diff --git a/Cargo.lock b/Cargo.lock
index dced6a0507..da530d426e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,5 +1,22 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+[[package]]
+name = "bitflags"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
+
 [[package]]
 name = "ramfs"
 version = "0.1.0"
+dependencies = [
+ "redox_syscall",
+]
+
+[[package]]
+name = "redox_syscall"
+version = "0.1.56"
+source = "git+https://gitlab.redox-os.org/redox-os/syscall.git#8d0015be8693a81c2a4459f3c09fb47b98ff07b1"
+dependencies = [
+ "bitflags",
+]
diff --git a/Cargo.toml b/Cargo.toml
index 67e63c6704..af4002d300 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,3 +7,4 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+redox_syscall = { git = "https://gitlab.redox-os.org/redox-os/syscall.git" }
diff --git a/src/filesystem.rs b/src/filesystem.rs
new file mode 100644
index 0000000000..90dde31672
--- /dev/null
+++ b/src/filesystem.rs
@@ -0,0 +1,68 @@
+use std::collections::BTreeMap;
+use std::os::unix::io::AsRawFd;
+use std::fs;
+
+use syscall::{Error, Result, StatVfs, TimeSpec};
+use syscall::error::EIO;
+use syscall::flag::{O_RDONLY, O_STAT};
+
+pub struct File {
+    pub mode: u16,
+    pub uid: u32,
+    pub gid: u32,
+    pub ino: usize,
+    pub nlink: usize,
+
+    pub atime: TimeSpec,
+    pub ctime: TimeSpec,
+    pub mtime: TimeSpec,
+    pub crtime: TimeSpec,
+
+    pub data: FileData,
+}
+
+pub enum FileData {
+    File(Vec<u8>),
+    Directory(Vec<Vec<u8>>),
+}
+impl FileData {
+    pub fn size(&self) -> usize {
+        match self {
+            &Self::File(ref data) => data.len(),
+            &Self::Directory(ref names) => names.iter().map(|name| name.len()).sum(),
+        }
+    }
+}
+
+pub struct Filesystem {
+    pub files: BTreeMap<usize, File>,
+    pub tree: BTreeMap<Vec<u8>, usize>,
+    pub memory_file: fs::File,
+}
+impl Filesystem {
+    pub const DEFAULT_BLOCK_SIZE: u32 = 4096;
+
+    pub fn new() -> Result<Self> {
+        Ok(Self {
+            files: BTreeMap::new(),
+            tree: BTreeMap::new(),
+            memory_file: fs::File::open("memory:").or(Err(Error::new(EIO)))?,
+        })
+    }
+    pub fn get_block_size(&self) -> Result<u32> {
+        let mut statvfs = StatVfs::default();
+        syscall::fstatvfs(self.memory_file.as_raw_fd() as usize, &mut statvfs)?;
+        Ok(statvfs.f_bsize)
+    }
+    pub fn block_size(&self) -> u32 {
+        self.get_block_size().unwrap_or(Self::DEFAULT_BLOCK_SIZE)
+    }
+    pub fn resolve(&self, mut path: &[u8], uid: u32, gid: u32) -> Option<usize> {
+        // TODO: CoW
+        let mut path = path.to_owned();
+        // TODO: Replace follow symlinks, and replace double slashes with single slashes.
+
+        // TODO: Check that every directory in the path grant the user the search permission.
