Docker container can't resolve DNS to reach another AWS Ec2 Machine - docker

Question

I am not able to ping another machine/host App2 by resolving the DNS from the container running on host App1. Though the /etc/resolv.conf is same as that of host. I am making use of AWS Route 53 private hosted DNS to allow intercommunication by resolving DNS and not IPs.
Some basic info for this :
ubuntu#app1:~$ docker info
Containers: 1
Running: 1
Paused: 0
Stopped: 0
Images: 10
Server Version: 1.13.1
Storage Driver: aufs
Root Dir: /var/lib/docker/aufs
Backing Filesystem: extfs
Dirs: 31
Dirperm1 Supported: false
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host macvlan null overlay
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: aa8187dbd3b7ad67d8e5e3a15115d3eef43a7ed1
runc version: 9df8b306d01f59d3a8029be411de015b7304dd8f
init version: 949e6fa
Security Options:
apparmor
Kernel Version: 3.13.0-106-generic
Operating System: Ubuntu 14.04.5 LTS
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 7.797 GiB
Name: app1
ID: 6GYC:GI6M:JNTM:MMSL:7LRD:BEUZ:RTRD:Q4AG:NEQU:XC5C:ALOK:N3LM
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
WARNING: No swap limit support
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false
############################################
ubuntu#app1:~$ docker version
Client:
Version: 1.13.1
API version: 1.26
Go version: go1.7.5
Git commit: 092cba3
Built: Wed Feb 8 06:42:29 2017
OS/Arch: linux/amd64
Server:
Version: 1.13.1
API version: 1.26 (minimum version 1.12)
Go version: go1.7.5
Git commit: 092cba3
Built: Wed Feb 8 06:42:29 2017
OS/Arch: linux/amd64
Experimental: false
###########################################
ubuntu#app1:~$ docker exec -it conatiner1 sh
/data # ping app2
ping: bad address 'app2'
/data # ping app2.mydomain
PING app2.mydomain (10.xx.xx.xx): 56 data bytes
##############################################
resolv.conf on conatiner
/data # cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 10.xx.xx.xx
search mydomain
resolv.conf on host
ubuntu#app1:~$ cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 10.XX.XX.xx [ same as of container ]
search mydomain
From the docker host i am able to ping App2 wihtout giving full domain like app2.mydomain but same is not working from the container

Answer 1

When you call docker run, please add --net=host option to use host's network stack. It will do the trick.