Drop root privileges on startup

On rooted devices, switch to user 2000 during startup.

Copy-paste does not work as root (user 0), so switching to 2000 fixes
the issue.

Fixes #6224 <https://github.com/Genymobile/scrcpy/issues/6224>

Suggested-by: Simon Chan <1330321+yume-chan@users.noreply.github.com>

LICENSE

@@ -188,7 +188,7 @@
       identification within third-party archives.
 
    Copyright (C) 2018 Genymobile
-   Copyright (C) 2018-2026 Romain Vimont
+   Copyright (C) 2018-2025 Romain Vimont
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

README.md

@@ -210,7 +210,7 @@ work][donate]:
 ## License
 
     Copyright (C) 2018 Genymobile
-    Copyright (C) 2018-2026 Romain Vimont
+    Copyright (C) 2018-2025 Romain Vimont
 
     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.

app/scrcpy.1

@@ -852,7 +852,7 @@ Report bugs to <https://github.com/Genymobile/scrcpy/issues>.
 .SH COPYRIGHT
 Copyright \(co 2018 Genymobile <https://www.genymobile.com>
 
-Copyright \(co 2018\-2026 Romain Vimont <rom@rom1v.com>
+Copyright \(co 2018\-2025 Romain Vimont <rom@rom1v.com>
 
 Licensed under the Apache License, Version 2.0.
 

doc/build.md

@@ -172,7 +172,8 @@ Additionally, if you want to build the server, install Java 17 from Caskroom, an
 make it available from the `PATH`:
 
 ```bash
-brew install openjdk@17
+brew tap homebrew/cask-versions
+brew install adoptopenjdk/openjdk/adoptopenjdk17
 export JAVA_HOME="$(/usr/libexec/java_home --version 1.17)"
 export PATH="$JAVA_HOME/bin:$PATH"
 ```

server/src/main/java/com/genymobile/scrcpy/Server.java

@@ -27,6 +27,8 @@ import com.genymobile.scrcpy.video.VideoSource;
 import android.annotation.SuppressLint;
 import android.os.Build;
 import android.os.Looper;
+import android.system.ErrnoException;
+import android.system.Os;
 
 import java.io.File;
 import java.io.IOException;
@@ -233,6 +235,8 @@ public final class Server {
             }
         });
 
+        dropRootPrivileges();
+
         prepareMainLooper();
 
         Options options = Options.parse(args);
@@ -273,4 +277,17 @@ public final class Server {
             // Do not print stack trace, a user-friendly error-message has already been logged
         }
     }
+
+    @SuppressWarnings("deprecation")
+    private static void dropRootPrivileges() {
+        try {
+            if (Os.getuid() == 0) {
+                // Copy-paste does not work with root user
+                // <https://github.com/Genymobile/scrcpy/issues/6224>
+                Os.setuid(2000);
+            }
+        } catch (Exception e) {
+            Ln.w("Cannot set UID", e);
+        }
+    }
 }