Docker Container not use host DNS - docker

Question

i'm used custom docker network named "backend-network"
[root#localhost docker]# docker inspect backend-network
{
"Name": "backend-network",
"Id": "18180c0c1ef14460a25b66b7fb971e090f7bb85f549921704d11937af70766c7",
"Created": "2018-08-07T12:36:02.4175991+09:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "172.18.0.0/16",
"Gateway": "172.18.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Containers": {
"531c1ecbe993ee13e632fbd9697b392ee989d756ff60c07eae96a700901aaa01": {
"Name": "splash",
"EndpointID": "c9e4e7ec319ecf9cdcbb9ca50170efb63c4fca33bcbbabb584c4a4e41576b15d",
"MacAddress": "02:42:ac:12:00:05",
"IPv4Address": "172.18.0.5/16",
"IPv6Address": ""
},
"c6a5aa827e901b6b6d7b35d4a8be5a5b2fc73f1a7a385416ce200e847d400b21": {
"Name": "flask",
"EndpointID": "5d5abb3bc964d251379a7f6a84cb5b5d9bddac9b778f2222d52aba657b28dd34",
"MacAddress": "02:42:ac:12:00:02",
"IPv4Address": "172.18.0.2/16",
"IPv6Address": ""
},
"da839143fb58d738e38922c669efa332c545fee4dd0a5b733583ed7b8df60875": {
"Name": "django",
"EndpointID": "f046e9cc93f895b12ce1c4de983fbe0e54a3904460c04db3ba238ba84ba82327",
"MacAddress": "02:42:ac:12:00:03",
"IPv4Address": "172.18.0.3/16",
"IPv6Address": ""
},
"fc9e6ef183c81a3fe7dd29ecb5c17c0dc27fb803ef8e214d4f344a2b3407ec54": {
"Name": "mongo",
"EndpointID": "ab94182f4b175f105ab01ccbbc43b7dad37cf5506eee831168fd5bd9094ccde8",
"MacAddress": "02:42:ac:12:00:04",
"IPv4Address": "172.18.0.4/16",
"IPv6Address": ""
}
},
"Options": {},
"Labels": {}
}
But each Container not used host DNS.
host DNS is.
[root#localhost docker]# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 192.168.88.1
and container DNS is
(django) root#da839143fb58:/opt/django_backend/scrapy_app# cat /etc/resolv.conf
nameserver 127.0.0.11
options ndots:0
i added
nameserver 192.168.88.1
container's resolv.conf, and it works but request too long.
I think first search in
nameserver 127.0.0.11
and search
nameserver 192.168.88.1
how can i set docker-network to host dns?
remove
nameserver 127.0.0.11
then don't communicate other container by name. like
(django) root#da839143fb58:/opt/django_backend/scrapy_app# ping splash
ping: splash: Name or service not known

Answer 1

Docker containers are resolving DNS requests through embedded DNS server (this is the IP you are seeing in the container's /etc/resolv.conf – see bottom note in documentation). Depending on your configuration the embedded DNS server forwards the query to your host (default) or another DNS-server. You can pass a custom DNS server with the --dns- flag.
Please find more information about that in the documentation.