Hosts files

Hosts files

dcm keeps its host records in a directory, not in a single file: addn-hosts = /etc/dnsmasq.d/hosts makes dnsmasq load every file in it, which is what lets one page of the UI own one file.

File	Page	Owner	Purpose
hosts/local	Hosts	www-data	LAN hosts, including one entry per cluster node
hosts/vms	Virtual Machines	www-data	virtual-machine records, relocatable between subnets
hosts/isolated	Isolated Hosts	www-data	phone-home endpoints pinned to 127.0.0.1 and ::1

All three are ordinary dnsmasq hosts files — one <ip> <name> record per line, # disables a line. The UI's add, edit, enable/disable and delete actions write exactly that, and lines it does not own (a hand-written comment header, for instance) stay untouched. All three are synced to every node.

hosts/local — and why the nodes belong in it

hosts/local must contain one line per node mapping its hostname to its IP — dcm-cli reads these to generate each node's listen.conf:

192.168.189.1    castor
192.168.189.101  pollux

That is the single source of truth for the listen addresses: no node IP is written into dcm itself, and listen.conf is the one file never copied between nodes — it is regenerated locally after every sync.

hosts/vms — subnet relocation

VMs in hosts/vms keep a fixed last octet across all networks. When the laptop connects to a different network, one click in vms.php replaces all IP prefixes while preserving last octets.

192.168.78.40  iason     →   10.1.10.40  iason
192.168.78.50  orpheus   →   10.1.10.50  orpheus
192.168.78.84  atalante  →   10.1.10.84  atalante
192.168.78.85  hylas     →   10.1.10.85  hylas

(Interim solution: a future version will drop manual relocation and auto-detect the network, so a VM is always reachable by name no matter which connected network it is started in.)

hosts/isolated — quarantined names

Software phone-home endpoints (e.g. the license-check servers of Acronis, Adobe, …) pinned to 127.0.0.1 and ::1 so those lookups fail silently. This is not an ad-blocking list; ad-list blocking is a separate, still-planned feature (see Roadmap).

Both families are needed: a client that gets 127.0.0.1 for an A query but a real address for AAAA still reaches the endpoint. The page therefore shows one row per name set and writes two lines per row, so a name is entered, edited, disabled and deleted once while the file stays a hosts file that can be copied into a system hosts file as it is:

127.0.0.1        activation.acronis.com
::1              activation.acronis.com

The field below the table takes a whole list at once: bare names, one per line, or lines copied straight out of a hosts file, in which case the leading redirect IP and a trailing comment are ignored. Names the file already carries are reported as such instead of being added twice, so pasting a list that contains every name twice — once per family — imports each name once.

A line redirecting to anything other than 127.0.0.1 or ::1 is not dcm's to rewrite: it is listed read-only below the table.

Hosts files versus address=

A hosts file answers per name, and a name it knows wins over an address= line covering the same domain. address= answers a whole domain from one fixed address and belongs to the Fixed Addresses page; since dnsmasq 2.86 it needs a matching local=/domain/ to keep other query types from being forwarded upstream. Both rows are documented in Directive catalog.