RHCSA: Red Hat Certified System Administrator

Question 1

system activity reporter
cpu

Answer 1

sar -u

Question 2

sysstat
installation

Answer 2

INSTALL
yum -y install sysstat
systemctl start sysstat
systemctl enable sysstat

Question 3

shutdown in 10 min with msg

Answer 3

shutdown -h 10 “msg”

Question 4

shutdown -h 10: when no login possible

Answer 4

5 min before power off

Question 5

prompt every time for pw

Answer 5

sudo visudo
Defaults timestamp_timeout=0

Question 6

grub: enter recovery mode on boot

Answer 6

ESC grub
e to edit
line ‘linux16 …’ goto end
append systemd.unit=rescue.target
CTRL+x

Question 7

tar
archive the ceph/ directory with default settings

Answer 7

tar -cvf ceph.tar ceph

Question 8

grub: set passwd

Answer 8

GRUB PASSWORD
[root@muc-nb-gludwig]~# cp /etc/grub.d/01_users .
vi 01_users
#!/bin/sh -e
cat << EOF
set superusers=”gunnar”
password gunnar L1nux
EOF
this user doesn’t relate to the users on the OS
grub2-mkconfig -o /boot/grub2/grub.cfg

grub2-mkpassword-pbkdf2
#!/bin/sh -e
cat << EOF
set superusers=”gunnar”
password_pbkdf2 gunnar new_hashed_password
EOF
grub2-mkconfig -o /boot/grub2/grub.cfg

ACHTUNG! us keyboard is set in grub!

Question 9

grub2: enable recovery mode

Answer 9

CENTOS7 RECOVERY MODE
sudo vi /etc/default/grub
GRUB_DISABLE_RECOVERY=”false”
grub2-mkconfig -o /boot/grub2/grub.cfg

Question 10

Report virtual memory statistics
every 5 sec three times in MB

Answer 10

vmstat 5 3 -S M

Question 11

terminate a process
brute force and can leave orphaned processes

Answer 11

kill -9 | -kill | -sigkill PID

Question 12

lost passwd

Answer 12

CENTOS 7 LOST PASSWORD
ESC grub
e to edit
line ‘linux16 …’ goto end
remove ‘rhgd quite’
add ‘rd.break enforcing=0’
CTRL+x
(it stopps after completing the ramdisk phase)
switch_root:/# mount -o remount,rw /sysroot; chroot /sysroot
sh-4.3$ passwd; exit
switch_root:/# mount -o remount,ro /sysroot; exit (boot process is then continued)
login as root
restorecon /etc/shadow
setenforce 1

Question 13

processes bound to port

Answer 13

sudo yum install net-tools 
sudo netstat -tulpn | grep :80 
# sudo yum install lsof 
sudo lsof -i :80 
sudo lsof -i TCP:80 
# sudo yum install psmisc 
fuser 80/tcp

Question 14

shell variable
current process

Answer 14

$$

Question 15

run a program with modified scheduling priority

Answer 15

nice

Question 16

write / wall

Answer 16

write
wall
mesg y|n

Question 17

run level

Answer 17

who -r
runlevel
sudo systemctl get-default
systemctl isolate multi-user.target # stops everything what is not allowed to run in that level, but not set permanently
systemctl isolate rescue.target # single user mode

Question 18

nmcli

Answer 18

nmcli conn show
nmcli conn up

Question 19

cpio

Answer 19

find ceph -name ‘*.sh’ | cpio -o > ceph.cpio
find ceph -name ‘*.sh’ | cpio -o -H ustar > ceph1.cpio

mkdir ceph1
cd ceph1
cpio -id < ../ceph1.cpio

*NOTE* this tool is obsolete and if used it should use ustar:
cpio -o -H ustar

Question 20

network scripts

Answer 20

/etc/sysconfig/network-scripts

Question 21

grubby

Answer 21

grubby –default-kernel
grubby –set-default /boot/vmlinuz-4.18.0-240.1.1.el8_3.x86_64
grubby –info=ALL
grubby –info /boot/vmlinuz-4.18.0-240.1.1.el8_3.x86_64
grubby –remove-args=”rhgb quiet” –update-kernel /boot/vmlinuz-4.18.0-193.28.1.el8_2.x86_64

