systemd

Question 1

which dictates how a systemd-based Linux computer will boot up. An innovation of systemd is that it removed the need to have shell scripts The problem with Bash scripts is that they have to be ran
through the Bash interpreter, and these end up spawning new processes for each command within the shell script. Each one of these processes then have to open up a library file for the functions that a command will need. All in all, this is an inefficient use of time to get services started, which in turn slows down the speed with which the system could boot or a service to start.

Answer 1

systemd unit files

Question 2

To get around this problem the developers of systemd replaced many of the shell scripts
with equivalent functionality written in C code, which is then compiled to run much faster.
Not all shell scripts could be replaced, but each one that is replaced by C code is a win for speed and efficiency. This does not mean that you cannot use the older System V init scripts anymore.
Systemd still has a compatibility mechanism to read these older script files and still use them.
The caveat is that the older System V init scripts will not enjoy the same robustness that they would get from a patch daemon that works directly with systemd, such as socket activation, parallel startup,
and other features. Nonetheless, the point remains that even though systemd is different, it is still backwards compatible.

Answer 2

bash script problem

Question 3

what are known as unit files default location where unit files are installed by packages.

Answer 3

instead of bash files systemd utilizes

Question 4

location of first unit file and it should never be edited

Answer 4

/usr/lib/systemd/system

Question 5

this unit file is safe to edit any unit files in this location will take precedence
over any other unit files on the system.

Answer 5

/etc/systemd/system

Question 6

The other location of systemd unit files is the runtime location

Answer 6

/run/systemd/system

Question 7

can view all of the unit files on your computer by running systemctl and the output of this command is divided up into different sections,each one pertaining to a particular type of unit

Answer 7

list-unit-files

Question 8

unit that syncs up other units when the computer boots or changes state

Answer 8

target

Question 9

multi-user system, similar to what runlevel 3 provided

Answer 9

multi-user.target

Question 10

multi-user system with a desktop environment, similar to what runlevel 5 provided

Answer 10

graphical.target

Question 11

pulls in a basic system and file system mounts and provides a rescue shell

Answer 11

rescue.target

Question 12

basic system, used during the boot process before another target takes over

Answer 12

basic.target

Question 13

system initialization

Answer 13

sysint.target

Question 14

defines the target unit configuration

Answer 14

man 5 systemd.target

Question 15

listing of all target units and definitions

Answer 15

man 7 systemd.special

Question 16

Show all unit files for available targets

Answer 16

Target Unit: systemctl list-unit-files -t target

Question 17

Show all loaded and active unit files

Answer 17

Target Unit:systemctl list-units -t target

Question 18

Target Unit: systemctl get-default

Answer 18

List out the default target

Question 19

Change the default target to a different target

Answer 19

Target Unit:systemctl set-default

Question 20

Will change the running state of the system from the current target to a different target

Answer 20

Changing Target:systemctl isolate <target></target>

Question 21

Almost identical to the System V

Answer 21

Changing Target:systemctlrescue

Question 22

allows the root user to repair a system

Answer 22

Changing Target: Init single-user mode

Question 23

Will run the reboot.target. Same thing as just typing ‘reboot’ at the prompt

Answer 23

Changing Target:systemctlreboot

Question 24

Will perform a complete shutdown of the system by isolating the system to the poweroff.target. Same thing as just typing ‘poweroff’ at the prompt

Answer 24

Changing Target:systemctl poweroff