System Details

Kernel version, uptime, and other information to characterize the system.

Commands

uname -a	Prints kernel name, release, and version.
uname -r	Prints just the kernel release.
uname -v	Prints the kernel version.
uname -o	Prints the operating system.
uname -i	Prints the hardware platform.
cat /etc/*rel*	Prints information regarding the OS.
cat /etc/issue	Displays distribution-specific information.
cat /etc/*-release	Displays distribution information.
cat /etc/os-release	Displays operating system details.
uptime	Displays system uptime.
lsb_release -a	Shows Linux distribution information.
hostnamectl	Displays the system hostname and other system information (systemd systems).

File Locations

/etc/os-release or /usr/lib/os-release	On modern Linux distributions adhering to the Freedesktop.org Desktop Entry Specification, contains OS and version information. Provides structured data including operating system name, version, ID, and more.
/etc/lsb-release	Stores OS and version information on some distributions like Ubuntu. Contains distribution ID, release number, and description.
/etc/redhat-release	Typically found on Red Hat-based distributions such as Red Hat Enterprise Linux (RHEL) and CentOS. Contains distribution name and version.
/etc/debian_version	Stores the Debian release version on Debian-based distributions like Debian and Ubuntu.
/etc/issue or /etc/issue.net	May contain a message or banner with OS information, typically displayed during system startup or login.
/proc/version	Contains information about the kernel version and build date. Often used to determine the kernel version.
/etc/hostname	Stores the system hostname on some Unix systems.
/etc/*-release	Some distributions may have release-specific files in the /etc/ directory, such as /etc/centos-release or /etc/centos-release-upstream on CentOS.
ls /etc/release	Lists files related to release information in the /etc/ directory.