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LPIC 101-500 > 101.3 Change runlevels / boot targets and shutdown or reboot system > Flashcards

101.3 Change runlevels / boot targets and shutdown or reboot system Flashcards

1
Q

Define run level.

A

A run level is a predefined configuration that the computer will operate within.

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2
Q

In how many run levels can a computer operate at a time?

A

One at a time only.

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3
Q

What is the purpose of Runlevel 1?

A

Single user mode. Used for maintenance tasks and repair functionality.

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4
Q

What is the purpose of runlevel 2?

A

Multiple users can log again, but without any networking interface nor are there any remote file systems mounted.

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5
Q

What is the purpose of runlevel 4?

A

Not used, but it is available should an administrator want to set up a custom run level environment

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6
Q

What is the purpose of runlevel 5?

A

Not used, but it is available should an administrator want to set up a custom run level environment

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7
Q

What is the purpose of runlevel 6?

A

Reboot runlevel (init stops services and restarts the system going back through the complete computer bootup sequence once again).

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8
Q

What is the purpose of runlevel 3?

A

Multiple users can log with networking capabilities.

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9
Q

How do you read the following in the /etc/inittab file?

id : 3 : initdefault _

A

: : :

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10
Q

Where are the scripts that init works with to get a system up and running?

A

In RHEL: /etc/rc.d

In Debian: /etc/init.d

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11
Q

Within /etc/rc.d/rc3.d directory (for runlevel 3), what do the numbers mean after the letters K and S?

A

The numbers after the letters indicate the numerical order in which the scripts are to be killed and started.

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12
Q

What is an advantage upstart has over init?

A

Upstart can start services in parallel to one another rather than waiting on one service to start before it could start up the next one.

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13
Q

What will happen if Upstart detects a service that has stopped working unexpectedly?

A

Upstart monitors the services that it works with. If a service stops working Upstart will attempt to get it running again.

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14
Q

Where will the Linux kernel look for an initialization daemon named init?

A

/sbin directory ( /sbin/init )

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15
Q

List the order of the init boot sequence.

A

/sbin/init > /etc/inittab > /etc/rc.d/rc.sysinit > /etc/rc.d/rcX.d > login

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16
Q

In the upstart boot sequence, as file systems come online, startup will run which script?

A

The /etc/init/rc-sysinit.conf script

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17
Q

What does the rc-sysinit.conf script do?

A

It tells init to switch into the default run level via the run level command.

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18
Q

What does Linux call a change in the system that would trigger an Upstart job?

A

An event

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19
Q

When will Upstart stop a service?

A

Upstart will only kill a service if an event calls for it or if an administrator manually stops it.

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20
Q

What is the initial state of an Upstart job?

A

Waiting. It isn’t doing anything yet, but is just waiting to do something.

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21
Q

What does the Starting state mean?

A

The starting state means that the job itself is about to start.

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22
Q

What does the Stopping state mean?

A

The stopping state is an interim state where the job has processed a section of its configuration known as pre-stop. The job is not actually stopping at this point.

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23
Q

What does the Running state of a job mean?

A

A job’s running state means that the job is running.

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24
Q

What does the killed state mean in Upstart?

A

The killed state is where the job is actually stopping.

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25
Q

What does the post-stop job state mean?

A

The post stop state is where the job has completely stopped.

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26
Q

What job state follows after post-stop?

A

It goes back into the waiting state.

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27
Q

What is the order of the Upstart jobs?

A

Waiting > Starting > Running > Stopping > Killed > Post-stop > (Waiting …)

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28
Q

What is an innovation of Systemd?

A

Systemd removed the need to have shell scripts.

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29
Q

What language is used to write Systemd functionalities?

A

Systemd functionalities are written in C code.

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30
Q

Is Systemd backwards compatible with System V bash init scripts?

A

Yes, they are, although systemd C code is faster, more robust and more efficient.

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31
Q

What does systemd use instead of bash init scripts?

A

Systemd utilizes what are known as unit files.

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32
Q

Where are the systemd unit files that take precedence on the system?

A

The systemd unit files that take precedence on the system are the ones located in /etc/systemd/system

33
Q

How can you view all of the unit files on your computer?

A

By running #systemctl list-unit-files

34
Q

How can you view a unit file on the system?

A 
Use the command:
#systemctl cat something.unit
35
Q

What do systemd unit files use to go to /sbin/init?

A

A symbolic link.

36
Q

What command can you use to verify what run level you are currently in?

A

runlevel

37
Q

What does the output of the runlevel command display?

A

$ runlevel
N 3
———–
N=previous run level - 3=current runlevel

38
Q

What are 2 ways you can change runlevels in an init system?

