. Specifies that if init enters a run level that matches the run level specified in the inittab file entry, it starts the process and waits for its termination. As long as init continues in this run level, it does not act on subsequent reads of the entry in the inittab file. Specifies that if init enters a run level that matches the run level specified in the inittab file, it starts the process and does not wait for its termination. When the process stops, init does not restart it. If init enters a new run level where the process is still running from a previous run- level change, init does not restart the process. Specifies that when init first executes and reads the inittab file, it processes this entry. The init program starts the process and does not wait for its termination. When the process stops, init does not restart it. The run level specified in this inittab file entry should be the default run level, or it must match the run level in which init operates at boot time. Specifies that when init first executes and reads the inittab file, it processes this inittab file entry. The init program starts the process, waits for its termination and, when it dies, does not restart the process. (This value exists only for SVID3/SVR4 com- patibility.) Specifies that if init receives the SIGPWR power fail signal, it executes the process associated with this line. (This value exists only for SVID3/SVR4 compatibility.) Specifies that if init receives the SIGPWR power fail signal, it executes the process associ- ated with this line and waits until the process terminates before continuing processing the inittab file. Specifies that if the process associated with this line is currently running, init sends the warning signal SIGTERM and waits 20 seconds before sending the kill signal SIGKILL. If the process does not existent, init ignores the inittab entry. Specifies that a line with this action is processed when init is originally invoked. The init program uses this line to determine the run level to enter originally. It determines this by taking the highest run level specified in the run level field and using that as its initial state. If the run level field is empty, this is inter- preted as 0s23, causing init to enter run level 3. If init does not find an initdefault entry in the inittab file, it requests an initial run level from the operator. Specifies that entries of this type are executed before init tries to access the console. This inittab file entry should be used only to initialize devices on which init could attempt to request a run level. Specifies a 1024 character field that contains the sh command to be executed. The command is prefixed with exec. Any legitimate sh syntax can appear in the command field. Com- ments can be inserted be specifying a number sign (#). The line continuation character can be placed at the end of a line. EXAMPLES
The following is an example of an inittab file entry for a terminal line: tty01:23:respawn:/usr/sbin/getty /dev/tty08 9600 vt100 FILES
Specifies the command that initializes and controls terminal lines. RELATED INFORMATION
Commands: init(8), getty(8) Functions: kill(2) delim off inittab(4)
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