New: Musl (alpine linux) compatibility

src/Directory.Build.props

@@ -6,8 +6,8 @@
 
     <PlatformTarget>AnyCPU</PlatformTarget>
     <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
-    <RuntimeIdentifiers>win-x64;osx-x64;linux-x64;linux-arm;linux-arm64</RuntimeIdentifiers>
-    <ExcludedRuntimeFrameworkPairs>win-x64:net462;osx-x64:net462;linux-arm:net462;linux-arm64:net462</ExcludedRuntimeFrameworkPairs>
+    <RuntimeIdentifiers>win-x64;osx-x64;linux-x64;linux-musl-x64;linux-arm;linux-arm64;linux-musl-arm64</RuntimeIdentifiers>
+    <ExcludedRuntimeFrameworkPairs>win-x64:net462;osx-x64:net462;linux-arm:net462;linux-arm64:net462;linux-musl-x64:net462;linux-musl-arm64:net462</ExcludedRuntimeFrameworkPairs>
 
     <LidarrRootDir>$(MSBuildThisFileDirectory)..\</LidarrRootDir>
 

src/NzbDrone.Common/EnvironmentInfo/OsInfo.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using NLog;
@@ -11,7 +12,7 @@ namespace NzbDrone.Common.EnvironmentInfo
         public static Os Os { get; }
 
         public static bool IsNotWindows => !IsWindows;
-        public static bool IsLinux => Os == Os.Linux;
+        public static bool IsLinux => Os == Os.Linux || Os == Os.LinuxMusl || Os == Os.Bsd;
         public static bool IsOsx => Os == Os.Osx;
         public static bool IsWindows => Os == Os.Windows;
 
@@ -37,18 +38,7 @@ namespace NzbDrone.Common.EnvironmentInfo
                 case PlatformID.MacOSX:
                 case PlatformID.Unix:
                     {
-                        // Sometimes Mac OS reports itself as Unix
-                        if (Directory.Exists("/System/Library/CoreServices/") &&
-                            (File.Exists("/System/Library/CoreServices/SystemVersion.plist") ||
-                            File.Exists("/System/Library/CoreServices/ServerVersion.plist")))
-                        {
-                            Os = Os.Osx;
-                        }
-                        else
-                        {
-                            Os = Os.Linux;
-                        }
-
+                        Os = GetPosixFlavour();
                         break;
                     }
             }
@@ -92,6 +82,48 @@ namespace NzbDrone.Common.EnvironmentInfo
                 IsDocker = true;
             }
         }
+
+        private static Os GetPosixFlavour()
+        {
+            var output = RunAndCapture("uname", "-s");
+
+            if (output.StartsWith("Darwin"))
+            {
+                return Os.Osx;
+            }
+            else if (output.Contains("BSD"))
+            {
+                return Os.Bsd;
+            }
+            else
+            {
+                return IsMusl() ? Os.LinuxMusl : Os.Linux;
+            }
+        }
+
+        private static bool IsMusl()
+        {
+            var output = RunAndCapture("ldd", "/bin/ls");
+            return output.Contains("libc.musl");
+        }
+
+        private static string RunAndCapture(string filename, string args)
+        {
+            Process p = new Process();
+            p.StartInfo.FileName = filename;
+            p.StartInfo.Arguments = args;
+            p.StartInfo.UseShellExecute = false;
+            p.StartInfo.CreateNoWindow = true;
+            p.StartInfo.RedirectStandardOutput = true;
+
+            p.Start();
+
+            // To avoid deadlocks, always read the output stream first and then wait.
+            string output = p.StandardOutput.ReadToEnd();
+            p.WaitForExit(1000);
+
+            return output;
+        }
     }
 
     public interface IOsInfo
@@ -107,6 +139,8 @@ namespace NzbDrone.Common.EnvironmentInfo
     {
         Windows,
         Linux,
-        Osx
+        Osx,
+        LinuxMusl,
+        Bsd
     }
 }

src/NzbDrone.Mono.Test/Lidarr.Mono.Test.csproj

@@ -16,7 +16,7 @@
        See https://github.com/xamarin/XamarinComponents/issues/282
   -->
   <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
-    <PackageReference Include="Mono.Posix.NETStandard" Version="1.0.0" />
+    <PackageReference Include="Mono.Posix.NETStandard" Version="5.20.1-preview" />
     <PackageReference Include="coverlet.collector" Version="1.2.1" PrivateAssets="all" />
   </ItemGroup>
   <ItemGroup>

src/NzbDrone.Mono/Lidarr.Mono.csproj

@@ -14,7 +14,7 @@
        See https://github.com/xamarin/XamarinComponents/issues/282
   -->
   <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
-    <PackageReference Include="Mono.Posix.NETStandard" Version="1.0.0" />
+    <PackageReference Include="Mono.Posix.NETStandard" Version="5.20.1-preview" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\NzbDrone.Common\Lidarr.Common.csproj" />