diff --git a/README.md b/README.md
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+# Sandbox RootFS NG
+This is the sandbox's rootfs used by [syzoj-ng-judge](https://github.com/syzoj/syzoj-ng-judge). It's based on Ubuntu 20.04 and contains compilers (and interpreters) below:
+
+* GCC 10
+* Clang 11 (from [LLVM](https://apt.llvm.org/))
+* OpenJDK 11
+* Kotlin (from [SDKMAN!](https://kotlinlang.org/docs/tutorials/command-line.html))
+* Free Pascal 3
+* Python 2.7 (from [PPA](https://launchpad.net/~deadsnakes/+archive/ubuntu/ppa))
+* Python 3.6
+* Python 3.9 (from [PPA](https://launchpad.net/~deadsnakes/+archive/ubuntu/ppa))
+* Rust (from [Rustup](https://rustup.rs/))
+* Go (from [PPA](https://launchpad.net/~longsleep/+archive/ubuntu/golang-backports))
+* GHC (from [PPA](https://launchpad.net/~hvr/+archive/ubuntu/ghc))
+* C# (from [Mono](https://www.mono-project.com/download/stable/))
+* F# (from [Mono](https://www.mono-project.com/download/stable/))
+
+Each compiler (or interpreter) is available in `$PATH`. It also contains [`testlib.h`](https://github.com/MikeMirzayanov/testlib) in `/usr/include`.
+
+You can download it from [release](https://github.com/syzoj/sandbox-rootfs-ng/releases) or bootstrap by yourself.
+
+# Bootstrapping
+You'll need:
+
+* A Linux box with root privilege
+* `arch-chroot` (usually in the package `arch-install-scripts`)
+* `debootstrap` (some old version of Debian's `debootstrap` couldn't bootstrap Ubuntu 20.04)
+
+First, clone this repo:
+
+```bash
+git clone git@github.com:syzoj/sandbox-rootfs-ng.git
+cd sandbox-rootfs-ng
+```
+
+Set the path to bootstrap rootfs. If there're anything inside it, it'll be `rm -rf`-ed. If the path doesn't exist, it'll be `mkdir -p`-ed.
+
+```bash
+export ROOTFS_PATH=/rootfs-ng
+```
+
+If you're root, just run the `bootstrap.sh` script:
+
+```bash
+./bootstrap.sh
+```
+
+Or if you use `sudo`, remember to preserve the `ROOTFS_PATH` environment variable with `-E` option:
+
+```bash
+sudo -E ./bootstrap.sh
+```
diff --git a/bootstrap.sh b/bootstrap.sh
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+#!/bin/bash
+
+INSTALL_SCRIPT="install.sh"
+
+cd "$(dirname "$0")"
+
+set -e
+
+if [[ "$UID" != "0" ]]; then
+    echo This script must be run with root privileges.
+    exit 1
+fi
+
+if ! arch-chroot -h >/dev/null 2>&1; then
+    echo "You need arch-chroot to run this script."
+    echo "Usually it's in the package "'"'"arch-install-scripts"'".'
+    exit 1
+fi
+
+if ! debootstrap --version >/dev/null 2>&1; then
+    echo "You need debootstrap to run this script."
+    exit 1
+fi
+
+if [[ "$ROOTFS_PATH" == "" ]]; then
+    echo "Please specify the path to put rootfs on with ROOTFS_PATH."
+    exit 1
+fi
+
+if [[ "$MIRROR" == "" ]]; then
+    MIRROR="https://mirrors.tuna.tsinghua.edu.cn/ubuntu"
+fi
+
+rm -rf "$ROOTFS_PATH"
+mkdir -p "$ROOTFS_PATH"
+debootstrap --components=main,universe focal "$ROOTFS_PATH" "$MIRROR"
+
+cp "$INSTALL_SCRIPT" "$ROOTFS_PATH/root"
+arch-chroot "$ROOTFS_PATH" "/root/$INSTALL_SCRIPT"
+rm "$ROOTFS_PATH/root/$INSTALL_SCRIPT"
diff --git a/install.sh b/install.sh
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+#!/bin/bash -e
+
+# Fix PATH environment variable
+export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
+
+# Set Locale
+sed -i 's/# en_US.UTF-8 UTF-8/en_US.UTF-8 UTF-8/' /etc/locale.gen
+locale-gen
+export LC_ALL=en_US.UTF-8
+echo 'LC_ALL=en_US.UTF-8' > /etc/default/locale
+
+# Create sandbox user and directories
+useradd -r sandbox -d /sandbox -m
+mkdir -p /sandbox/{binary,source,working}
+
+# Add focal-updates source
+ORIGINAL_SOURCE=$(head -n 1 /etc/apt/sources.list)
+sed 's/focal/focal-updates/' <<< "$ORIGINAL_SOURCE" >> /etc/apt/sources.list
+
+# Install dependencies
+apt-get update
+apt-get dist-upgrade -y
+apt-get install -y gnupg ca-certificates curl wget locales unzip zip git
+
+# Key: LLVM repo
+wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -
+# Key: Python repo
+apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys BA6932366A755776
+# Key: Go repo
+apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys F6BC817356A3D45E
+# Key: Haskell repo
+apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys FF3AEACEF6F88286
+# Key: Mono repo
+apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+
+# Add sources
+echo "deb http://apt.llvm.org/focal/ llvm-toolchain-focal-11 main" > /etc/apt/sources.list.d/llvm.list
+echo "deb http://ppa.launchpad.net/deadsnakes/ppa/ubuntu focal main" > /etc/apt/sources.list.d/python.list
+echo "deb http://ppa.launchpad.net/longsleep/golang-backports/ubuntu focal main" >  /etc/apt/sources.list.d/go.list
+echo "deb http://ppa.launchpad.net/hvr/ghc/ubuntu focal main" > /etc/apt/sources.list.d/haskell.list
+echo "deb https://download.mono-project.com/repo/ubuntu stable-focal main" > /etc/apt/sources.list.d/mono.list
+
+# Install some language support via APT
+apt-get update
+apt-get install -y g++-10-multilib gcc-10-multilib clang-11 libc++-11-dev libc++abi-11-dev openjdk-11-jdk fpc python2.7 python3.6 python3.9 golang-go ghc mono-devel fsharp
+
+# Install Rust via Rustup
+su sandbox -c "curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y"
+
+# Install Kotlin via SDKMAN!
+su sandbox -c "curl -s https://get.sdkman.io | bash"
+su sandbox -s /bin/bash -c "source ~/.sdkman/bin/sdkman-init.sh && sdk install kotlin"
+
+# Create symlinks for compilers and interpreters with non-common names and locations
+ln -s /usr/bin/g++-10 /usr/local/bin/g++
+ln -s /usr/bin/gcc-10 /usr/local/bin/gcc
+ln -s /usr/bin/clang-11 /usr/local/bin/clang
+ln -s /usr/bin/clang++-11 /usr/local/bin/clang++
+ln -s /sandbox/.sdkman/candidates/kotlin/current/bin/kotlin /usr/local/bin/kotlin
+ln -s /sandbox/.sdkman/candidates/kotlin/current/bin/kotlinc /usr/local/bin/kotlinc
+ln -s /sandbox/.cargo/bin/rustc /usr/local/bin/rustc
+
+# Clean the APT cache
+apt-get clean
+
+# Install testlib
+git clone https://github.com/MikeMirzayanov/testlib /tmp/testlib
+cp /tmp/testlib/testlib.h /usr/include/