Template values¶

Boxen renders Go templates in write.content and in content loaded by write.contentFromFile or write.contentFromStartupConfig. Use named values with a leading dot, such as {{ .hostname }}. An unknown or unavailable key causes template rendering to fail.

Disk and node values¶

Value	Example	Availability
`.disk`	Vendor disk basename during packaging; `disk.qcow2` at runtime	Both phases
`.version`	`5.16.1`	Both phases, empty if unresolved
`.extraFiles`	`[license.lic baseline.cfg]`	Both phases; list of transferred basenames
`.username`	`admin`	Runtime flag; empty during packaging
`.password`	Node-specific password	Runtime flag; empty during packaging
`.hostname`	`leaf1`	Runtime flag; empty during packaging
`.connectionMode`	Value passed by Containerlab	Runtime flag; empty during packaging

Although .disk contains the source basename during packaging, conversion has already produced the working disk.qcow2 before console steps run. Do not assume the source filename still exists inside the builder.

Index the file list to select one filename:

content: 'echo {{ index .extraFiles 0 }}'

This example writes a command to the guest console. It only works when the guest has access to that file; transferring a companion file into the container does not automatically copy it into the guest.

Management values¶

Value	Example	Meaning
`.mgmtDHCP`	`false`	Boolean selecting guest DHCP configuration
`.mgmtIPv4`	`172.20.20.10/24`	IPv4 address in CIDR notation
`.mgmtIPv4Address`	`172.20.20.10`	IPv4 address without prefix
`.mgmtIPv4PrefixLen`	`24`	Prefix length as a string
`.mgmtIPv4Network`	`172.20.20.0/24`	Masked IPv4 network
`.mgmtIPv4Gateway`	`172.20.20.1`	Default gateway on the management interface
`.mgmtIPv6`	`2001:db8:20::10/64`	Global IPv6 address in CIDR notation
`.mgmtIPv6Address`	`2001:db8:20::10`	IPv6 address without prefix
`.mgmtIPv6PrefixLen`	`64`	Prefix length as a string
`.mgmtIPv6Network`	`2001:db8:20::/64`	Masked IPv6 network
`.mgmtIPv6Gateway`	`2001:db8:20::1`	IPv6 default gateway on the management interface

During packaging and legacy management, IPv4 defaults to 10.0.0.15/24 with gateway 10.0.0.2; IPv6 defaults to 2001:db8::2/64 with gateway 2001:db8::1.

At runtime with transparent management, Boxen reads global addresses and default routes from the container management interface. Missing IPv6 addresses or gateways become empty strings. With transparent DHCP enabled, .mgmtDHCP is true and address-specific keys are absent. Branch on DHCP before accessing them:

write:
  content: |
    {{ if .mgmtDHCP }}
    nv set interface eth0 ipv4 address dhcp
    {{ else }}
    nv set interface eth0 ipv4 address {{ .mgmtIPv4 }}
    {{ if .mgmtIPv4Gateway }}
    nv set interface eth0 ipv4 gateway {{ .mgmtIPv4Gateway }}
    {{ end }}
    {{ if .mgmtIPv6 }}
    nv set interface eth0 ipv6 address {{ .mgmtIPv6 }}
    {{ end }}
    {{ if .mgmtIPv6Gateway }}
    nv set interface eth0 ipv6 gateway {{ .mgmtIPv6Gateway }}
    {{ end }}
    {{ end }}

The exact commands depend on the OS. Use the management guide to choose the networking mode first.

Where rendering happens¶

Templates expand in the text that a write step sends. They do not expand in prompts.response, readUntil matchers, shell hooks, the contentFromFile pathname, or QEMU argument overrides. Static prompt responses should log into the prepared baseline; use runtime write steps for node-specific credentials.

Go template syntax is not shell syntax. Use {{ if ... }} and {{ end }} to guard optional values; avoid accessing a missing management key before the DHCP branch.