diff --git a/Cargo.toml b/Cargo.toml
index b3ccdcf..d2a4af7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,3 +1,3 @@
 [workspace]
-members = ["judge-core", "judger"]
-resolver = "2"
\ No newline at end of file
+members = ["judge-core", "judger", "runguard"]
+resolver = "2"
diff --git a/runguard/Cargo.toml b/runguard/Cargo.toml
new file mode 100644
index 0000000..9a94cf5
--- /dev/null
+++ b/runguard/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "runguard"
+version = "0.1.0"
+edition = "2021"
+build = "build.rs"
+
+[dependencies]
+libc = "0.2"
+nix = { version = "0.29", features = ["signal"] }
+
+clap = { version = "4", features = ["derive"] }
+humantime = "2"
diff --git a/runguard/README.md b/runguard/README.md
new file mode 100644
index 0000000..03d6527
--- /dev/null
+++ b/runguard/README.md
@@ -0,0 +1,5 @@
+# runguard
+
+A Rust version of
+[Domjudge runguard](https://github.com/DOMjudge/domjudge/blob/main/judge/runguard.cc)
+written in C++.
diff --git a/runguard/build.rs b/runguard/build.rs
new file mode 100644
index 0000000..2368e89
--- /dev/null
+++ b/runguard/build.rs
@@ -0,0 +1,3 @@
+fn main() {
+    println!("cargo:rustc-link-lib=cgroup");
+}
\ No newline at end of file
diff --git a/runguard/src/cgroup.rs b/runguard/src/cgroup.rs
new file mode 100644
index 0000000..8046a1e
--- /dev/null
+++ b/runguard/src/cgroup.rs
@@ -0,0 +1,125 @@
+use std::ffi::CString;
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::os::raw::c_char;
+
+extern "C" {
+    fn cgroup_new_cgroup(name: *const c_char) -> *mut libc::c_void;
+    fn cgroup_strerror(err: i32) -> *const c_char;
+}
+
+pub enum CGroupError {
+    ECGROUPNOTCOMPILED = 50000,
+    ECGROUPNOTMOUNTED,
+    ECGROUPNOTEXIST,
+    ECGROUPNOTCREATED,
+    ECGROUPSUBSYSNOTMOUNTED,
+    ECGROUPNOTOWNER,
+    /** Controllers bound to different mount points */
+    ECGROUPMULTIMOUNTED,
+    /* This is the stock error. Default error. @todo really? */
+    ECGROUPNOTALLOWED,
+    ECGMAXVALUESEXCEEDED,
+    ECGCONTROLLEREXISTS,
+    ECGVALUEEXISTS,
+    ECGINVAL,
+    ECGCONTROLLERCREATEFAILED,
+    ECGFAIL,
+    ECGROUPNOTINITIALIZED,
+    ECGROUPVALUENOTEXIST,
+    /**
+     * Represents error coming from other libraries like glibc. @c libcgroup
+     * users need to check cgroup_get_last_errno() upon encountering this
+     * error.
+     */
+    ECGOTHER,
+    ECGROUPNOTEQUAL,
+    ECGCONTROLLERNOTEQUAL,
+    /** Failed to parse rules configuration file. */
+    ECGROUPPARSEFAIL,
+    /** Rules list does not exist. */
+    ECGROUPNORULES,
+    ECGMOUNTFAIL,
+    /**
+     * Not an real error, it just indicates that iterator has come to end
+     * of sequence and no more items are left.
+     */
+    ECGEOF = 50023,
+    /** Failed to parse config file (cgconfig.conf). */
+    ECGCONFIGPARSEFAIL,
+    ECGNAMESPACEPATHS,
+    ECGNAMESPACECONTROLLER,
+    ECGMOUNTNAMESPACE,
+    ECGROUPUNSUPP,
+    ECGCANTSETVALUE,
+    /** Removing of a group failed because it was not empty. */
+    ECGNONEMPTY,
+}
+
+struct CGroup {
+    cgroup: *mut libc::c_void,
+}
+
+impl CGroup {
+    fn new(name: &str) -> Self {
+        let cgroup_name = CString::new(name).expect("CString::new failed");
+        unsafe {
+            let cgroup = cgroup_new_cgroup(cgroup_name.as_ptr());
+            if cgroup.is_null() {
+                eprintln!("Failed to create new cgroup");
+            } else {
+                println!("Successfully created new cgroup {}", name);
+            }
+            CGroup { cgroup }
+        }
+    }
+}
+
+fn cgroup_is_v2() -> bool {
+    let file = match File::open("/proc/mounts") {
+        Ok(file) => file,
+        Err(_) => {
+            eprintln!("Error opening /proc/mounts");
+            return false;
+        }
+    };
+
+    let reader = io::BufReader::new(file);
+    for line in reader.lines() {
+        if let Ok(line) = line {
+            let parts: Vec<&str> = line.split_whitespace().collect();
+            if parts.len() >= 3 && parts[1] == "/sys/fs/cgroup" && parts[2] == "cgroup2" {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
+pub fn cgroup_strerror_safe(err: i32) -> String {
+    unsafe {
+        let errstr = cgroup_strerror(err);
+        let errstr = std::ffi::CStr::from_ptr(errstr).to_str().unwrap();
+        errstr.to_string()
+    }
+}
+
+#[test]
+fn test_cgroup() {
+    let _ = CGroup::new("my_cgroup");
+
+    if cgroup_is_v2() {
+        println!("cgroup v2 is enabled");
