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RHCSA 7 C > 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-eno1
NAME=eno1
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-eno1
NAME="eno1"
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

systemctl restart network

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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

/etc/hosts

A

Purpose is to resolve host names that cannot be resolved any other way. It can also be used to resolve host names on small networks with no DNS server. This file should contain a line specifying the IP address of the loopback device(127.0.0.1) as localhost.domain

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6
Q

/etc/resolv.conf

A

This file specifies the IP addresses of DNS servers and the search domain. Unless configured to do otherwise, the network initialization scripts populate this file. Review man 5 resolv.conf

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7
Q

/etc/sysconfig/network

A

This file specifies routing and host information for all network interfaces. It is used to contain directives which are to have global effect and not to be interface specific

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8
Q

/etc/sysconfig/network-scripts/ifcfg-

A

for each network interface, there is a corresponding interface script

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9
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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10
Q

Setting up a cron

A

systemctl list-unit-files | grep crond

make sure that crond is set to boot
#systemctl status crond.service 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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11
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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12
Q

List crontab

A 
#crontab -l      list crontab as owner
#crontab -l -u user1    list crontab as root for user1
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13
Q

edit crontab

A 
#crontab -e     edit crontab for current user
# crontab -e -u user1   edit crontab for user1only root can edit other user's crontab
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14
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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15
Q

Setting up at

A 
#systemctl status atd.service     check that the atd service has started
# systemctl list-unit-files | grep atd
make sure it's set to start at boot
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16
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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17
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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18
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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19
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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20
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
21
Q

setup NTP service

A

NTP (Network Time Protocol) is a service to keep servers time synchronized.

Install the NTP package:
# yum install -y ntp
Activate the NTP service at boot:
# systemctl enable ntpd
Start the NTP service:
# systemctl start ntpd

The NTP configuration is in the /etc/ntp.conf file.

To get information about the time synchronization process, type:
# ntpq -p
To quickly synchronize a server, type:
# systemctl stop ntpd
# ntpdate pool.ntp.org
adjust time server 95.81.173.74 offset -0.005354 sec
# systemctl start ntpd
22
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
##systemctl enable ntpdate.service
23
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

24
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 serversserver 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 127.0.0.1restrict 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
#systemctl enable ntp.service
Note, if you are setting up the NTP server for others to access, remember to enable port 123 in the firewall.

25
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
26
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
27
Q

To register for red hat subscription

A

rhn_register then follow the instructions

28
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
  • Optionally, update the repository structure (if new packages have been added):
    # yum install -y createrepo
    # createrepo /repo
    -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
Clean up the yum cache:
# yum clean all
29
Q

rpm commands

A 
To install (-i) a new package (here httpd-2.2.15-29.el6.x86_64.rpm), type:
# rpm -ivh httpd-2.2.15-29.el6.x86_64.rpm
To upgrade (-U) an existing package (here httpd-2.2.15-29.el6.x86_64.rpm), type:
# rpm -Uvh httpd-2.2.15-29.el6.x86_64.rpm
To erase (-e) an existing package (here httpd-2.2.15-29.el6.x86_64), type:
# rpm -evh httpd-2.2.15-29.el6.x86_64
To get the list of all the installed packages, type:
# rpm -qa
To get some details about a package (here httpd-2.2.15-29.el6.x86_64), type:
# rpm -qi httpd-2.2.15-29.el6.x86_64
To get the package file list (here httpd-2.2.15-29.el6.x86_64), type:
# rpm -ql httpd-2.2.15-29.el6.x86_64
To get the list of all the modified files in the system, type:
# rpm -qVa
To get the change history of a package (here openssl), type:
# rpm -q --changelog openssl
import the gpg key of repository
#rpm --import gpgkey

Caution: If it is very useful to know the rpm command to query the system, it’s better not to use it to install a package:

rpm doesn’t check package dependencies, you’ll have to do it yourself or use yum.

