diff --git a/Makefile b/Makefile
index 2e97fde..0a30d66 100644
--- a/Makefile
+++ b/Makefile
@@ -78,26 +78,6 @@ print-response-messages:;             cat src/responses/*.cr | ./bin/get-message
 print-response-message-numbers:;      make -s print-response-messages | grep -E "^[0-9]" | sort -n
 print-response-messages-no-comments:; make -s print-response-messages | grep -vE '^[[:blank:]]+#'
 
-# format: nb-domains <TAB> login <TAB> domain1 <TAB> domain2 <TAB> domain3
-MIGRATION_FILE_TARGET = /tmp/dnsmanagerd-migration
-SQLDB = /tmp/usrdb
-POWERDNS_ZONEDIR = /var/powerdns
-BINDDIR = /tmp/DATA-dnsmanagerd/bind9-zones
-$(MIGRATION_FILE_TARGET):; ./bin/sql-to-migration-format.awk < $(SQLDB) > $(MIGRATION_FILE_TARGET)
-run-migration-client:;	./bin/dnsmanager-client admin migration-script $(MIGRATION_FILE_TARGET) $(LOGIN)
-migration-file: $(MIGRATION_FILE_TARGET)
-copy-old-zones: ; cd $(BINDDIR) && for i in * ; do cp -v /tmp/rndczones/$$i . ; done
-/tmp/rndczones:
-	@echo "you forgot to get a copy of old bind zones here: /tmp/rndczones"
-	exit 1
-powerdns-create-zonedir:
-	-mkdir -p $(POWERDNS_ZONEDIR)
-	cp -v $(BINDDIR)/* $(POWERDNS_ZONEDIR)
-powerdns-add-zones: powerdns-create-zonedir
-	cd $(POWERDNS_ZONEDIR) && for i in *; do pdns_control bind-add-zone $$i $(POWERDNS_ZONEDIR)/$$i; done
-migration: build-client migration-file run-migration-client run-client-genzones copy-old-zones
-	@echo "next as root: make powerdns-add-zones"
-
 doc:
 	crystal docs src/main.cr src/client.cr lib/authd/src/client.cr
 
@@ -113,3 +93,5 @@ wipe-db:
 
 release:
 	make build-server OPTS="--release --progress --no-debug"
+
+-include migration.mk
diff --git a/bin/sql-to-migration-format.awk b/bin/sql-to-migration-format.awk
index caacb6e..7c2d5e9 100755
--- a/bin/sql-to-migration-format.awk
+++ b/bin/sql-to-migration-format.awk
@@ -1,5 +1,10 @@
 #!/usr/bin/awk -f
 
+# The input file format should be:
+# login password domain
+#
+# (the "password" field won't actually be used)
+
 BEGIN {
 	OFS = "\t"
 }
diff --git a/migration.mk b/migration.mk
new file mode 100644
index 0000000..167a8d7
--- /dev/null
+++ b/migration.mk
@@ -0,0 +1,62 @@
+# This is the migration makefile.
+#
+# WHAT IS NEEDED FOR THE MIGRATION:
+#
+# - $(SQLDB): a dump of the SQL database (format: login password domain)
+# - $(OLDBINDDIR): directory with old Bind9 zone files
+#
+# HOW MIGRATION WORKS, STEP BY STEP (`migration` rule):
+#
+# 1. build-client         -> build bin/dnsmanager-client
+# 2. migration-file       -> generate $(MIGRATION_FILE_TARGET)
+# 3. run-migration-client -> create users and attribute domains
+# 4. run-client-genzones  -> generate Bind9 zone files with dnsmanagerd
+#                            those files will (mostly) be replaced by the old migrated Bind9 zone files
+# 5. copy-old-zones       -> copies the old Bind9 zone files where dnsmanagerd just produced its Bind9 zone files
+#
+# AFTER THE `migration` RULE: `powerdns-add-zones` as root
+# This will run `pdns_control bind-add-zone domain zonefile` for every zone file in $(POWERDNS_ZONEDIR).
+# Then the different zones should be served by powerdns.
+
+
+# Migration input file, format: login password domain
+SQLDB                 ?= /tmp/usrdb
+
+# Migration final file format: nb-domains <TAB> login <TAB> domain1 <TAB> domain2 <TAB> domain3
+MIGRATION_FILE_TARGET ?= /tmp/dnsmanagerd-migration
+
+# Old Bind9 migrated files.
+OLDBINDDIR            ?= /tmp/rndczones
+
+# Directory where Bind9 zone files are generated by dnsmanagerd.
+BINDDIR               ?= /tmp/DATA-dnsmanagerd/bind9-zones
+
+# Where powerdns reads Bind9 zone files.
+POWERDNS_ZONEDIR      ?= /var/powerdns
+
+$(MIGRATION_FILE_TARGET):
+	./bin/sql-to-migration-format.awk < $(SQLDB) > $(MIGRATION_FILE_TARGET)
+
+run-migration-client:
+	./bin/dnsmanager-client admin migration-script $(MIGRATION_FILE_TARGET) $(LOGIN)
+
+copy-old-zones:
+	cd $(BINDDIR) && for i in * ; do cp -v $(OLDBINDDIR)/$$i . ; done
+
+$(OLDBINDDIR):
+	@echo "you forgot to get a copy of old bind zones here: $(OLDBINDDIR)"
+	exit 1
+
+# A nice rule for the command-line.
+migration-file: $(MIGRATION_FILE_TARGET)
+
+migration: build-client migration-file run-migration-client run-client-genzones copy-old-zones
+	@echo "next as root: make powerdns-add-zones"
+
+# POWERDNS RULES
+powerdns-create-zonedir:
+	-mkdir -p $(POWERDNS_ZONEDIR)
+	cp -v $(BINDDIR)/* $(POWERDNS_ZONEDIR)
+
+powerdns-add-zones: powerdns-create-zonedir
+	cd $(POWERDNS_ZONEDIR) && for i in *; do pdns_control bind-add-zone $$i $(POWERDNS_ZONEDIR)/$$i; done