+    } else {
+        println!("cgroup v2 is not enabled");
+    }
+}
+
+#[test]
+fn test_cgroup_strerror() {
+    println!(
+        "{}",
+        cgroup_strerror_safe(CGroupError::ECGROUPNOTCOMPILED as i32)
+    );
+}
diff --git a/runguard/src/cli.rs b/runguard/src/cli.rs
new file mode 100644
index 0000000..8d51de4
--- /dev/null
+++ b/runguard/src/cli.rs
@@ -0,0 +1,102 @@
+use std::path;
+
+use clap::Parser;
+
+#[derive(Parser)]
+#[command(
+    override_usage = "runguard [OPTION]... <COMMAND>...",
+    about = "Run COMMAND with specified options.",
+    after_help = "Note that root privileges are needed for the `root' and `user' options. \
+If `user' is set, then `group' defaults to the same to prevent security issues, \
+since otherwise the process would retain group root permissions. \
+The COMMAND path is relative to the changed ROOT directory if specified. \
+TIME may be specified as a float; two floats separated by `:' are treated as soft and hard limits. \
+The runtime written to file is that of the last of wall/cpu time options set, \
+and defaults to CPU time when neither is set. \
+When run setuid without the `user' option, the user ID is set to the real user ID."
+)]
+pub struct Cli {
+    /// run COMMAND with root directory set to ROOT
+    #[arg(short, long)]
+    root: String,
+
+    /// run COMMAND as user with username or ID USER
+    #[arg(short, long)]
+    user: String,
+
+    /// run COMMAND under group with name or ID GROUP
+    #[arg(short, long)]
+    group: String,
+
+    /// change to directory DIR after setting root directory
+    #[arg(short = 'd', long, value_name = "DIR")]
+    chdir: String,
+
+    /// kill COMMAND after TIME wallclock seconds
+    #[arg(short = 't', long, value_name = "TIME")]
+    walltime: humantime::Duration,
+
+    /// set maximum CPU time to TIME seconds
+    #[arg(short = 'C', long, value_name = "TIME")]
+    cputime: humantime::Duration,
+
+    /// set total memory limit to SIZE kB
+    #[arg(short = 'm', long, value_name = "SIZE")]
+    memsize: u64,
+
+    /// set maximum created filesize to SIZE kB
+    #[arg(short = 'f', long, value_name = "SIZE")]
+    filesize: u64,
+
+    /// set maximum no. processes to N
+    #[arg(short = 'p', long, value_name = "N")]
+    nproc: u64,
+
+    /// use only processor number ID (or set, e.g. \"0,2-3\")
+    #[arg(short = 'P', long, value_name = "ID")]
+    cpuset: String,
+
+    /// disable core dumps
+    #[arg(short = 'c', long)]
+    no_core: bool,
+
+    /// redirect COMMAND stdout output to FILE
+    #[arg(short = 'o', long, value_name = "FILE")]
+    stdout: path::PathBuf,
+
+    /// redirect COMMAND stderr output to FILE
+    #[arg(short = 'e', long, value_name = "FILE")]
+    stderr: path::PathBuf,
+
+    /// truncate COMMAND stdout/stderr streams at SIZE kB
+    #[arg(short, long, value_name = "SIZE")]
+    streamsize: u64,
+
+    /// preserve environment variables (default only PATH)
+    #[arg(short = 'E', long)]
+    environment: String,
+
+    /// write metadata (runtime, exitcode, etc.) to FILE
+    #[arg(short = 'M', long, value_name = "FILE")]
+    metadata: path::PathBuf,
+
+    /// process ID of runpipe to send SIGUSR1 signal when
+    /// timelimit is reached
+    #[arg(short = 'U', long, value_name = "PID")]
+    runpipepid: u32,
+
+    /// display some extra warnings and information
+    #[arg(short, long)]
+    verbose: bool,
+
+    /// suppress all warnings and verbose output
+    #[arg(short, long)]
+    quiet: bool,
+
+    /// output version information and exit
+    #[arg(long)]
+    version: bool,
+
+    #[arg(required = true)]
+    command: Vec<String>,
+}
diff --git a/runguard/src/context.rs b/runguard/src/context.rs
new file mode 100644
index 0000000..27a8d0e
--- /dev/null
+++ b/runguard/src/context.rs
@@ -0,0 +1,105 @@
+use std::{fmt::Arguments, fs::File, io::Write};
+
+use nix::sys::signal::{
+    sigprocmask, SigSet,
+    SigmaskHow::SIG_BLOCK,
+    Signal::{SIGALRM, SIGTERM},
+};
+
+use crate::{
+    cgroup::{cgroup_strerror_safe, CGroupError},
+    safe_libc::{fclose, strerror},
+    PROGNAME,
+};
+
+struct Context {
+    outputmeta: bool,
+    metafile: Option<File>,
+    metafilename: String,
+
+    errno: i32,
+    in_error_handling: bool,
+}
+
+impl Context {
+    fn error(&mut self, errnum: i32, format: Arguments) {
+        // Silently ignore errors that happen while handling other errors.