A

1) #telinit # (# = runlevel you wish)

2) #init # ( # = runlevel you wish)

39
Q 
What does this output mean?
# runlevel
5 3
A

We were previously in runlevel 5 and now are in in runlevel 3

40
Q

In system V init and upstart systems, where does the telinit # command pull the info from?

A

We pull this information out of the /etc/inittab file

41
Q

What is a target unit file in systemd systems?

A

It dictates the type of environment that you would work in.

42
Q

What is a target unit purpose?

A

A target unit’s purpose is to synchronize with the other units on a computer when it boots up or when it is instructed to change states.

43
Q

Run Level 5 provided on a classic init system is the same as the _____ in a systemd system.

A

Graphical.target

44
Q

What target gets started right after Systemd takes over for the kernel and gets the basic system started?

A

sysint.target

45
Q

What target would you use to get into a multi user command line environment?

A

Multi-user.target

46
Q

Run level 3 on a classic init system is analogous to what target in a systemd system?

A

Multi-user.target

47
Q

What target is the same as runlevel 1 in a systemd system?

A

rescue.target

48
Q

What do you call the target that provides an isolated environment for the root user to perform repairs on the system?

A

rescue.target

49
Q

What is the name of the target that provides a basic system that is utilized during the boot process before the system changes into its default target?

A

Basic.target

50
Q

What command would you use to shut off the system using the runlevels?

A

telinit 0

51
Q

What command would you use to look at all of the target unit files on our system?

A

systemctl list-unit-files -t

52
Q

You can change the default target to something else by using this command:

A 
#systemctl set-default +targetname:
#systemctl set-default multi-user.target
53
Q

What command do you use to power off a system using targets?

A

systemctl poweroff

54
Q

What command do you use to log into rescue mode in systemd systems?

A

systemctl rescue

55
Q

What system V init command will reboot a computer?

A

telinit 6

56
Q

What is a simple command to reboot a Linux system?

A

reboot

57
Q

What command do you use to reboot a system and specify a time when we want the system to reboot?

A

shutdown -r now

58
Q

What command can you use to send messages to other users and let them know a system will be rebooted?

A 
#wall
(type message on next line) and hit crtl+D
59
Q

What is the simplest way to power off a system?

A

poweroff

60
Q

On an older upstart or System V init system, what command can you use to power off a system?

A

telinit 0

61
Q

To power off a computer, what command do you use to specify a time to power it off?

A

shutdown -h 1 minute

62
Q

What does ACPID stand for?

A

Advanced Configuration and Power Interface.

63
Q

What does usually the ACPID daemon monitor?

A

Events that typically involve power management such as :
+powering off the computer
+putting the computer to sleep in a suspend mode +hibernating the computer

64
Q

What runs on top init?

A

Upstart

65
Q

What target invokes a graphical desktop?

A

graphical.target

66
Q

In the upstart boot sequence, what does the startup check in the /etc/init/rc-sysinit.conf script?

A

It checks to see if there is an /etc/inittab file to see if there are any configuration options set there.

67
Q

What does the Advanced Configuration and Power Interface daemon do?

A 
It registers system events such as
\+pressing the power button
\+ closing the laptop lid
\+the ctl+alt+del sequence
\+mouse movement or pressing a key if the computer is asleep to wake it up.
68
Q

How do you isolate a target to change to another target?

A

systemctl isolate nameoftarget

69
Q

What does it mean that a symbolic link has a letter S or a letter K within /etc/rc.d/rcX.d directory?

A

Beginning with a K = services to be killed.

Beginning with an S = scripts are to be started.

70
Q

What user do you have to be logged on as to change runlevels in an init system?

A

Root

71
Q

Within the contents of the /etc/rc.d/rc3.d directory (for runlevel 3), you will find:

A

Symbolic links back to the original script files under /etc/init.d.

72
Q

What user can login in run level 1?

A

Typically only the root user is allowed to log into the system.

73
Q

What is the purpose of Runlevel 0?

A

+Halts the computer (init runs scripts that stops services and power off the system).

74
Q

If you’re on a Linux distro using Systemd, what commands can you use to power off the computer?

A 
#systemctl isolate poweroff.target
#systemctl isolate shutdown.target
75
Q

In a systemd system, what command can you use to reboot the computer?

A

systemctl isolate reboot.target

76
Q

What command would you use to look at all of the target unit files currently active on your system?

A

systemctl list -units -t target

77
Q

How can you modify what runlevel to land on without changing the /etc/inittab file?

A
  1. Reboot the computer (#reboot)
  2. Interrupt the boot sequence
  3. Enter GRUB menu
  4. Press A to modify the kernel arguments
78
Q

What do you need to do to change the current running target to another one?

A

You need to isolate the target.

79
Q

Does Upstart start and stop services in an asynchronous manner?

A

Yes.

LPIC 101-500 (24 decks)

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