Day 1 - Installation Types and Preparation: Before You First Install Linux

📌 Key Takeaways

• Before installing, first check the architecture (x86_64/ARM) and hardware compatibility.
• Installation media come in four types: DVD, USB, network (PXE), and Live image. A Live image is for trying it out first without installing.
• Installation types split into server / desktop / minimal, and the rule for servers is usually to leave out the GUI.
• For beginner study, a virtual machine installation is the safest. You can roll back with snapshots.
• At the end of installation, you create the root password and a regular user account. Do everyday work as the regular user.

What to Check Before Installing

If the architecture doesn't match, the installation won't even start. 32-bit is written as i386/i686, and 64-bit as x86_64 (or amd64).

The Four Types of Installation Media

• The key point of a Live image is that "it doesn't write to the disk." When you power off, your work disappears.
• That's why it's also used to recover a system whose hard disk is broken.
• Most Live images also provide an "Install now" button.

Reading Image File Names

If you visit a distribution's site, there are several images even for the same version. The file name contains the version, architecture, and type.

• The same 64-bit PC is written x86_64 in the Red Hat family and amd64 in the Debian family. It's the same architecture with only the name differing.
• A network install image is small and easy to download, but if the internet drops during installation, it can't proceed.

Verifying the Downloaded Image and Writing It to USB

sha256sum Rocky-9.3-x86_64-minimal.iso     # Compute the hash — compare it with the CHECKSUM value on the site
lsblk                                      # Check what device name the USB got (e.g., sdb)
sudo dd if=Rocky-9.3-x86_64-minimal.iso of=/dev/sdb bs=4M status=progress
sync                                       # Write out whatever remains in the buffers

• The output of sha256sum is a single line: 64-digit hex file name. If even one character differs, the download was corrupted or tampered with, so download it again.
• In dd, if is the input file and of is the output target (output file).
• On Windows, programs like Rufus and balenaEtcher do the same job.

⚠️ Trap: In of=, write the whole disk /dev/sdb, not a partition like /dev/sdb1. And dd overwrites without asking — if you mistakenly write the device name as sda, the disk you're using now gets erased. Always check with lsblk first.

What PXE Needs to Work

PXE installation plugs no media into the computer, but instead needs preparation on the network side.

The Three Installation Types

   Minimal                Server                 Desktop
   ─────────────          ────────────           ────────────────
   Kernel + essential     Minimal + server       Server + X Window + apps
   tools only             daemons
   No GUI                 No GUI (recommended)   Has a GUI
   Lightest               For web/DB servers     For personal PCs
   Pick and install       Managed via remote     Used in front of
   what you want          access                 the screen

• There are two reasons not to put a GUI on a server.
  • It uses resources — there's no reason to spend memory and CPU on drawing a screen.
  • The attack surface widens — the more programs installed, the more vulnerabilities there are.
• This principle is called minimal installation.

On the actual installer screen, these three types appear as a menu for choosing a package bundle (environment). The 'Software Selection' item of the Red Hat-family installer is an example.

• Depending on what you picked, whether the first screen after boot is text or graphical differs (runlevels 3 and 5, which we cover on Day 4, are exactly this).
• Installing minimal and later adding only what you need with the package manager is easier and safer than installing a lot and stripping it down.

Where to Install

For study purposes, we strongly recommend a virtual machine. Even if you set up partitions wrong, you can just roll back with a snapshot, and you can repeat the installation process as many times as you like. VirtualBox, VMware, or KVM — any is fine.

To use a virtual machine, the CPU's virtualization feature must be on. On a computer that already runs Linux, check like this.

grep -E -c 'vmx|svm' /proc/cpuinfo     # If 0, it's unsupported or turned off in the firmware settings
lscpu | grep -i virtualization

$ lscpu | grep -i virtualization
Virtualization:                  VT-x

• Among the flags in /proc/cpuinfo, vmx is Intel VT-x and svm is AMD-V.
• Even if the CPU supports it, it's often turned off in the BIOS/UEFI settings. If a virtual machine can't start a 64-bit image, look here first.

The Order of the Installation Process

Most distributions follow this flow.

1. Start up from the boot media
        ▼
2. Choose language · keyboard · time zone
        ▼
3. Set up disk partitions          ◄── The most important and hardest-to-undo step
        ▼
4. Set network · hostname
        ▼
5. Choose the packages (software) to install
        ▼
6. Create root password · regular user account
        ▼
7. Installation proceeds → reboot

• Step 3 is the core of this week, so we spend all of tomorrow on it.
• Do everyday work as the regular user created in step 6, and raise privileges only when administrative work is needed. Staying logged in as root all the time is a shortcut to accidents.

Installer Names and Automated Installation

The installer that guides you through the sequence above on screen also has a name, and it differs by family.

• Automated installation means writing in advance, in a single file, the answers a person would pick in steps 2 to 6 and handing it to the installer. Combined with PXE, you can install dozens of machines without touching them.
• On the Red Hat family, when installation finishes, what you chose in this installation is left in Kickstart format at /root/anaconda-ks.cfg. You use it as a model when building another server with the same configuration.

How the root Account Is Handled Differs by Distribution

• That's why on Ubuntu, typing su - doesn't get you in, because there's no root password. You use the sudo command form.
• Either way, the principle is the same — use a regular user normally, and raise privileges only when needed.

First Checks After Installation

uname -r                 # Kernel version
cat /etc/*-release       # Distribution name and version
df -h                    # Whether partitions were set up as intended
free -h                  # Memory and swap
ip addr                  # Whether the network is up

$ free -h
               total        used        free      shared  buff/cache   available
Mem:           3.8Gi       412Mi       2.9Gi       8.0Mi       520Mi       3.2Gi
Swap:          2.0Gi          0B       2.0Gi
 
$ hostnamectl
 Static hostname: web01
Operating System: Rocky Linux 9.3 (Blue Onyx)
          Kernel: Linux 5.14.0-362.8.1.el9_3.x86_64
    Architecture: x86-64

• The hostname can be changed after installation with hostnamectl set-hostname name. The same goes for language, time zone, and packages. Practically the only thing you can't change after installation is the partitions, so that step is the most important.

Commonly Mistaken Points

1. "A Live image isn't for installing" → It means you can also use it without installing. Most include an install function as well.
2. "amd64 is only for AMD CPUs" → It's a name also used for Intel 64-bit CPUs. It's the same as x86_64.
3. "On servers you install a GUI for easy management" → The principle is the opposite. Install minimal and manage remotely.
4. "PXE is a way of booting from USB" → It's a way of booting over the network. It needs DHCP and TFTP servers.
5. "Dual boot uses two OSes at the same time" → You pick one at boot time to use. Using them at the same time is a virtual machine.

Tomorrow we cover the hardest step of the installation process — how to divide up the partitions.

📖 Glossary

• Architecture : The CPU type and its instruction set. x86_64, ARM, etc. The image must match it.
• ISO image : The contents of an optical disc packed into a single file. The standard form of installation media.
• Live image : A distribution that runs straight from memory without being installed on disk. For trying out and recovery.
• PXE : A way of booting over the network and installing. Used when installing many machines at once.
• Minimal installation : Installing only what is absolutely necessary. Its goals are saving resources and strengthening security.
• Dual boot : Installing two operating systems on one computer and choosing between them at boot time.
• Snapshot : A feature that saves a virtual machine's state at a certain point in time and rolls back to it.
• Hostname : The name by which the computer is called on the network.