Scope: Distro-independent; applies to Debian-based and RHEL-based Linux distributions
Topics: os-release fields, scripting with os-release, uname, hostnamectl, release files, and verification.

1. Identify the Distribution with /etc/os-release#

/etc/os-release is the standard machine-readable identification file defined by the os-release specification. Shell scripts, provisioning tools, and package managers source it to detect the distribution. It is present on every current Debian-based and RHEL-based system.

Inspect the file:

cat /etc/os-release

Expected output on Ubuntu 24.04:

PRETTY_NAME="Ubuntu 24.04.1 LTS"
NAME="Ubuntu"
VERSION_ID="24.04"
VERSION="24.04.1 LTS (Noble Numbat)"
VERSION_CODENAME=noble
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=noble
LOGO=ubuntu-logo

Read the fields:

2. Use os-release in Scripts#

Source the file to load its fields as shell variables:

source /etc/os-release
echo "$ID" "$VERSION_ID"

Expected output:

ubuntu 24.04

Branch on the distribution in a script:

source /etc/os-release

if [ "$ID" = "ubuntu" ] || [ "$ID" = "debian" ]; then
    echo "Debian family: $PRETTY_NAME"
    apt update
elif [ "$ID" = "rocky" ] || [ "$ID" = "rhel" ]; then
    echo "RHEL family: $PRETTY_NAME"
    dnf check-update
else
    echo "Unsupported distribution: $ID"
fi

Check ID_LIKE for derivative distributions. Values such as ID_LIKE=debian on Ubuntu or ID_LIKE="rhel centos fedora" on Rocky Linux identify the upstream family, so a script can match the family instead of every derivative:

source /etc/os-release
case " $ID_LIKE " in
    *debian*) echo "Debian-based" ;;
    *rhel*)   echo "RHEL-based" ;;
    *)        echo "Unknown family" ;;
esac

3. Inspect the Kernel with uname#

Display all kernel and hardware information:

uname -a

Expected output:

Linux srv01 6.1.0-18-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.76-1 (2024-02-01) x86_64 GNU/Linux

Query individual fields:

uname -s
uname -r
uname -m
uname -n
uname -v

Options:

• -s: Kernel name, Linux.
• -r: Kernel release, for example 6.1.0-18-amd64. Use this for module and driver compatibility checks.
• -m: Hardware architecture, for example x86_64 or aarch64.
• -n: Network hostname. Prefer hostnamectl for hostname management.
• -v: Kernel build version string, including the build compiler and date.

4. Inspect the Hostname with hostnamectl#

A systemd-based system maintains three hostname values:

• Static: The configured hostname stored in /etc/hostname. Set by the administrator and applied at boot.
• Pretty: A free-form display name that may contain spaces and mixed case, shown in desktop environments.
• Transient: A temporary hostname set at runtime, for example by DHCP. It falls back to the static hostname when not supplied.

Display the current host status:

hostnamectl

Expected output:

 Static hostname: srv01
       Icon name: computer-vm
         Chassis: vm 🖴
Machine ID: 8f4a2b1c9d3e4f5a6b7c8d9e0f1a2b3c
       Boot ID: 1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d
Virtualization: kvm
Operating System: Ubuntu 24.04.1 LTS
          Kernel: Linux 6.8.0-45-generic
    Architecture: x86-64

Set the static hostname:

hostnamectl set-hostname <HOSTNAME>

Display only the static hostname:

hostnamectl --static

Options:

• set-hostname <HOSTNAME>: Sets the static hostname and applies it immediately.
• --static: Prints the static hostname only.
• --transient: Prints the transient hostname only.
• --pretty: Prints the pretty hostname only.
• --pretty, --static, or --transient combined with set-hostname: Sets only that hostname type.

5. Query Additional Release Files#

Inspect the login banner and hostname files:

cat /etc/issue
cat /etc/hostname

Check the distribution-specific version file. Debian-based systems provide /etc/debian_version:

cat /etc/debian_version

Expected output on Debian 12:

12.7

RHEL-based systems provide /etc/redhat-release:

cat /etc/redhat-release

Expected output on Rocky 9:

Rocky Linux release 9.4 (Blue Onyx)

Query the Linux Standard Base information when available:

lsb_release -a

Expected output:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 24.04.1 LTS
Release:        24.04
Codename:       noble

On Debian-based systems, lsb_release may require the lsb-release package:

apt install lsb-release

On RHEL-based systems it is available in the redhat-lsb-core package. When the tool is absent, /etc/os-release provides the same information without an extra dependency.

6. Verify the Collected Information#

Run the identification commands together and confirm that the values are consistent:

source /etc/os-release
echo "Distribution: $PRETTY_NAME"
echo "Kernel: $(uname -r)"
echo "Architecture: $(uname -m)"
hostnamectl --static

Expected output:

Distribution: Ubuntu 24.04.1 LTS
Kernel: 6.8.0-45-generic
Architecture: x86-64
srv01

Cross-check the results: the distribution name must match the release files, the architecture must match the installed package set, and the hostname must match /etc/hostname and the entry in /etc/hosts.

Part 3: Important Notes#

Debian vs RHEL os-release#

The same fields carry different values on each family:

Note that VERSION_CODENAME is not defined on RHEL-based systems, and ID_LIKE is empty on Debian itself because it is the upstream of its family. Scripts must handle missing fields gracefully.

Command Reference#

Security Guidelines#

• Replace placeholders such as <HOSTNAME> with actual values. Do not include the angle brackets in commands.
• Treat /etc/os-release as trustworthy metadata, not as security input. Do not use its values for access control or authorization decisions without additional verification.
• Do not rely on /etc/issue as an access control banner. Configure Banner /etc/issue.net in sshd_config and the corresponding PAM motd settings for pre-login legal notices.
• Prefer /etc/os-release over parsing lsb_release output in scripts. The file is always present and its fields follow a stable specification.
• Quote all variables sourced from /etc/os-release. Values such as PRETTY_NAME contain spaces and parentheses that break unquoted shell expansion.
• Match on ID or ID_LIKE instead of PRETTY_NAME or NAME. The human-readable fields change between releases and languages.
• Handle missing fields explicitly. VERSION_CODENAME and vendor-specific entries are optional, and set -u scripts must tolerate their absence.
• Use lowercase values for hostnamectl set-hostname and keep the hostname consistent with /etc/hosts to avoid unexpected resolution behavior.
• When logged in as root, the commands above generally do not require the sudo prefix.
• Re-verify system identification after major upgrades or migrations, since os-release contents and kernel versions change with the distribution release.