feat(machine): add OS and kernel version information to machine info, show in 'machine ls'

internal/machine/osinfo/osinfo.go

@@ -0,0 +1,104 @@
+// Package osinfo collects the host operating system information.
+package osinfo
+
+import (
+	"bufio"
+	"io"
+	"os"
+	"strings"
+)
+
+// Paths to the files describing the OS release. They are package variables so tests can override them.
+var (
+	osReleasePaths    = []string{"/etc/os-release", "/usr/lib/os-release"}
+	debianVersionPath = "/etc/debian_version"
+)
+
+// PrettyName returns a human-readable OS name and version derived from os-release, or an empty string
+// if it cannot be determined. For example, "Ubuntu 24.04.4 LTS" or "Debian 13.5".
+func PrettyName() string {
+	rel := readOSRelease()
+	if len(rel) == 0 {
+		return ""
+	}
+
+	// Debian's os-release only carries the major version (e.g. "13"), while /etc/debian_version
+	// holds the point release (e.g. "13.5"). Read it to report the precise version.
+	var debianVersion string
+	if rel["ID"] == "debian" {
+		if data, err := os.ReadFile(debianVersionPath); err == nil {
+			debianVersion = strings.TrimSpace(string(data))
+		}
+	}
+
+	return buildPrettyName(rel, debianVersion)
+}
+
+// readOSRelease reads the first available os-release file and parses it into a key-value map. It
+// returns an empty map if no file is found.
+func readOSRelease() map[string]string {
+	for _, path := range osReleasePaths {
+		f, err := os.Open(path)
+		if err != nil {
+			continue
+		}
+		rel := parseOSRelease(f)
+		f.Close()
+		return rel
+	}
+	return nil
+}
+
+// parseOSRelease parses an os-release file into a key-value map. Blank lines and comments are
+// skipped, and surrounding quotes are stripped from values.
+func parseOSRelease(r io.Reader) map[string]string {
+	rel := make(map[string]string)
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		key, value, ok := strings.Cut(line, "=")
+		if !ok {
+			continue
+		}
+		key = strings.TrimSpace(key)
+		value = strings.Trim(strings.TrimSpace(value), `"'`)
+		rel[key] = value
+	}
+	return rel
+}
+
+// buildPrettyName composes a human-readable OS name and version from the parsed os-release map and the
+// contents of /etc/debian_version (empty for non-Debian systems).
+func buildPrettyName(rel map[string]string, debianVersion string) string {
+	// Debian's PRETTY_NAME is verbose ("Debian GNU/Linux 13 (trixie)") and lacks the point release,
+	// so prefer the precise version or codename (unstable releases) from /etc/debian_version.
+	if rel["ID"] == "debian" {
+		return strings.Join([]string{"Debian", debianVersion}, " ")
+	}
+
+	// PRETTY_NAME is the vendor's human-readable string and already includes the point release on
+	// most distros (e.g. "Ubuntu 24.04.4 LTS").
+	if pretty := rel["PRETTY_NAME"]; pretty != "" {
+		return pretty
+	}
+
+	// Fall back to composing the name from the individual fields.
+	name := rel["NAME"]
+	if name == "" {
+		name = rel["ID"]
+	}
+	parts := make([]string, 0, 3)
+	if name != "" {
+		parts = append(parts, name)
+	}
+	if version := rel["VERSION_ID"]; version != "" {
+		parts = append(parts, version)
+	}
+	if codename := rel["VERSION_CODENAME"]; codename != "" {
+		parts = append(parts, "("+codename+")")
+	}
+	return strings.Join(parts, " ")
+}