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# 1. Introduction

Starting from VS Code release 1.99, some servers (such as white, black and red who fail the requirements, including glibc >= 2.28 and libstdc++ >= 3.4.25) can not be accessed through VS Code remotely. The official provides a temporary patch to fix this, though an annoying banner is still present.

To make it short, software `crosstool-ng` can generate a directory `sysroot` containing library file needed. Then `patchelf` can help VS Code server consume the required files during the installation process. Finally a script `sysroot.sh` can tell VS Code and patchelf where to find all those file. 

First, I will show users how to set up. Next, I will show what I have done for those who are interested.

# 2. Usage

For users, what they need to do is just adding those lines to their .bashrc or .cshrc file.
```
# Patchelf / VS Code
source /home/usr/share/sysroot/sysroot.sh
```
or
```
# Patchelf / VS Code
source /home/usr/share/sysroot/sysroot.csh
```

That's all if you are a user. For developers, the next chapter may be helpful.

# 3. Configuration

- The main instruction: [修复 远程主机不满足运行VS Code服务器的先决条件](https://remrin.xlog.app/vscode-remote-fix)
- The repo used: [GitHub - ursetto/vscode-sysroot](https://github.com/ursetto/vscode-sysroot)
- Official version: [Remote Development FAQ](https://code.visualstudio.com/docs/remote/faq#_can-i-run-vs-code-server-on-older-linux-distributions)

## 3.1. Install crosstool-ng
[crosstool-NG](https://crosstool-ng.github.io/docs/) is a tool to generate required library files `sysroot`
```
sudo apt-get update
sudo apt-get install -y gcc g++ gperf bison flex texinfo help2man make libncurses5-dev python3-dev autoconf automake libtool libtool-bin gawk wget bzip2 xz-utils unzip patch rsync meson ninja-build

wget http://crosstool-ng.org/download/crosstool-ng/crosstool-ng-1.26.0.tar.bz2
tar -xjf crosstool-ng-1.26.0.tar.bz2
cd crosstool-ng-1.26.0
./configure --prefix=/home/usr/share/crosstool-ng 
make
make install
```

## 3.2. Generate sysroot
`sysroot` is a directory containing required library files.

```
sysroot/
├── etc
├── lib
├── lib64 -> lib
├── sbin
├── sysroot.sh
├── usr
└── var
```

Maybe you shall remove some experiment variables first, such as `LD_LIBRARY_PATH`, otherwise some unexpected errors.
```
mkdir toolchain-dir
cd toolchain-dir
# download the config file from https://github.com/ursetto/vscode-sysroot/blob/main/x86_64-gcc-8.5.0-glibc-2.28.config
cp x86_64-gcc-8.5.0-glibc-2.28.config .config
ct-ng build
```
The directory `x86_64-linux-gnu/x86_64-linux-gnu/sysroot` is what we needed. For the file `.config`, what's different from the official version are two variables `CT_LINUX_VERSION` and `CT_GLIBC_MIN_KERNEL`. Microsoft set them to `4.19.287`, while they shall be `3.10` for Centos 7. For Ubuntu 18.04 with kernel version `4.15.0`, `3.10` works.

## 3.3. Download patchelf
[patchelf](https://github.com/NixOS/patchelf) is a software to help VS Code server to find related library files. The binary file itself works well. I put it into `sysroot`, following `ursetto`'s instruction. Some steps are necessary due to file permission problems.

```
cd x86_64-linux-gnu/x86_64-linux-gnu/sysroot/usr
chmod 755 bin
cd bin

# download binary file from https://github.com/NixOS/patchelf/releases/download/0.18.0/patchelf-0.18.0-x86_64.tar.gz
tar -xvf patchelf-0.18.0-x86_64.tar.gz
cp patchelf-0.18.0/bin/patchelf ./

cd ..
chmod -R 555 bin
```

## 3.4. Add a source file
This is a script for use's convenience. It defines three variables to help VS Code to find the files. I put the script in `sysroot`

`sysroot.sh`
```sh
# Path to the dynamic linker in the sysroot (used for --set-interpreter option with patchelf)
export VSCODE_SERVER_CUSTOM_GLIBC_LINKER=/home/usr/share/sysroot/lib/ld-linux-x86-64.so.2
# Path to the library locations in the sysroot (used as --set-rpath option with patchelf)
export VSCODE_SERVER_CUSTOM_GLIBC_PATH=/home/usr/share/sysroot/usr/lib:/home/usr/share/sysroot/lib
# Path to the patchelf binary on the remote host
export VSCODE_SERVER_PATCHELF_PATH=/home/usr/share/sysroot/usr/bin/patchelf
```
`sysroot.csh`
```csh
# Path to the dynamic linker in the sysroot (used for --set-interpreter option with patchelf)
setenv VSCODE_SERVER_CUSTOM_GLIBC_LINKER /home/usr/share/sysroot/lib/ld-linux-x86-64.so.2
# Path to the library locations in the sysroot (used as --set-rpath option with patchelf)
setenv VSCODE_SERVER_CUSTOM_GLIBC_PATH /home/usr/share/sysroot/usr/lib:/home/usr/share/sysroot/lib
# Path to the patchelf binary on the remote host
setenv VSCODE_SERVER_PATCHELF_PATH /home/usr/share/sysroot/usr/bin/patchelf
```

```
cd ../..
chmod 755 sysroot
vi sysroot/sysroot.sh
vi sysroot/sysroot.csh
chmod 555 sysroot
```

## 3.5. Something special
Finally, I move `sysroot` to a public directory.
```
rsync -avz toolchain-dir/x86_64-linux-gnu/x86_64-linux-gnu/sysroot/ /home/usr/share/sysroot
chown -R xuelab:xue /home/usr/share/sysroot
```

For users, they need to add those lines to their .bashrc or .cshrc file.
```
source /home/usr/share/sysroot/sysroot.sh
source /home/usr/share/sysroot/sysroot.csh
```
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