These are not really "frequently asked"... it is just a list of stuff that has given us a major headache.
###Q: The container fails to pull down Ubuntu repos and cannot seem to reach the internet
This connectivity issue [1] is fixed with:
sudo apt-get install bridge-utils
pkill docker
iptables -t nat -F
ifconfig docker0 down
brctl delbr docker0
sudo service docker start###Q: On Centos6, I get: "NameError: global name 'DEFAULT_DOCKER_API_VERSION' is not defined"
Centos6 is not supported but a workaround [2] is to yum install python-docker-py.x86_64
###Q: I get: "chpasswd: (user root) pam_chauthtok() failed, error: System error"
This is a kernel bug, according to [3]. Get out of the 3.13 kernel.
###Q: Ceph daemons enter standby mode because they can't grab a resource in /var/lib/ceph
Sometimes docker gets hung up and won't handle the virtual volumes correctly. To fix this:
sudo docker restart###Q: When building a docker image, the container can't reach the internet
Docker doesn't do well behind proxies -- you need to tell it who to ping:
echo "DOCKER_OPTS=\"--dns 15.214.0.20\"" >> /etc/default/docker
sudo service docker restart
```
###Q: When Ansible pulls an image, I get: fatal: [localhost]: FAILED! => {"failed": true, "msg": "module (docker) is missing interpreter line"}
Directory location matters -- make sure to be in the experiment working directory before executing:
```bash
cd roles/hadoop/experiments
ansible-playbook compile.yml###Q: Ansible cannot gather facts, failing on "/bin/lsblk -ln --output UUID /dev/sda1"
Containers running VMs will hang if there are multiple accesses to the block device. This is a known issue that should be solved in Ansible 2.1, where we can specify which facts to gather. For now, run without the emaster/eslave if you are in a VM.
###Q: Docker kills ssh:
We cannot run Docker inside a container -- the following kills all services (Docker, ssh, etc.)
docker stop c0 c1; docker rm d0 c1###Q: It appears SSH hangs
This could be because: (1) it is waiting for a password, (2) you have strict host key checking on, or (3) Travis has slow SSH logins. This can be resolved with --become, host_key_checking=False, and connection=local/connection=ssh, respectively.
[2] ansible/ansible-modules-core#1792
[3] moby/moby#5704
Advantages of Hathisar
- incompatible docker, docker-py, CentoOS versions
- no need to install ansible on the host
- deleting files can use the ANsible modules instead of:
docker exec ceph-mon rm -r /var/lib/ceph/osd
EOF