A GNU Hurd development environment

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I am finally working on Hurd-Projects again. Here I am describing my setup for hacking on the Hurd.

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Setting up a VM

Firstoff: see the setup instructions for qemu. Here I only describe what I need myself.

wget https://cdimage.debian.org/cdimage/ports/latest/hurd-i386/debian-hurd.img.tar.gz
tar -xz < debian-hurd.img.tar.gz

Simple tooling: start the VM and connect to it

I structure my hurd setup into two scripts: run-hurd.sh and login-to-hurd.sh.

start

My Hurd VM is started with ncurses interface to avoid qemu interference with my Keyboard layout. If you use quert*, leave out the --curses.

qemu-system-x86_64 --enable-kvm -m 5G -drive cache=writeback,file=$(echo debian-hurd-*.img) \
  --device rtl8139,netdev=net0 --netdev user,id=net0,hostfwd=tcp:127.0.0.1:10022-:22 --curses

I copied this into the script ./run-the-hurd.sh.

Note the hostfwd: this provides ssh login via port 10022 (copied from the Guix Hurd setup).

login

ssh -p 10022 root@localhost || echo "if ssh cannot connect, 
  run inside the vm 
  ssh arne@192.168.2.105 -p 22 -- cat '~/.ssh/id_rsa.pub' >> ~/.ssh/authorized_keys"

I copied this into the script ./login-to-the-hurd.sh.

Note the error handling: For this to work, you must add your public ssh key to the authorized keys. That provides minimal security.

usage

I start the hurd with

./run-the-vm.sh

Then I login in a second shell with

./login-to-the-hurd.sh

Development tooling

login to and from the VM

I want simple synchronization between VM and Host, so I’m settting up SSH keys on both sides. The ssh-setup for the VM is above. The following allows me to login from the Hurd VM to my host machine:

echo -e "\n\n\n" | ssh root@localhost -p 10022 -- bash -c \
  'ssh-keygen >/dev/null ; cat ~/.ssh/id_rsa.pub' >> ~/.ssh/authorized_keys
echo
ssh root@localhost -p 10022 -- ssh arne@192.168.2.105 echo test

If this prints test, the automatic round-trip works

To avoid using my username and host in here all the time, let’s add aliases.

# host to hurd alias

echo '
Host hurd localhost
    HostName localhost
    User root
    Port 10022
' >> ~/.ssh/config

# hurd to host alias
ssh hurd -- 'cat >> ~/.ssh/config' <<EOF
Host host 192.168.2.105
    HostName 192.168.2.105
    User arne
EOF

ssh hurd -- ssh host echo test

Install the tooling

Mercurial

This is what I use for version control of my own stuff.

mkdir -p ~/Dev
cd ~/Dev
apt install python3-dev
wget https://www.mercurial-scm.org/release/mercurial-5.9.1.tar.gz
tar xf mercurial-5.9.1.tar.gz
cd mercurial-5.9.1
python3 setup.py install --user
echo 'export PATH="${PATH}:${HOME}/.local/bin"' >> ~/.bashrc
source ~/.bashrc

Git

To work with the Hurd git repos. My git install failed initially (didn’t find openssl), so I am using hg-git.

Update: The git install just works with the latest Debian GNU Hurd VM image.

cd ~/Dev
apt install python3-dulwich
hg clone https://foss.heptapod.net/mercurial/hg-git
hg conf --edit # opens with vim:
# - move to the bottom
# - press o to add and edit a line
# - write hggit = ~/Dev/hg-git/hggit
# - write [ui]
# - write username = Your Name <you@example.com>
# - press ESCAPE :wq ENTER to save and exit

Update: After asking on IRC, paulusASol told me a working method to get git:

cd ~/Dev
# get an old snapshot of git-man
wget https://snapshot.debian.org/archive/debian/20210607T032400Z/pool/main/g/git/git-man_2.32.0-1_all.deb
dpkg -i ./git-man_2.32.0-1_all.deb
# install git
apt install git

The Hurd repositories

cd ~/Dev
for i in glibc gnumach hurd incubator libpthread mig procfs unionfs web; do
  # this uses my savannah useraccount. 
  # It needs ~/.ssh/id_rsa.pub added to my account.
  hg clone git+ssh://arnebab@git.savannah.gnu.org:/srv/git/hurd/$i.git;
done

Create a working translator

# get dependencies
apt install autoconf automake mig
# Enter the Hurd translator project
cd hurd/
# build the translators
autoreconf -i
./configure --without-parted
make
# Test the Hello World translator
# -c creates the file.
# Without it, you need to touch the file before.
settrans -c ~/hello $(realpath trans/hello)
cat ~/hello
# Hello, world!
# remove the translator again
settrans -g ~/hello
rm ~/hello

You can replace the translator during development with

settrans -g ~/hello $(realpath trans/hello)

Read the hurd-doc

For convenient access to documentation, install hurd-doc.

apt install hurd-doc

You can then read it with the info-reader of Emacs:

emacs -e info

Type m to choose a topic (i.e. hurd). Use CTRL-x CTRC-c to exit from Emacs. If something goes wrong, hit CTRL-g.

Use CTRL-s inside a topic to search. Repeat CTRL-s for full-text search inside the topic.

Sync with code on the host system for more convenient hacking

# in the Hurd
cd ~/Dev/hurd
hg clone . ssh://host/path/to/hurd-dev
echo "[paths]\ndefault = ssh://host/path/to/hurd-dev" >> .hg/hgrc

Now you can hg pull -u and hg push to sync changes.

You can use any programming tool supported by the host system. Just commit it and pull from the hurd to try it out.

Create a non-root user for testing permissions-stuff

useradd -m user

Start hacking

You have the sources, and you can hack: Ready to try whatever you want to do.