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Rhcsa > Deploy, configure, and maintain systems > Flashcards

Deploy, configure, and maintain systems Flashcards

1
Q

networking dynamically(from DHCP)

A 
#cat /etc/sysconfig/network-cripts/ifcfg-eth1
DEVICE=eth1
HWADDR=[Mac Address]
TYPE=ethernet
UUID=[uuid number(hex)]
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=dhcp
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2
Q

Networking statically

A 
-edit file /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE="eth1"
BOOTPROTO="static"
DNS1="10.1.1.1"
GATEWAY="10.1.1.1"
HWADDR=[MAC Address]
IPADDR="10.1.1.3"
NETMASK="255.255.255.0"
IPV6INIT="yes"
NM_CONTROLLED="yes"
ONBOOT="yes"
TYPE="Ethernet"
UUID="[UUID hex number]"
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3
Q

after making changes to eth files

A 
#ifdown eth1
#ifup eth1
or
#service network restart
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4
Q

Primary network configuration files

A

/etc/hosts
/etc/resolv.conf
/etc/sysconfig/network
/etc/sysconfig/network-scripts/ifcfg-

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5
Q

Cron VS at

A

Cron is used to schedule recurring task while at is used to schedule a task to run at a particular time

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6
Q

Setting up a cron

A

chkconfig –list crond make sure that crond is set to boot

# service crond status check that crond is started
# cat /etc/crontab see rule example of job definition
* * * * *
1st star is for min(0-59)
2nd star is for hours(0-23)
3rd star is for day (1-31)
4th star is for month(1-12)
5th star is for day of the week(Sunday = 0 or 7, 0-6 Sunday-Saturday)

Review
#ls /var/spool/cron
#cat /var/spool/cron/root
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7
Q

Cron jobs that run periodically

A 
These jobs are stored and run periodically
# /etc/cron.daily
# /etc/cron.weekly
# /etc/cron.hourly
# /etc/cron.monthly
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8
Q

List crontab

A 
#crontab -l      list crontab as owner
#crontab -l -u user1    list crontab as root for user1
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9
Q

edit crontab

A 
#crontab -e     edit crontab for current user
# crontab -e -u user1   edit crontab for user1
only root can edit other user's crontab
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10
Q

/etc/cron.deny and /etc/cron.allow

A

add user to /etc/cron.deny or /etc/cron.allow to deny or allow them to be able to create cron jobs

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11
Q

Setting up at

A 
#service atd status     check that the atd service has started
# chkconfig --list atd    make sure it's set to start at boot
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12
Q

List of commands for at

A 
#at -f file.sh now+2minutes    sets a job to run in 2 mins
# atq    jobs that are submitted
# atrm 3   remove a job(enter job number)
#at -f some.sh 12pm tomorrow   run at 12PM tomorrow
#ls /var/spool/at   where the scrip for scheduled jobs are
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13
Q

Kickstart

A

-After an install a ks file is automatically created and stored in /root/anaconda-ks.cfg
- You can create a ks file by hand or you can use the system kickstart utility located here:
Applications -> System tools -> kickstart (it’s not installed by default)
- in the kickstart file, the lines that starts with”@” means a group package to be installed. The lines that starts with “-“ means to exclue those packages from being installed.

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14
Q

Installing from a KS in an NFS partition

A
  • first boot from the boot cd. Then press the ESC key
  • at the boot prompt type(press Enter afterward)
    boot: linus ks=nfs:IP:/srv/nfs/ks.cfg
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15
Q

Installing from a KS in an FTP or http location

A

While still booting from an actual install cd, you could add the location of the ks to an ftp or http server, and add such entry in the KS file:
usr –url=http://ip/rhel6
-After booting from the DVD install, press the tab key, then enter:
> vmlinuz initrd = initrd.img ks=http://ip/rhel/ks.cfg ksdevice=eth0

or
> vmlinuz initrd = initrd.img asknetwork ks=http://your.web.com/rhel6.cfg ksdevice=eth0

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16
Q

Kernel boot options:

A
  • linux ks = ftp://host/ks.cfg
  • linux ks = http://host/ks.cfg
  • linux ks = nfs:host:/ks.cfg
  • linux ks=hd:/dev/dir/ks.cfg
  • linux ks=file:/dev/dir/ks.cfg
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17
Q

NTP

A

You can syncronize the system clock with a remote server over the network Time Protocol(NTP). for the one-time synchronication only use the ntpdate command

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18
Q

the ntpdate command

A

1- first check whether the selected NTP server is accessible
#ntpdate -q server-address
2- run the command followed by one or more server addresses
#ntpdate server_address ….
enable running the ntpdate at boot time
#chkconfig ntpdate on

19
Q

Note if the synchronization with the time server at boot time keeps failing

A

You can find a relevant error message in the /var/log/boot.log. Then try to add the following line to /etc/sysconfig/network
NETWORKINGWAIT=1

20
Q

Best to set the ntpd daemon

A

The most convenient way is to set the netpd daemon to synchronize the time at boot time automatically
1. Open the NTP configuration file /etc/ntp.conf
2. add or edit the list of public NTP servers
server 0 rhel.pool.ntp.org iburst
-The iburst directive is to speed up the initial synchronization as of redhat 6.5, it is added by default.
3. In the same file, set the proper permissions giving unrestricted access to localhost only
restrict 127.0.0.1
restrict 6::1
4. save all changes, exit and restart the NTP daemon
#service ntpd restart
5 make sure that ntp is started at boot time
#chkconfig ntpd on

Note, if you are setting up the NTP server for others to access, remember to enable port 123 in the firewall.

