diff --git a/src/main.rs b/src/main.rs
index 4b6aef2..c711554 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,10 +5,18 @@ use std::{
 use parking_lot::RwLock;
 use tar::Archive;
 
+#[derive(Clone)]
+struct OpenFile {
+    mount_id: usize,
+    file_offset: u64,
+    len: usize,
+    pos: u64,
+}
+
 #[derive(Clone)]
 struct Serv {
     mounts: Arc<RwLock<Vec<(File, Vec<(PathBuf, u64, usize)>)>>>,
-    files: Arc<RwLock<Vec<(usize, u64, usize)>>>,
+    files: Arc<RwLock<Vec<OpenFile>>>,
 }
 
 impl fs_rpc::Server for Serv {
@@ -40,48 +48,87 @@ impl fs_rpc::Server for Serv {
             .ok_or(())?;
         self.files
             .write()
-            .push((mount_id as usize, file_offset, file_size));
+            .push(OpenFile {
+                mount_id: mount_id as usize,
+                file_offset,
+                len: file_size,
+                pos: 0,
+            });
         Ok((None, (self.files.read().len() - 1) as u64))
     }
 
-    fn open_dir(&self, path: &std::path::Path, mount_id: u64) -> Result<(Option<u64>, u64), ()> {
+    fn open_dir(&self, _path: &std::path::Path, _mount_id: u64) -> Result<(Option<u64>, u64), ()> {
         // TODO
         Err(())
     }
 }
 
 impl file_rpc::Server for Serv {
-    fn read(&self, fd: u64, pos: u64, len: usize) -> Result<Cow<'_, [u8]>, ()> {
-        let (mount_id, file_offset, size) = self.files.read()[fd as usize];
-        let read_len = usize::min(len, size - (pos as usize));
+    fn read(&self, fd: u64, len: usize) -> Result<Cow<'_, [u8]>, ()> {
+        let files = self.files.read();
+        let file = &files[fd as usize];
+        let read_len = usize::min(len, file.len - (file.pos as usize));
         if read_len == 0 {
             return Ok(Vec::new().into());
         };
         let mounts = self.mounts.read();
-        let mount = &mounts[mount_id];
+        let mount = &mounts[file.mount_id];
         (&mount.0)
-            .seek(std::io::SeekFrom::Start(file_offset + pos))
+            .seek(std::io::SeekFrom::Start(file.file_offset + file.pos))
             .unwrap();
         let mut buf = vec![0; read_len];
         let read_bytes = (&mount.0).read(&mut buf).map_err(|_| ())?;
         buf.truncate(read_bytes);
+        std::mem::drop(files);
+        self.files.write()[fd as usize].pos += read_bytes as u64;
         Ok(buf.into())
     }
 
-    fn write(&self, _fd: u64, _pos: u64, _data: &[u8]) -> Result<(), ()> {
+    fn write(&self, _fd: u64, _data: &[u8]) -> Result<(), ()> {
         Err(())
     }
 
     fn close(&self, _fd: u64) {}
 
     fn size(&self, fd: u64) -> Option<u64> {
-        let (_mount_id, _file_offset, size) = self.files.read()[fd as usize];
-        Some(size as u64)
+        Some(self.files.read()[fd as usize].len as u64)
     }
 
     fn dup(&self, fd: u64) -> Option<u64> {
-        Some(fd)
+        let mut files = self.files.write();
+        let file = files[fd as usize].clone();
+        files.push(file);
+        Some((files.len() - 1) as u64)
     }
+
+    fn seek(&self, fd: u64, pos: file_rpc::SeekFrom) -> u64{
+        let mut files = self.files.write();
+        let file = &mut files[fd as usize];
+        match pos {
+            file_rpc::SeekFrom::Start(offset) => {
+                file.pos = offset;
+            },
+            file_rpc::SeekFrom::End(offset) => {
+                if offset <= 0 {
+                    file.pos = file.len as u64 - (-offset) as u64;
+                }
+            },
+            file_rpc::SeekFrom::Current(offset) => {
+                if offset > 0 {
+                    file.pos = u64::min(file.pos + offset as u64, file.len as u64);
+                } else {
+                    let offset = (-offset) as u64;
+                    if offset > file.pos {
+                        file.pos = 0;
+                    } else {
+                        file.pos -= offset;
+                    }
+                }
+            },
+        };
+        file.pos
+    }
+
 }
 
 fn main() {