diff --git a/src/libos/src/entry.rs b/src/libos/src/entry.rs
index e8b46a80..5e57d86d 100644
--- a/src/libos/src/entry.rs
+++ b/src/libos/src/entry.rs
@@ -5,6 +5,7 @@ use util::mem_util::from_untrusted::*;
 
 #[no_mangle]
 pub extern "C" fn libos_boot(path_buf: *const c_char, argv: *const *const c_char) -> i32 {
+    util::log::init();
     let (path, args) = match parse_arguments(path_buf, argv) {
         Ok(path_and_args) => path_and_args,
         Err(_) => {
diff --git a/src/libos/src/syscall/mod.rs b/src/libos/src/syscall/mod.rs
index bf60348f..507c3d12 100644
--- a/src/libos/src/syscall/mod.rs
+++ b/src/libos/src/syscall/mod.rs
@@ -27,6 +27,7 @@ pub extern "C" fn dispatch_syscall(
     arg4: isize,
     arg5: isize,
 ) -> isize {
+    debug!("syscall {}: {:#x}, {:#x}, {:#x}, {:#x}, {:#x}, {:#x}", num, arg0, arg1, arg2, arg3, arg4, arg5);
     let ret = match num {
         SYS_open => do_open(arg0 as *const i8, arg1 as u32, arg2 as u32),
         SYS_close => do_close(arg0 as FileDesc),
diff --git a/src/libos/src/util/log.rs b/src/libos/src/util/log.rs
new file mode 100644
index 00000000..0c786d1c
--- /dev/null
+++ b/src/libos/src/util/log.rs
@@ -0,0 +1,88 @@
+use log::*;
+
+pub fn init() {
+    static LOGGER: SimpleLogger = SimpleLogger;
+    log::set_logger(&LOGGER).unwrap();
+    log::set_max_level(match option_env!("LOG") {
+        Some("error") => LevelFilter::Error,
+        Some("warn") => LevelFilter::Warn,
+        Some("info") => LevelFilter::Info,
+        Some("debug") => LevelFilter::Debug,
+        Some("trace") => LevelFilter::Trace,
+        _ => LevelFilter::Off,
+    });
+}
+
+struct SimpleLogger;
+
+impl Log for SimpleLogger {
+    fn enabled(&self, _metadata: &Metadata) -> bool {
+        true
+    }
+    fn log(&self, record: &Record) {
+        if self.enabled(record.metadata()) {
+            let color = Color::from(record.level());
+            let (show, code) = color.to_console_code();
+            println!("\u{1B}[{};{}m[{:>5}] {}\u{1B}[0m",
+                     show, code + 30, record.level(), record.args());
+        }
+    }
+    fn flush(&self) {}
+}
+
+impl From<Level> for Color {
+    fn from(level: Level) -> Self {
+        match level {
+            Level::Error => Color::Red,
+            Level::Warn => Color::Yellow,
+            Level::Info => Color::Blue,
+            Level::Debug => Color::Green,
+            Level::Trace => Color::DarkGray,
+        }
+    }
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+#[repr(u8)]
+pub enum Color {
+    Black = 0,
+    Blue = 1,
+    Green = 2,
+    Cyan = 3,
+    Red = 4,
+    Magenta = 5,
+    Brown = 6,
+    LightGray = 7,
+    DarkGray = 8,
+    LightBlue = 9,
+    LightGreen = 10,
+    LightCyan = 11,
+    LightRed = 12,
+    Pink = 13,
+    Yellow = 14,
+    White = 15,
+}
+
+impl Color {
+    fn to_console_code(&self) -> (u8, u8) {
+        match self {
+            Color::Black => (0, 0),
+            Color::Blue => (0, 4),
+            Color::Green => (0, 2),
+            Color::Cyan => (0, 6),
+            Color::Red => (0, 1),
+            Color::Magenta => (0, 5),
+            Color::Brown => (0, 3),
+            Color::LightGray => (1, 7),
+            Color::DarkGray => (0, 7),
+            Color::LightBlue => (1, 4),
+            Color::LightGreen => (1, 2),
+            Color::LightCyan => (1, 6),
+            Color::LightRed => (1, 1),
+            Color::Pink => (1, 5),
+            Color::Yellow => (1, 3),
+            Color::White => (1, 0),
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/libos/src/util/mod.rs b/src/libos/src/util/mod.rs
index b408539c..20c084fb 100644
--- a/src/libos/src/util/mod.rs
+++ b/src/libos/src/util/mod.rs
@@ -3,3 +3,4 @@ use super::*;
 pub mod mem_util;
 pub mod mpx_util;
 pub mod ring_buf;
+pub mod log;