Question 22

grub: re-install

Answer 22

BIOS BASED MACHINE
grub2-install /dev/sda
EFI BASED MACHINE
yum reinstall grub2-efi shim

Question 23

system activity reporter
memory

Answer 23

sar -r

Question 24

system activity reporter
disk

Answer 24

sar -b

Question 25

system activity reporter network

Answer 25

sar -n DEV

Question 26

system activity reporter load avg

Answer 26

sar -q

Question 27

system activity reporter log storage

Answer 27

/var/log/sa/

Question 28

system activity reporter query log with start and end time

Answer 28

sar -s 14:50:00 -e 15:10:00 -f /var/log/sa/sa15

Question 29

sysstat config files

Answer 29

cat /etc/cron.d/sysstat cat /etc/sysconfig/sysstat

Question 30

Report Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions

Answer 30

iostat

Question 31

iostat for cpu human readable

Answer 31

iostat -ch

Question 32

iostat for disk human readable

Answer 32

iostat -dh

Question 33

iostat for disk in mega byte

Answer 33

iostat -m

Question 34

iostat for cpu human readable every five seconds five times

Answer 34

iostat 5 3 -ch

Question 35

Report statistics for Linux tasks

Answer 35

pidstat

Question 36

Report statistics for Linux tasks every five seconds three times for the current process

Answer 36

pidstat -p $$ 5 3

Question 37

Report statistics for Linux tasks every five seconds three times for gedit

Answer 37

pidstat -p $(pgrep gedit) 5 3

Question 38

Report processors related statistics for all processors

Answer 38

mpstat -P ALL

Question 39

Report processors related statistics for processor 1 every five seconds three times

Answer 39

mpstat -P 1 5 3

Question 40

tar archive and compress the ceph/ directory as gzip

Answer 40

tar -cvzf ceph.tar.gz ceph

Question 41

tar archive and compress the ceph/ directory as bzip2

Answer 41

tar -cvjf ceph.tar.bz2 ceph

Question 42

tar unpack the gz archive into tmp/

Answer 42

tar -C ~/tmp -xzf data\_flow.tar.gz

Question 43

tar list content of archive

Answer 43

tar -tvf ceph.tar

Question 44

tar incremental backup

Answer 44

tar -cvf my0.tar -g my.snar ceph/ tar -cvf my1.tar -g my.snar ceph/

Question 45

tar incremental restore

Answer 45

tar -xvf my0.tar -g /dev/null tar -xvf my1.tar -g /dev/null

Question 46

Report virtual memory statistics summarize disk statistics

Answer 46

vmstat -D

Question 47

Report virtual memory statistics disk statistics

Answer 47

vmstat -d

Question 48

Report virtual memory statistics event counter statistics

Answer 48

vmstat -s

Question 49

terminate a process allow the process to clean up behind itself

Answer 49

kill -15 | -term | -sigterm PID

Question 50

change and print terminal line settings print all current settings in human-readable form

Answer 50

stty -a

Question 51

look up process based on name find 'edit' like processes list PID and process name

Answer 51

pgrep edit -l

Question 52

look up process based on name find 'edit' like processes list PID and full command line

Answer 52

pgrep edit -a

Question 53

look up process based on name find 'edit' like processes use full process name to match

Answer 53

pgrep edit -f

Question 54

report a snapshot of the ssh processes extra full based on the name

Answer 54

ps -F -p $(pgrep ssh -f)

Question 55

kill processes based on name

Answer 55

pkill proc\_name

Question 56

proc details of current process

Answer 56

cd /proc/$$

Question 57

list all available runlevels

Answer 57

systemctl list-units --type=target

Question 58

set the multi-user.target

Answer 58

systemctl set-default multi-user.target reboot