---
last_review: "2025-01-01"
last_reviewer: "-"
documented_code: [ ]
---

```{tags} explanation, developer, how-to
```

# Development and debugging rules, tips and tricks #

:::{note}
This page has been migrated from the old documentation, and has not yet been fully revised.
There might be inconsistencies or errors when using with current LinkAhead versions.
:::
% TODO: Issue: https://gitlab.indiscale.com/caosdb/src/linkahead-docs/-/issues/100
% TODO: Move non-explanation parts to Tutorial or How-To

## Connecting to containers and services ##

- Start a shell inside the LinkAhead container: `docker exec -ti linkahead /bin/bash`
    - As root: `docker exec --user 0:0 -ti linkahead /bin/bash`
- Connect to the SQL database (from inside the caosdb-server container):
  `mariadb -h sqldb -u caosdb -prandom1234 caosdb`
    - If you want to transfer 4-byte characters (e.g. Chinese or emojis), add the option
      `--default-character-set=utf8mb4`
    - A combined command: `docker exec -ti linkahead mariadb -h sqldb -u caosdb -prandom1234 caosdb`

## Setting up a Debian caching proxy for apt ##

A proxy which caches access to the apt repositories can speed up Docker building a lot, especially
on slow an/or unreliable internet connections.

LinkAhead by default looks for an HTTP proxy server running on the Docker host which listens on port
8123.

**Developer's note:** We chose port 8123 in order to keep the default port 8000 free for other
applications which use it by default.

### Squid ###

An easy way to set up a server is to use Squid, especially with the default settings as packaged on
Debian and Ubuntu in the `squid-deb-proxy` package: `apt install squid-deb-proxy`

After installation, edit `/etc/squid-deb-proxy/squid-deb-proxy.conf` and change the port to `8123`.

If you are paranoid, you may restrict the allowed networks to `172.17.0.0/24` in
`/etc/squid-deb-proxy/allowed-networks-src.acl`.