+        self.tree.get(&path).copied()
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index e7a11a969c..8879cd7985 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,39 @@
+#![feature(try_reserve)]
+
+use std::fs::File;
+use std::io::prelude::*;
+use std::env;
+
+use syscall::{CloneFlags, Packet, SchemeMut};
+
+mod filesystem;
+mod scheme;
+
+use self::scheme::Scheme;
+
 fn main() {
-    println!("Hello, world!");
+    let scheme_name = env::args().nth(1).expect("Usage:\n\tramfs SCHEME_NAME");
+    let mut socket = File::create(format!(":{}", scheme_name)).expect("ramfs: failed to create socket");
+
+    if unsafe { syscall::clone(CloneFlags::empty()) }.expect("ramfs: failed to fork") != 0 {
+        return;
+    }
+
+    let mut scheme = Scheme::new(scheme_name).expect("ramfs: failed to initialize scheme");
+
+    loop {
+        let mut packet = Packet::default();
+        match socket.read(&mut packet) {
+            Ok(0) => break,
+            Ok(_) => (),
+            Err(error) => panic!("ramfs: failed to read from socket: {:?}", error),
+        }
+        scheme.handle(&mut packet);
+
+        match socket.write(&packet) {
+            Ok(0) => break,
+            Ok(_) => (),
+            Err(error) => panic!("ramfs: failed to write to socket: {:?}", error),
+        }
+    }
 }
diff --git a/src/scheme.rs b/src/scheme.rs
new file mode 100644
index 0000000000..f458750294
--- /dev/null
+++ b/src/scheme.rs
@@ -0,0 +1,319 @@
+use std::collections::BTreeMap;
+use std::convert::{TryFrom, TryInto};
+use std::os::unix::io::AsRawFd;
+use std::{cmp, ops};
+
+use syscall::{Error, EventFlags, Map, Result, SchemeMut, Stat, StatVfs, TimeSpec};
+use syscall::flag::{O_RDWR, O_RDONLY, O_WRONLY, O_DIRECTORY, O_STAT};
+use syscall::{MODE_DIR, MODE_PERM, MODE_TYPE, SEEK_CUR, SEEK_END, SEEK_SET};
+use syscall::error::{EACCES, EBADF, EBADFD, EFBIG, EINVAL, EISDIR, ENOENT, ENOMEM, ENOSYS, ENOTDIR, EOPNOTSUPP, EOVERFLOW};
+
+use crate::filesystem::{FileData, Filesystem};
+
+#[derive(Clone)]
+struct Handle {
+    inode: usize,
+    offset: usize,
+}
+
+pub struct Scheme {
+    scheme_name: String,
+    handles: BTreeMap<usize, Handle>,
+    next_fd: usize,
+    filesystem: Filesystem,
+}
+impl Scheme {
+    pub fn new(scheme_name: String) -> Result<Self> {
+        Ok(Self {
+            scheme_name,
+            handles: BTreeMap::new(),
+            filesystem: Filesystem::new()?,
+            next_fd: 0,
+        })
+    }
+}
+
+impl SchemeMut for Scheme {
+    fn open(&mut self, path: &[u8], flags: usize, uid: u32, gid: u32) -> Result<usize> {
+        let inode = self.filesystem.resolve(path, uid, gid).ok_or(Error::new(ENOENT))?;
+        let file = self.filesystem.files.get(&inode).ok_or(Error::new(ENOENT))?;
+
+        if flags & O_STAT == 0 && flags & O_DIRECTORY != 0 && file.mode & MODE_TYPE != MODE_DIR {
+            return Err(Error::new(ENOTDIR));
+        }
+        if flags & O_STAT == 0 && flags & O_DIRECTORY == 0 && file.mode & MODE_TYPE == MODE_DIR {
+            return Err(Error::new(EISDIR));
+        }
+
+        let perm = file.mode & MODE_PERM;
+        
+        if uid == file.uid {
+            check_permissions(flags, (perm & 0o700) >> 6)?;
+        } else if gid == file.gid {
+            check_permissions(flags, (perm & 0o70) >> 3)?;
+        } else {