30
Q

to see a list of repos

A 
#yum repolist
# yum repolist all
To get the list of the disabled repositories, type:
# yum repolist disabled
31
Q

Yum commands

A 
To install a new package (here httpd), type:
# yum install httpd
To remove an existing package (here httpd), type:
# yum remove httpd
To get some details about a package (here httpd), type:
# yum info httpd
To install a package group (here “Web Server”), type:
# yum groupinstall "Web Server"
To remove a package group (here “Web Server”), type:
# yum groupremove "Web Server"
To get the list of installed package groups, type:
# yum grouplist
To get some details about a package group (here “Web Server”), type:
# yum groupinfo "Web Server"
To define which package provides a specified file (here semanage), type:
# yum whatprovides */semanage
To search for a particular string (here seinfo), type:
# yum search seinfo
To update the current base of installed packages, type:
# yum update
To get the list of all the available packages, type:
# yum list
To get the list of all the installed packages, type:
# yum list installed
To display the list of all the available but not alerady installed packages, type:
# yum list available
To get the list of the available repository, type:
# yum repolist
To clean up the yum cache, type:
# yum clean all
To get the list of the dependencies associated with a package (here httpd), type:
# yum deplist httpd
32
Q

Get kernel current version

A

uname -r

33
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
34
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

35
Q

to check which parameters has been passed in during boot

A

cat /proc/cmdline

36
Q

to add/pass parameter to the kernel

A

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

37
Q

example of parameter that can be added

A

Console=ttyS0

38
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
39
Q

To permanently enable/disable a repository (here epel), type:

A 
# yum-config-manager --enable epel
# yum-config-manager --disable epel
40
Q

To temporary enable/disable a repository (here epel) in order to install a specific package (here Pound), type:

A 
# yum --enablerepo=epel install Pound
Note: Use the –disablerepo option to temporary disable a repository
41
Q

To configure an access to a remote repository, create the /etc/yum.repos.d/remote.repo file and add the following lines:

A

[base]
name=CentOS-$releasever - Base
baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
enabled=1

42
Q

Alternatively to NTP, you can install the new chrony service that is quicker to synchronize clocks in mobile and virtual systems.

A 
Install the chrony service:
# yum install -y chrony
Activate the chrony service at boot:
# systemctl enable chronyd
Start the chrony service:
# systemctl start chronyd

The Chrony configuration is in the /etc/chrony.conf file.

To get information about the main time reference, type:
# chronyc tracking

To get equivalent information to the ntpq command, type:

# chronyc sources -v
# chronyc sourcestats -v
To quickly synchronize a server, type:
# ntpdate pool.ntp.org

on master you must add the following into /etc/chrony.conf

# Allow NTP client access from local network.
allow 192.168.0.0/24

– copy the key file to the clients
– open up ntp service port firewall-cmd

On clients you must specify the following and disable “server” in /etc/chrony.conf

# Use Peer
peer 192.168.0.33
43
Q

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

A

systemctl enable httpd

To check the configuration, type:
# systemctl is-enabled httpd
44
Q

Configure systems to launch virtual machines at boot.

A

To launch a virtual machine called vm.example.com at boot, type the following command:

# virsh autostart vm.example.com
To disable this same launch at boot, type:
# virsh autostart vm.example.com --disable
To get the list of all the virtual machines, type:

virsh list –all

45
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.

46
Q

Configure a physical machine to host virtual guests.

A

Download the CentOS 7 distribution (see Software requirements) and install it with default configuration.

Choose a domain name (example.com strongly recommended), a host name (for example master.example.com) and an IP address compatible with your network environment (here 192.168.1.5, gateway is supposed to be 192.168.1.1).

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
47
Q

Configure systems to boot into a specific target automatically.

A 
To configure a system to boot into multi-user level without graphical interface, type:
# systemctl set-default multi-user.target
To configure a system to boot into multi-user level with graphical interface, type:
# systemctl set-default graphical.target
To check the current configuration, type:
# systemctl get-default
multi-user.target
48
Q

To set a service to start or stop on boot you can use systemctl like so:

A

systemctl enable sshd.service

Likewise, to make sure a service does not start on boot (or disable), you can use systemctl like so:

systemctl disable sshd.service

You can check if a service is enabled or disable by using the “status” option to systemctl like this:

systemctl status sshd.service

RHCSA 7 C (10 decks)

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