cea/readme: Update information with examples

Refs. sysadm-environment#5367

cea/Readme.md

@@ -57,8 +57,23 @@ For example: `BOOT_DISK_ID_PATTERN: wwn-0x600063B40DD553802E296F4A1DB5BC1F`
 
 ### Preseed generation
 
+For the following part, we'll be working on a node to setup called $NODE.
+For example:
+
+```
+$ NODE=balin024
+```
+
 1. Create a yaml file with the server properties in the ``configs`` directory
 
+    For example:
+
+```
+$ head -3 cea/configs/$NODE.yaml
+---
+HOSTNAME: balin024
+```
+
 2. Set the passwords in `root_passwords` and `swh_passwords` files with the
    respective values in the credential store
 
@@ -66,13 +81,19 @@ For example: `BOOT_DISK_ID_PATTERN: wwn-0x600063B40DD553802E296F4A1DB5BC1F`
    the post install script in the `preseeding` and `preseeding/finish_install`
    directories
 
+   For example:
+
+```
+./cea/build_preseed.sh $NODE
+```
+
 4. Transfer the `preseeding` directory on the bastion in the directory
    `/var/www/html/preseeding`
 
    For example:
 
 ```
-rsync -avP configs/preseeding swh@angrenost:/var/www/html/
+rsync -avP ./cea/configs/preseeding swh@angrenost.internal.cea.swh.network:/var/www/html/
 ```
 
 5. Reboot the server with a <network card> IPV4 PXE boot device (**not IPV4