Update, mention format specifiers

Signed-off-by: Joachim Wiberg <[email protected]>

Author: troglobit

_posts/2024-07-24-setting-hostname.md

@@ -6,23 +6,49 @@ categories: [examples]
 tags: [cli]
 ---
 
-Notice how the hostname in the prompt does not change until the change
-is committed by issuing the leave command.
+A common task for initial setup of your operating system is to change
+the hostname of a device.  The default is a unique name composed from
+the built-in default name suffixed by the last three octets of the base
+MAC address.
+
+```
+admin@infix-c0-ff-ee-:/>
+```
+
+In this example the built-in name is `infix` and the last three octets
+resemble my favorite morning drink.  The built-in name depends on the
+Infix build and can be [tailored to your product][0].
+
+The hostname can be changed from the system configuration context:
 
 ```
-admin@host:/> configure
-admin@host:/config/> edit system
-admin@host:/config/system/> set hostname example
-admin@host:/config/system/> leave
+admin@infix-c0-ff-ee:/> configure
+admin@infix-c0-ff-ee:/config/> edit system
+admin@infix-c0-ff-ee:/config/system/> set hostname example
+admin@infix-c0-ff-ee:/config/system/> leave
 admin@example:/> 
 ```
 
-The hostname is advertised over mDNS-SD in the `.local` domain.  If
-another device already has claimed the example.local CNAME, in our case,
-mDNS will advertise a "uniqified" variant, usually suffixing with an
-index, e.g., `example-1.local`.  Use an mDNS browser to scan for
-available devices on your LAN.
+Notice how the hostname in the prompt does not change until the change
+is committed by issuing the leave command.
+
+There are a few format specifiers available:
+
+ - `%h`: built-in hostname, here `infix`
+ - `%i`: built-in identity, here `infix` (depends on branding)
+ - `%m`: last three octets of base MAC address (may be 00-00-00)
+ - `%%`: literal `%` character
+
+One good reason to maintain a unique hostname, e.g., using `%m`, is that
+it is advertised over mDNS-SD in the `.local` domain.  If another device
+already has claimed the `example.local` CNAME, mDNS will notice this and
+advertise a "uniqified" variant, usually suffixing with an index, e.g.,
+`example-1.local`.  Use an mDNS browser to scan for available devices on
+your LAN.
 
 > Critical services like syslog, mDNS, LLDP, and similar that advertise
 > the hostname, are restarted when the hostname is changed.
 {: .prompt-info }
+
+
+[0]: https://github.com/kernelkit/infix/blob/main/doc/branding.md