+            check_permissions(flags, perm & 0o7)?;
+        }
+
+        let handle = Handle {
+            inode,
+            offset: 0,
+        };
+
+        let fd = self.next_fd;
+        self.next_fd += 1;
+
+        self.handles.insert(fd, handle);
+
+        Ok(fd)
+    }
+    fn chmod(&mut self, path: &[u8], mode: u16, uid: u32, gid: u32) -> Result<usize> {
+        // TODO
+        Err(Error::new(ENOSYS))
+    }
+    fn rmdir(&mut self, path: &[u8], uid: u32, gid: u32) -> Result<usize> {
+        // TODO
+        Err(Error::new(ENOSYS))
+    }
+    fn unlink(&mut self, path: &[u8], uid: u32, gid: u32) -> Result<usize> {
+        // TODO
+        Err(Error::new(ENOSYS))
+    }
+    fn dup(&mut self, old_fd: usize, _buf: &[u8]) -> Result<usize> {
+        let handle = self.handles.get_mut(&old_fd).ok_or(Error::new(EBADF))?.clone();
+
+        let fd = self.next_fd;
+        self.next_fd += 1;
+
+        self.handles.insert(fd, handle);
+        Ok(fd)
+    }
+    fn read(&mut self, fd: usize, buf: &mut [u8]) -> Result<usize> {
+        let handle = self.handles.get_mut(&fd).ok_or(Error::new(EBADF))?;
+        let file = self.filesystem.files.get_mut(&handle.inode).ok_or(Error::new(EBADFD))?;
+
+        match file.data {
+            FileData::File(ref bytes) => {
+                if file.mode & MODE_TYPE == MODE_DIR { return Err(Error::new(EBADFD)) }
+                if handle.offset >= bytes.len() {
+                    return Ok(0);
+                }
+                let bytes_to_read = cmp::min(bytes.len(), buf.len() + handle.offset) - handle.offset;
+                buf[..bytes_to_read].copy_from_slice(&bytes[handle.offset..handle.offset + bytes_to_read]);
+                Ok(bytes_to_read)
+            }
+            FileData::Directory(ref entries) => {
+                if file.mode & MODE_TYPE != MODE_DIR { return Err(Error::new(EBADFD)) }
+
+                let mut bytes_to_skip = handle.offset;
+                let mut bytes_left_to_read = buf.len();
+                let mut bytes_read = 0;
+
+                for entry_bytes in entries {
+                    // skip the whole entry if it fits
+                    if bytes_to_skip >= entry_bytes.len() {
+                        bytes_to_skip -= entry_bytes.len();
+                        continue;
+                    }
+
+                    let bytes_to_read = cmp::min(entry_bytes.len() - bytes_to_skip, bytes_left_to_read);
+
+                    let entry_bytes = &entry_bytes[bytes_to_skip..bytes_to_skip + bytes_to_read];
+                    bytes_to_skip -= bytes_to_skip;
+
+                    buf[handle.offset..handle.offset + bytes_to_read].copy_from_slice(&entry_bytes[..bytes_to_read]);
+                    bytes_left_to_read -= bytes_to_read;
+                    bytes_read += bytes_to_read;
+                }
+                Ok(bytes_read)
+            }
+        }
+    }
+    fn write(&mut self, fd: usize, buf: &[u8]) -> Result<usize> {
+        let handle = self.handles.get_mut(&fd).ok_or(Error::new(EBADF))?;
+        let file = self.filesystem.files.get_mut(&handle.inode).ok_or(Error::new(EBADFD))?;
+
+        if let &mut FileData::File(ref mut bytes) = &mut file.data {
+            if file.mode & MODE_TYPE == MODE_DIR { return Err(Error::new(EBADFD)) }
+
+            // if there's a seek hole, fill it with 0 and continue writing.
