version/distro: detect Ubuntu separately from Debianbradfitz/distro_ubuntu

(for an upcoming change where I wanted to easily distinguish these
two)

Change-Id: Icb6a0144275cc9bf8978a7cb96b601d516d8da46
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

2 files changed, 25 insertions, 1 deletions

diff --git a/version/distro/distro.go b/version/distro/distro.go
index 3b1d36378..ca7a761fa 100644
--- a/version/distro/distro.go
+++ b/version/distro/distro.go
@@ -10,13 +10,16 @@ import (
 	"runtime"
 	"strconv"
 
+	"go4.org/mem"
 	"tailscale.com/syncs"
+	"tailscale.com/util/lineread"
 )
 
 type Distro string
 
 const (
 	Debian    = Distro("debian")
+	Ubuntu    = Distro("ubuntu")
 	Arch      = Distro("arch")
 	Synology  = Distro("synology")
 	OpenWrt   = Distro("openwrt")
@@ -62,9 +65,20 @@ func linuxDistro() Distro {
 	case haveDir("/usr/syno"):
 		return Synology
 	case have("/usr/local/bin/freenas-debug"):
-		// TrueNAS Scale runs on debian
+		// TrueNAS Scale runs on debian so test for it before Debian.
 		return TrueNAS
 	case have("/etc/debian_version"):
+		// Ubuntu also has an /etc/debian_version file, so see if it's actually Ubuntu.
+		isUbuntu := false
+		lineread.File("/etc/os-release", func(line []byte) error {
+			if mem.HasPrefix(mem.B(line), mem.S("ID=ubuntu")) {
+				isUbuntu = true
+			}
+			return nil
+		})
+		if isUbuntu {
+			return Ubuntu
+		}
 		return Debian
 	case have("/etc/arch-release"):
 		return Arch
@@ -110,3 +124,8 @@ func DSMVersion() int {
 	v, _ := strconv.Atoi(os.Getenv("SYNOPKG_DSM_VERSION_MAJOR"))
 	return v
 }
+
+// LikeDebian reports whether d is Debian-derived.
+func (d Distro) LikeDebian() bool {
+	return d == Debian || d == Ubuntu
+}
diff --git a/version/distro/distro_test.go b/version/distro/distro_test.go
index bc4e8c5b4..1f91d97f2 100644
--- a/version/distro/distro_test.go
+++ b/version/distro/distro_test.go
@@ -14,3 +14,8 @@ func BenchmarkGet(b *testing.B) {
 	}
 	_ = d
 }
+
+func TestGet(t *testing.T) {
+	d := Get()
+	t.Logf("Get = %q", d)
+}