boulder: Create README.md

Adds a note on user name spaces.

Signed-off-by: Rune Morling <[email protected]>

boulder/README.md

@@ -0,0 +1,29 @@
+# Boulder
+
+This directory contains the Serpent OS package building tool `boulder`.
+
+## Building boulder
+
+To build boulder, use the `boulder` target:
+
+    cargo build -p boulder
+
+This will produce a debug build by default, which is available as  `./target/debug/boulder`
+
+The [onboarding/ repository](https://github.com/serpent-os/onboarding/) is in the process of being updated to default to building the Rust based boulder.
+
+## Configuring user namespaces
+
+Boulder supports building as your own user, using a feature called "user namespaces".
+
+If your username is `bob` with `UID = 1000` and `GID = 1000` then you will need to add the following files with the following contents:
+
+    $ echo 'bob:100000:65536' |sudo tee /etc/subuid
+    $ echo 'bob:100000:65536' |sudo tee /etc/subgid    
+
+NB: The above assumes you haven't already configured user namespaces.
+
+You can check your username, UID and GID with `grep ${USER} /etc/passwd`, where your username is the first field, the UID is the third field and the GID is the fourth field:
+
+    $ grep ${USER} /etc/passwd
+    bob:x:1000:1000:bob:/home/bob:/bin/bash