move IsRoot to posix identity

move checking root to CheckSystemCompatibility
use Syscall internal getuid

src/Tgstation.Server.Host/Components/InstanceManager.cs

@@ -675,6 +675,11 @@ namespace Tgstation.Server.Host.Components
 			{
 				if (!systemIdentity.CanCreateSymlinks)
 					throw new InvalidOperationException($"The user running {Constants.CanonicalPackageName} cannot create symlinks! Please try running as an administrative user!");
+
+				if (systemIdentity is PosixSystemIdentity posixIdentity && posixIdentity.IsRoot())
+				{
+					logger.LogWarning("TGS is being run as the root account. This is not recommended and may prevent launch in a future version.");
+				}
 			}
 
 			// This runs before the real socket is opened, ensures we don't perform reattaches unless we're fairly certain the bind won't fail

src/Tgstation.Server.Host/Program.cs

@@ -11,7 +11,6 @@ using Tgstation.Server.Host.Core;
 using Tgstation.Server.Host.Properties;
 using Tgstation.Server.Host.System;
 
-using InteropServices = System.Runtime.InteropServices;
 using Process = System.Diagnostics.Process;
 
 namespace Tgstation.Server.Host
@@ -70,34 +69,6 @@ namespace Tgstation.Server.Host
 				args = listArgs.ToArray();
 			}
 
-			if (InteropServices.RuntimeInformation.IsOSPlatform(InteropServices.OSPlatform.Linux))
-			{
-				using var proc = new Process
-				{
-					StartInfo = new ProcessStartInfo
-					{
-						FileName = "id",
-						Arguments = "-u",
-						UseShellExecute = false,
-						RedirectStandardOutput = true,
-						CreateNoWindow = true,
-					},
-				};
-
-				proc.Start();
-				await proc.WaitForExitAsync();
-				if (proc.ExitCode is not 0 || !int.TryParse(await proc.StandardOutput.ReadToEndAsync(), out var uid))
-				{
-					Console.Error.WriteLine("Failed to obtain user id.");
-					return 1;
-				}
-
-				if (uid is 0)
-				{
-					Console.Error.WriteLine("TGS is being run as root. This is not recommended and will prevent launching in a future version!");
-				}
-			}
-
 			var program = new Program();
 			return (int)await program.Main(args, updatePath);
 		}

src/Tgstation.Server.Host/Security/PosixSystemIdentity.cs

@@ -2,6 +2,8 @@
 using System.Threading;
 using System.Threading.Tasks;
 
+using Mono.Unix.Native;
+
 namespace Tgstation.Server.Host.Security
 {
 	/// <summary>
@@ -9,6 +11,32 @@ namespace Tgstation.Server.Host.Security
 	/// </summary>
 	sealed class PosixSystemIdentity : ISystemIdentity
 	{
+		/// <summary>
+		/// True if TGS is running under root.
+		/// </summary>
+		bool isRoot = false;
+
+		/// <summary>
+		/// True if <see cref="isRoot" /> is populated.
+		/// </summary>
+		bool isRootChecked = false;
+
+		/// <summary>
+		/// Checks whether TGS is running under the root user.
+		/// </summary>
+		/// <returns>True if running under root. False otherwise.</returns>
+		public bool IsRoot()
+		{
+			if (isRootChecked)
+			{
+				return isRoot;
+			}
+
+			isRoot = Syscall.getuid() == 0;
+			isRootChecked = true;
+			return isRoot;
+		}
+
 		/// <inheritdoc />
 		public string Uid => throw new NotImplementedException();