+        if self.in_error_handling {
+            return;
+        }
+        self.in_error_handling = true;
+
+        /*
+         * Make sure the signal handler for these (terminate()) does not
+         * interfere, we are exiting now anyway.
+         */
+        let mut sigs: SigSet = SigSet::empty();
+        sigs.add(SIGALRM);
+        sigs.add(SIGTERM);
+        let _ = sigprocmask(SIG_BLOCK, Some(&sigs), None);
+
+        /* First print to string to be able to reuse the message. */
+        let mut errstr: String = PROGNAME.to_string();
+        if !format.to_string().is_empty() {
+            errstr = format!("{}: {}", errstr, strerror(errnum));
+        }
+        if errnum != 0 {
+            /* Special case libcgroup error codes. */
+            if errnum == CGroupError::ECGOTHER as i32 {
+                errstr = format!("{}: libcgroup", errstr);
+            }
+            if errnum == CGroupError::ECGROUPNOTCOMPILED as i32 {
+                errstr = format!("{}: {}", errstr, cgroup_strerror_safe(errnum));
+            } else {
+                errstr = format!("{}: {}", errstr, strerror(errnum));
+            }
+        }
+        if format.to_string().is_empty() && errnum == 0 {
+            errstr = format!("{}: unknown error", errstr);
+        }
+
+        self.write_meta("internal-error", format_args!("{}", errstr));
+        if self.outputmeta && self.metafile.is_some() {
+            if let Some(file_ref) = &self.metafile {
+                if fclose(file_ref.try_clone().unwrap()) != 0 {
+                    eprintln!("\nError closing metafile '{}'.\n", self.metafilename);
+                }
+            }
+        }
+
+        eprintln!(
+            "{}\nTry `{} --help' for more information.",
+            errstr, PROGNAME
+        );
+    }
+
+    fn write_meta(&mut self, key: &str, format: Arguments) {
+        if !self.outputmeta {
+            return;
+        }
+
+        if let Some(file) = self.metafile.as_mut() {
+            if writeln!(file, "{}: {}", key, format).is_err() {
+                self.outputmeta = false;
+                self.error(0, format_args!("cannot write to file: {}", "metafile.txt"));
+            }
+        } else {
+            self.outputmeta = false;
+            self.error(0, format_args!("cannot write to file: {}", "metafile.txt"));
+        }
+    }
+}
+
+#[test]
+fn test_context() {
+    let mut ctx = Context {
+        outputmeta: true,
+        metafile: Some(File::create("metafile.txt").unwrap()),
+        metafilename: "metafile.txt".to_string(),
+        errno: 0,
+        in_error_handling: false,
+    };
+
+    ctx.error(0, format_args!("test error"));
+    ctx.write_meta("test", format_args!("test meta"));
+}
\ No newline at end of file
diff --git a/runguard/src/main.rs b/runguard/src/main.rs
new file mode 100644
index 0000000..0768637
--- /dev/null
+++ b/runguard/src/main.rs
@@ -0,0 +1,12 @@
+use clap::Parser;
+
+mod cgroup;
+mod cli;
+mod context;
+mod safe_libc;
+
+const PROGNAME: &str = "runguard";
+
+fn main() {
+    let _ = cli::Cli::parse();
+}
diff --git a/runguard/src/safe_libc.rs b/runguard/src/safe_libc.rs
new file mode 100644
index 0000000..61493a3
--- /dev/null
+++ b/runguard/src/safe_libc.rs
@@ -0,0 +1,25 @@
+use std::{fs::File, os::fd::IntoRawFd};
+
+pub fn strerror(errnum: i32) -> String {
+    unsafe {
+        let errstr = libc::strerror(errnum);
+        let errstr = std::ffi::CStr::from_ptr(errstr).to_str().unwrap();
+        errstr.to_string()
+    }
+}
+
+pub fn fclose(file: File) -> i32 {
+    let fd = file.into_raw_fd();
+    unsafe { libc::close(fd) }
+}
+
+#[test]
+fn test_strerror() {
+    println!("{}", strerror(libc::EINVAL));
+}
+
+#[test]
+fn test_fclose() {
+    let file = File::open("/dev/null").unwrap();
+    assert_eq!(fclose(file), 0);
+}
\ No newline at end of file