+            if handle.offset > bytes.len() {
+                let additional = handle.offset - bytes.len();
+                bytes.try_reserve(additional).or(Err(Error::new(ENOMEM)))?;
+                bytes.resize(handle.offset, 0u8);
+            }
+            bytes.extend(buf);
+            Ok(buf.len())
+        } else {
+            Err(Error::new(EISDIR))
+        }
+    }
+    fn seek(&mut self, fd: usize, pos: usize, whence: usize) -> Result<usize> {
+        let handle = self.handles.get_mut(&fd).ok_or(Error::new(EBADF))?;
+        let file = self.filesystem.files.get_mut(&handle.inode).ok_or(Error::new(EBADFD))?;
+
+        // cast to isize, possibly making the offset negative
+        let pos = pos as isize;
+
+        handle.offset = match whence {
+            SEEK_SET => cmp::max(0, pos) as usize,
+            SEEK_CUR => cmp::max(0, pos + isize::try_from(handle.offset).or(Err(Error::new(EOVERFLOW)))?) as usize,
+            SEEK_END => cmp::max(0, pos + isize::try_from(file.data.size()).or(Err(Error::new(EOVERFLOW)))?) as usize,
+            _ => return Err(Error::new(EINVAL)),
+        };
+        Ok(handle.offset)
+    }
+    fn fchmod(&mut self, fd: usize, mode: u16) -> Result<usize> {
+        let handle = self.handles.get_mut(&fd).ok_or(Error::new(EBADF))?;
+        let file = self.filesystem.files.get_mut(&handle.inode).ok_or(Error::new(EBADFD))?;
+
+        // TODO: Check that no file becomes a directory etc.
+        file.mode = mode;
+
+        Ok(0)
+    }
+    fn fchown(&mut self, fd: usize, uid: u32, gid: u32) -> Result<usize> {
+        let handle = self.handles.get_mut(&fd).ok_or(Error::new(EBADF))?;
+        let file = self.filesystem.files.get_mut(&handle.inode).ok_or(Error::new(EBADFD))?;
+
+        file.uid = uid;
+        file.gid = gid;
+
+        Ok(0)
+    }
+    fn fcntl(&mut self, fd: usize, _cmd: usize, _arg: usize) -> Result<usize> {
+        if ! self.handles.contains_key(&fd) {
+            return Err(Error::new(EBADF));
+        }
+        Ok(0)
+    }
+    fn fevent(&mut self, fd: usize, _flags: EventFlags) -> Result<EventFlags> {
+        if ! self.handles.contains_key(&fd) {
+            return Err(Error::new(EBADF));
+        }
+        Err(Error::new(ENOSYS))
+    }
+    fn fmap(&mut self, fd: usize, _map: &Map) -> Result<usize> {
+        if ! self.handles.contains_key(&fd) {
+            return Err(Error::new(EBADF));
+        }
+        // TODO
+        Err(Error::new(ENOSYS))
+    }
+    fn funmap(&mut self, _address: usize) -> Result<usize> {
+        // TODO
+        Err(Error::new(ENOSYS))
+    }
+    fn fpath(&mut self, fd: usize, buf: &mut [u8]) -> Result<usize> {
+        if ! self.handles.contains_key(&fd) {
+            return Err(Error::new(EBADF));
+        }
+        // TODO
+        Err(Error::new(ENOSYS))
+    }
+    fn frename(&mut self, fd: usize, path: &[u8], uid: u32, gid: u32) -> Result<usize> {
+        if ! self.handles.contains_key(&fd) {
+            return Err(Error::new(EBADF));
+        }
+        // TODO
+        Err(Error::new(ENOSYS))
+    }
+    fn fstat(&mut self, fd: usize, stat: &mut Stat) -> Result<usize> {
+        let handle = self.handles.get_mut(&fd).ok_or(Error::new(EBADF))?;
+        let block_size = self.filesystem.block_size();
+        let file = self.filesystem.files.get_mut(&handle.inode).ok_or(Error::new(EBADFD))?;
+
+        *stat = Stat {
+            st_mode: file.mode,
+            st_uid: file.uid,
+            st_gid: file.gid,
