add documentation for mirror selection

1 files changed, 23 insertions, 0 deletions

diff --git a/doc/examples/cloud-config.txt b/doc/examples/cloud-config.txt
index 73a5e099..db37fc4b 100644
--- a/doc/examples/cloud-config.txt
+++ b/doc/examples/cloud-config.txt
@@ -17,7 +17,30 @@ apt_upgrade: true
 #
 # Default: auto select based on cloud metadata
 #  in ec2, the default is <region>.archive.ubuntu.com
+# apt_mirror:
+#   use the provided mirror
+# apt_mirror_search:
+#   search the list for the first mirror.
+#   this is currently very limited, only verifying that
+#   the mirror is dns resolvable or an IP address
+#
+# if neither apt_mirror nor apt_mirror search is set (the default)
+# then use the mirror provided by the DataSource found.
+# In EC2, that means using <region>.ec2.archive.ubuntu.com
+# 
+# if no mirror is provided by the DataSource, then search
+# for dns names '<distro>-mirror' in each of
+# - fqdn of this host per cloud metadata
+# - localdomain
+# - no domain (which would search domains listed in /etc/resolv.conf)
+# That gives the cloud provider the opportunity to set mirrors of a distro
+# up and expose them only by creating dns entries.
+#
+# if none of that is found, then the default distro mirror is used
 apt_mirror: http://us.archive.ubuntu.com/ubuntu/
+apt_mirror_search: 
+ - http://local-mirror.mydomain
+ - http://archive.ubuntu.com
 
 # Preserve existing /etc/apt/sources.list
 # Default: overwrite sources_list with mirror.  If this is true