The document discusses the importance of understanding Linux systems for effectively reading technical documentation. It provides essential command line configurations, kernel module management, and settings for virtualization in Red Hat Enterprise Linux. Key commands for system tuning, file management, and the use of systemd scripts are also highlighted.

1. Importance of Linux System
Fundamental In Technical
Documentation Reading
by
netman<netman@study-area.org>
August 2016

2. The Sample Document
https://access.redhat.com/documentation/en-
US/Red_Hat_Enterprise_Linux/7/pdf/Virtualization_Tuning_and_Optimization_Guide/R
ed_Hat_Enterprise_Linux-7-Virtualization_Tuning_and_Optimization_Guide-en-US.pdf

3. The Basic Requirement
English reading Google searching+

4. Command line & Quoting
Improper line ending
perf kvm --host --guest --guestmodules=guest-modules report -i
perf.data.kvm --force > analyze
Should be:
perf kvm --host --guest --guestmodules=guest-modules report -i perf.data.kvm
--force > analyze
Or:

5. Configuration of sysctl
echo “net.ipv4.conf.all.arp_filter=1” >> /etc/sysctl.conf
sysctl -p
It means:

6. Kernel module management
echo “options vhost_net experimental_zcopytx=1”
> /etc/modprode.d/vhost_net.conf
modprobe –r vhost_net
modprobe vhost_net
Actually you should do:

7. Configuration file path
You have to know about:
• The guest xml path:
/etc/libvirt/qemu/guest_name.xml
OR
• The command to edit guest xml:
virsh edit guest_name
Substitute to a number!

8. Try & Error
virsh memtune virtual_machine --hard-limit size
It is wrong!!
It should be:

9. Using systemd
Using echo command to change /sys settings will be lost after reboot!
Solutions:
• Put the commands into /etc/rc.local
OR
• Create a systemd script :
vi /etc/systemd/system/set_transparent_hugepages.service
[Unit]
Description=Disable transparent hugepages
After=multi-user.target
[Service]
ExecStart=/usr/bin/bash -c 'echo never > /sys/kernel/mm/transparent_hugepage/enabled'
[Install]
WantedBy=graphical.target
systemctl enable set_transparent_hugepages.service

10. Vi/Vim Editing
It requires you using vi or vim!

11. Grub configuration
It’s talking about modifying kernel options in GRUB:
vi /etc/default/grub
GRUB_CMDLINE_LINUX=“… default_hugepagesz=1G hugepagesz=1G hugepages=4 hugepagesz=2M hugepages=1024"
grub2-mkconfig -o /boot/grub2/grub.cfg

12. Using yum
yum list '*numa*'
yum install numactl
Command not found!!
You must install it first:

13. Using locate
It doesn’t show you the full path!
You have to find it out:

14. Many more…

15. Thank you!