Reorganize documentation for new website (#213)

This PR should be merged after the new website is deployed.

- [x] Rename files
- [x] Add front matter section to all `.md` files in the book (necessary for Zola)
- [x] Change all internal links to use Zola's linking system that checks broken links
- [x] Some updates to documentation contents and organization

Co-authored-by: Alex Auvolat <alex@adnab.me>
Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/213
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>

1 files changed, 53 insertions, 0 deletions

diff --git a/doc/book/cookbook/systemd.md b/doc/book/cookbook/systemd.md
new file mode 100644
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+++ b/doc/book/cookbook/systemd.md
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++++
+title = "Starting Garage with systemd"
+weight = 15
++++
+
+We make some assumptions for this systemd deployment. 
+
+  - Your garage binary is located at `/usr/local/bin/garage`.
+
+  - Your configuration file is located at `/etc/garage.toml`.
+
+  - Your `garage.toml` must be set with  `metadata_dir=/var/lib/garage/meta` and `data_dir=/var/lib/garage/data`. This is mandatory to use `systemd` hardening feature [Dynamic User](https://0pointer.net/blog/dynamic-users-with-systemd.html). Note that in your host filesystem, Garage data will be held in `/var/lib/private/garage`.
+
+
+
+Create a file named `/etc/systemd/system/garage.service`:
+
+```toml
+[Unit]
+Description=Garage Data Store
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Environment='RUST_LOG=garage=info' 'RUST_BACKTRACE=1'
+ExecStart=/usr/local/bin/garage server
+StateDirectory=garage
+DynamicUser=true
+ProtectHome=true
+NoNewPrivileges=true
+
+[Install]
+WantedBy=multi-user.target
+```
+
+*A note on hardening: garage will be run as a non privileged user, its user id is dynamically allocated by systemd. It cannot access (read or write) home folders (/home, /root and /run/user), the rest of the filesystem can only be read but not written, only the path seen as /var/lib/garage is writable as seen by the service (mapped to /var/lib/private/garage on your host). Additionnaly, the process can not gain new privileges over time.*
+
+To start the service then automatically enable it at boot:
+
+```bash
+sudo systemctl start garage
+sudo systemctl enable garage
+```
+
+To see if the service is running and to browse its logs:
+
+```bash
+sudo systemctl status garage
+sudo journalctl -u garage
+```
+
+If you want to modify the service file, do not forget to run `systemctl daemon-reload`
+to inform `systemd` of your modifications.