Scheduling

Question 1

atd vs crond

Answer 1

atd: onet ime jobs
crond: recurring jobs

Question 2

Which commands to use to schedule jobs

Answer 2

one off: at
recurring: crontab

Question 3

Determine which jobs are schedule for one time execute

Answer 3

atq

Question 4

remove an at job

Answer 4

atrm 2

Question 5

Can’t open /run/atd.pid to signal atd. No atd running?

Answer 5

Install atd

Question 6

Schedule an AT job for 5 min from now

Answer 6

at now +5min

Question 7

teatime

Answer 7

4pm

Question 8

Execute command at teatime and put the job in a queue called g

Answer 8

at -q g teatime

Question 9

Cat an at job to the console

Answer 9

at -c 7

Question 10

In order, list the fields of a cron job

Answer 10

minute
hour
day of month
month
day of week
command

Question 11

In cron, what are values for day of the week?

Answer 11

0, 7 for Sunday
1 for Monday

Question 12

true command

Answer 12

do nothing and return success code 0

Question 13

false command

Answer 13

do nothing and return success code of 1

Question 14

List the cron tabs

Answer 14

crontab -l

Question 15

Install cron

Answer 15

dnf install cronie

Question 16

Create a cron job

Answer 16

crontab -e

Question 17

source fancy dot command

Answer 17

. ~/.bashrc

Question 18

Explain the crontab:

15,45  08,11,14   *  *  1-5  /bin/true

Answer 18

At 15 min or 45 min after 08, 11 or 1pm, any day of the month and for every month for working days, run /bin/true

Question 19

Explain the cron tab:

*/10 * * *  * /bin/true

Answer 19

Every tenth instance of every hour, every day of month, every month, every day of the week

Question 20

List the crontabs of student user

Answer 20

crontab -l -u student

Question 21

Where are cront tab installed

Answer 21

/var/spool/cron

Question 22

remove the crontab for student user

Answer 22

crontab -r -u student

Question 23

How many fields are used for user cron tabs?

Answer 23

6: min, hour, day of month, month, day of week command

Question 24

How many fields are used for system cron tabs?

Answer 24

7
additional field for the suer that the job is going to be executed as

Question 25

Where can I find information on the cron tab fileds?

Answer 25

/etc/crontab

Question 26

Where do I get help on system cron tabs?

Answer 26

man 5 crontab

Question 27

What is the cron drop in directory

Answer 27

/etc/cron.d

Question 28

Explain run‐parts command

Answer 28

command used to run all the executable scripts or programs in a directory in alphabetical order.

Question 29

Anacron

Answer 29

scheduling tasks to be executed periodicallyin systems not always on. Or when you do not care about precise executime time (daily, weekly, hourly).

Question 30

What are the anacron drop in directory

Answer 30

1) /etc/cron.hourly/, 2) /etc/cron.weekly/, 3) /etc/cron.daily/ 4) /etc/cron.monthy/

Question 31

what is anacrontab?

Answer 31

The anacrontab file in Linux is a configuration file for the Anacron service. It specifies how often Anacron runs certain tasks, much like a crontab file for Cron

Question 32

Explain nice command

Answer 32

nice is used to run a program with modified scheduling priority. By default, programs run with a normal priority level, but nice allows you to start a program with a lower priority, so that it uses less CPU resources.

Question 33

Setup anacron job to update locate database every hour

Answer 33

```echo 'updatedb' > /etc/cron.hourly/locate```

Question 34

List all systemd timer units

Answer 34

```systemctl list-units --type timer```

Question 35

Explain: w -h

Answer 35

w with no header

Question 36

How do you reload systemd after changing some units?

Answer 36

```systemctl daemon-reload```

Question 37

Enable a timer unit that was recently installed

Answer 37

systemctl enable --now sysstat-collect.timer

Question 38

Explain: ```crontab filename```

Answer 38

Replace all jobs with those read from filename. This command uses stdin input when no file is specified.

Question 39

How do you set who should receive the output of cron job execution?

Answer 39

Set MAILTO var in crontab file

Question 40

You want crond to run a command that requires data via stdin. How do you set it up?

Answer 40

Separate the command (inc its arguments) with the stdin data with percent sign

Question 41

A cron job writes to stdout. What happens with this output?

Answer 41

if MAILTO is configured it is sent to the specified user. Otherwise if it is a system job, it is sent to root. And else, it is send to the job owner.

Question 42

Instruct you shell to sleep until a file is created

Answer 42

```while ! test -f filename.txt; do sleep 1s; done```

Question 43

remove all cron jobs

Answer 43

crontab -r

Question 44

What do you put in following folders? ``` /etc/cron.daily/ /etc/cron.weekly/ /etc/cron.monthly/ ```

Answer 44

bash files with execute permission

Question 45

What are the fields of an anacron tab entry?

Answer 45

1) perdiod in days (1: for daily, 7 for weekly, @monthly) 2) period in minutes 3) job id 4) command

Question 46

Explain "Delay in minutes" in anacrontab

Answer 46

the time that the crond daemon must wait before it starts the job.

Question 47

Parameters that determine when anacron job will be run

Answer 47

1) RANDOM_DELAY 2) START_HOURS_RANGE 3) Delay in minutes

Question 48

Install sysstat package

Answer 48

dnf install sysstat

Question 49

What is sysstat

Answer 49

A unit that collects system stats regularly (by default 10 min)