+            st_ino: handle.inode.try_into().or(Err(Error::new(EOVERFLOW)))?,
+            st_nlink: file.nlink.try_into().or(Err(Error::new(EOVERFLOW)))?,
+            st_dev: 0,
+
+            st_size: file.data.size().try_into().or(Err(Error::new(EOVERFLOW)))?,
+            st_blksize: block_size,
+            st_blocks: div_round_up(stat.st_size, u64::from(stat.st_blksize)),
+
+            st_atime: file.atime.tv_sec.try_into().or(Err(Error::new(EOVERFLOW)))?,
+            st_atime_nsec: file.atime.tv_nsec.try_into().or(Err(Error::new(EOVERFLOW)))?,
+
+            st_ctime: file.ctime.tv_sec.try_into().or(Err(Error::new(EOVERFLOW)))?,
+            st_ctime_nsec: file.ctime.tv_nsec.try_into().or(Err(Error::new(EOVERFLOW)))?,
+
+            st_mtime: file.mtime.tv_sec.try_into().or(Err(Error::new(EOVERFLOW)))?,
+            st_mtime_nsec: file.mtime.tv_nsec.try_into().or(Err(Error::new(EOVERFLOW)))?,
+        };
+
+        Ok(0)
+    }
+    fn fstatvfs(&mut self, fd: usize, stat: &mut StatVfs) -> Result<usize> {
+        if ! self.handles.contains_key(&fd) {
+            return Err(Error::new(EBADF));
+        }
+        syscall::fstatvfs(self.filesystem.memory_file.as_raw_fd() as usize, stat)?;
+
+        Ok(0)
+    }
+    fn fsync(&mut self, fd: usize) -> Result<usize> {
+        if ! self.handles.contains_key(&fd) {
+            return Err(Error::new(EBADF));
+        }
+        Ok(0)
+    }
+    fn ftruncate(&mut self, fd: usize, size: usize) -> Result<usize> {
+        let handle = self.handles.get_mut(&fd).ok_or(Error::new(EBADF))?;
+        let file = self.filesystem.files.get_mut(&handle.inode).ok_or(Error::new(EBADFD))?;
+
+        if file.mode & MODE_TYPE == MODE_DIR {
+            return Err(Error::new(EISDIR));
+        }
+        match &mut file.data {
+            &mut FileData::File(ref mut bytes) => {
+                if size > bytes.len() {
+                    let additional = size - bytes.len();
+                    bytes.try_reserve(additional).or(Err(Error::new(ENOMEM)))?;
+                    bytes.resize(size, 0u8)
+                } else {
+                    bytes.resize(size, 0u8)
+                }
+            }
+            &mut FileData::Directory(_) => return Err(Error::new(EBADFD)),
+        }
+        Ok(0)
+    }
+    fn futimens(&mut self, fd: usize, times: &[TimeSpec]) -> Result<usize> {
+        let handle = self.handles.get_mut(&fd).ok_or(Error::new(EBADF))?;
+        let file = self.filesystem.files.get_mut(&handle.inode).ok_or(Error::new(EBADFD))?;
+
+        let new_atime = *times.get(0).ok_or(Error::new(EINVAL))?;
+        let new_mtime = *times.get(1).ok_or(Error::new(EINVAL))?;
+
+        file.atime = new_atime;
+        file.mtime = new_mtime;
+
+        Ok(0)
+    }
+    fn close(&mut self, fd: usize) -> Result<usize> {
+        if self.handles.remove(&fd).is_none() {
+            return Err(Error::new(EBADF));
+        }
+        Ok(0)
+    }
+}
+fn div_round_up<T>(numer: T, denom: T) -> T
+where
+    T: Copy + ops::Add<T, Output = T> + ops::Sub<T, Output = T> + ops::Div<T, Output = T> + From<u8>,
+{
+    (numer + (denom - T::from(1u8))) / denom
+}
+fn check_permissions(flags: usize, single_mode: u16) -> Result<()> {
+    if flags & O_RDWR == O_RDONLY && single_mode & 0o4 == 0 {
+        return Err(Error::new(EACCES));
+    } else if flags & O_RDWR == O_WRONLY && single_mode & 0o2 == 0 {
+        return Err(Error::new(EACCES));
+    } else if flags & O_RDWR == O_RDWR && single_mode & 0o6 != 0o6 {
+        return Err(Error::new(EACCES));
+    }
+    Ok(())
+}