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Linux

Last modified by Jeff McDonald on 2024/03/30 18:54

Here are some notes for installing and configuring Oracle Linux.
None of them are particularly clever, I just often forget the exact commands.

Installation

Disable Predictive Network Interface Names

The WSC-ME does not support Predictable Network Interface Names.

To disable it, during installation, upon the initial install screen, press TAB, and add the following parameter to the boot parameters:

net.ifnames=0

Example:

> vmlinuz initrd=initrd.img inst.stage2=hd:LABEL=OL-7.2\x20Server.x86_64 rd.live.check quiet net.ifnames=0

Minimum Install

For Oracle products, always go with the minimum install (default).

Remember to:

Set the host name
Configure each network interface to "Automatically connect to this network when it is available"
Set the timezone and enable Network Time
Select the installation drive
Set root password

Network Installation

For Oracle 7: http://public-yum.oracle.com/repo/OracleLinux/OL7/latest/x86_64/

For Oracle 8: http://yum.oracle.com/repo/OracleLinux/OL8/baseos/latest/x86_64

Oracle YUM Server

Certain applications (like Docker) require authentication.

docker login container-registry.oracle.com

Screen Blanking

Screen blanking (on VMs) really annoys me. To turn of screen blanking from the console (not ssh):

setterm -powersave off -blank 0

Common User Modifications

The simplest way to give a user 'sudo' privileges is to add them to the 'wheel' group.

usermod -aG wheel <user>

Entering passwords every time I use 'sudo' annoys me.

Type 'visudo' to edit the 'sudoers' file. Comment out the regular line and uncomment the NOPASSWD line.

## Allows people in group wheel to run all commands
#%wheel ALL=(ALL) ALL
## Same thing without a password
%wheel ALL=(ALL) NOPASSWD: ALL

Typing a password when using SSH also annoys me. From your workstation, run the command:

ssh-copy-id <user>@<hostname>

If you like, you can disable passwords (in favor of security keys) by editing /etc/ssh/sshd_config.
Change PermitRootLogin and PasswordAuthentication.
Here's a quick command to do it:

sudo sed -i --follow-symlinks 's/#PermitRootLogin yes/PermitRootLogin no/g' /etc/ssh/sshd_config
sudo sed -i --follow-symlinks 's/^PasswordAuthentication yes$/PasswordAuthentication no/g' /etc/ssh/sshd_config

YUM

Before using 'yum', always run an update:

sudo yum -y update

Oracle comes with some interesting repositories. Take a look at "/etc/yum.repos.d" for a list of repositories.
To enable them, type:

sudo yum -y install yum-utils
sudo yum-config-manager --enable <repository>

Open VM Tools

If needed, install Open VM Tools.

sudo yum -y install open-vm-tools

SELinux

It must have a purpose, but I find it annoying. It can be disabled like this:

sudo setenforce 0
sudo sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux

Firewall

I also find the built-in firewall annoying.

To disable it:

sudo systemctl stop firewalld
sudo systemctl disable firewalld

However, if you would like to use it properly, here are some examples to give you ideas:

sudo firewall-cmd --add-port=1521/tcp --permanent
sudo firewall-cmd --add-port=5060/udp --permanent
sudo firewall-cmd --zone=public --permanent --add-service=http
sudo firewall-cmd --zone=public --permanent --add-service=https
sudo systemctl restart firewalld

Random Numbers

Headless servers have a hard time producing random numbers. This will slow WebLogic and other applications.
To check your entropy:

cat /proc/sys/kernel/random/entropy_avail

If the number is less than 1000, install 'haveged':

sudo yum-config-manager --add-repo https://yum.oracle.com/repo/OracleLinux/OL8/developer/EPEL/x86_64
sudo yum -y install haveged
sudo systemctl enable haveged.service
sudo systemctl start haveged

Kernel Parameter Tuning

Here's a quick way to tune kernel parameters:

yum -y install oracle-database-preinstall-19c

Wireshark

Getting this error?

libGL error: failed to load driver: swrast

Install drivers:

sudo dnf install -y mesa-dri-drivers