21
Q

Yum repos

A
  • yum repos are located in /etc/yum.repos.d
  • all repository should end with .repo
  • no two repository can have the same repository ID
22
Q

Example of a repo file

A 
[localnet]
name = local network yum repo
baseurl = ftp://192.168.75.132/pub/
enabled=1
gpgcheck=0
gpgkey=file:///etc/......

review man yum.conf

23
Q

To register for red hat subscription

A

rhn_register then follow the instructions

24
Q

Setting up a local repo with a disk

A
  • first mount the disk
    -copy the packages from Packages into another directory
    -next install the package createrepo
  • once installed add into the directory and run
    # createrepo
    -Then create a file in /etc/yum.repos.d/ similar to
    # vi mylocal.repo
    [mylocal]
    name=mylocal
    baseurl=file:///directory/path/to/repo
    enabled=1
    gpgcheck=0
25
Q

To test for a specific package

A

yum list httpd

26
Q

Install and update software packages using rpm

A 
#rpm -ivh mypackage.rpm
#rpm -Uvh mypackage.rpm
27
Q

How to import the gpg key of repository

A

rpm –import gpgkey

28
Q

to see a list of repos

A

yum repolist

29
Q

installing and update via yum

A 
#yum install vsftp
#yum update vsftp
30
Q

Get kernel current version

A

uname -r

31
Q

kernel details

A
  • better to install a new kernel than to upgrade existing kernel
  • /boot/grub/grub.conf boot process (bootloader) uses this file
  • to know which kernel to booth with, the default is set to 0
  • To install kernel
    #yum install kernel
    #rpm -ivh kernel.rpm do not use -U
- not recommended how to update kernel
#yum upgrade kernel
#rpm -Uvh kernel.rpm
32
Q

Modify the system bootloader

A

-Edit the /boot/grub/grub.conf

What happens when a system boot
BIOS-> BootLoader(GRUB)(/boot) -> kernel(vmlinuz) -> mount file system “/” (read-only) -> /sbin/init

33
Q

to check which parameters has been passed in during boot

A

cat /proc/cmdline

34
Q

to add/pass parameter to the kernel

A

you need to edit /boot/grub/grub.con

35
Q

example of parameter that can be added

A

Console=ttyS0

36
Q

To setup password protect at Grub

A 
-Generate hash key
#grup-md5-crypt
password:
  • copy the hash key to /boot/grub/grub.conf
  • restart server for changes to take effect
  • test by trying to access grub
37
Q

To configure network services to start automatically at boot (for example httpd), type:

A

systemctl enable httpd

38
Q

To check the configuration, type:

A

systemctl is-enabled httpd

39
Q

To configure a system to boot into multi-user level without graphical interface, type:

A

systemctl set-default multi-user.target

40
Q

To configure a system to boot into multi-user level with graphical interface, type:

A

systemctl set-default graphical.target

41
Q

To check the current configuration, type:

A 
# systemctl get-default
multi-user.target
42
Q

To create a VM called postfix.example.com (here with an IP address of 192.168.1.10, a gateway in 192.168.1.1, a DNS server in 192.168.1.1, a repository server in 192.168.1.5, Pass1234 as a password, and a total disk size of 6GB), create the file /var/www/html/conf/ks_postfix.cfg and paste the following lines:

A

keyboard –vckeymap=us –xlayouts=’us’
lang en_US.UTF-8
network –device=eth0 –bootproto=static –ip=192.168.1.10 –netmask=255.255.255.0 –gateway=192.168.1.1 –nameserver=192.168.1.1 –activate –ipv6=auto
network –hostname=postfix.example.com
rootpw Pass1234
timezone America/Los_Angeles –isUtc
bootloader –location=mbr –boot-drive=vda
clearpart –all –initlabel –drives=vda
ignoredisk –only-use=vda
part pv.9 –fstype=”lvmpv” –ondisk=vda –size=5000
part /boot –fstype=”ext4” –ondisk=vda –size=500
volgroup rhel –pesize=4096 pv.9
logvol swap –fstype=”swap” –size=500 –name=swap –vgname=rhel
logvol / –fstype=”ext4” –size=3072 –name=root –vgname=rhel

%packages
@base
@core

%end
reboot

Then, run the following command:
# /bin/virt-install \
--virt-type kvm \
--name=postfix.example.com \
--disk path=/var/lib/libvirt/images/postfix.example.com.img,size=6 \
--ram=1024 \
--vcpus=1 \
--os-variant=rhel7 \
--accelerate \
--graphics vnc \
-v -l http://192.168.1.5/repo/CentOS/7/os/x86_64/ \
--network bridge:br0 \
-x ks=http://192.168.1.5/conf/ks_postfix.cfg

Note1: http in the previous command can be replaced with nfs, ftp, etc.
Note2: If you get this message “ERROR internal error: process exited while connecting to monitor: qemu-kvm: -chardev pty,id=charserial0: Failed to create chardev“, follow this thread.
Replace “devpts /dev/pts devpts defaults 0 0” with “devpts /dev/pts devpts gid=5,mode=620 0 0” in the /etc/fstab file of the KVM host.

43
Q

Configure a physical machine to host virtual guests.

A 
Update your system:
# yum update
Install the KVM packages:
# yum group install "Virtualization Host"
# yum install -y virt-install
# yum install -y virt-top
Start the libvirtd service:
# systemctl start libvirtd
Activate the Chronyd/NTP service at boot and start it:
# systemctl enable chronyd && systemctl start chronyd

Rhcsa (9 decks)

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