I have a hostname with dots and dashes. I need to use that hostname as the service name.
Suppose My hostname is Prasanna.abc.in. I want to make that hostname as a service name in the docker stack file.
Docker allows you to create a service with a "DNS name component". That's alpha numeric with dashes, and up to 63 characters. See the hostname spec on wikipedia. This does not let you use underscores or dots in the name since that is not a hostname component (dots are used to separate multiple components and underscores would be invalid).
For a FQDN, consider using a label on your service instead. You'll be able to give that label the full value of the hostname, and query by that label.
Related
I have an AWS load balancer. AWS assigns a DNA name like:
data-vm-190.eu-west-1.elb.amazonaws.com
When I try to create a DNS CNAME record in Google Cloud, I get this error:
"Record data must be in the format server-1.example.com"
How can I get past this?
The solution is to append a dot (.) to the record name.
Adding a dot (period or .) at the end of a domain name declares a fully qualified domain name. Without the trailing dot, some DNS servers will treat the name as relative to the zone name.
In the hierarchy of the domain name system, the root servers are named .. The domain com is a child of the root servers. The fully qualified name for com is com.. Popular usage dropped the trailing root servers (dropped the .) but DNS still treats that character as important.
I am looking at the stackstorm docker-compose file, and within it almost all containers have a line dns_search: . According to docker-compose documentation, dns_search is for the purpose of configuring search domains.
I am used to seeing this in context of transparently adding a domain to unqualified short domains. For example if I add dns_search: mydomain.com, I would expect "host1" to transparently resolve as "host1.mydomain.com".
I have never seen this set as a single dot . before. What is the effect/purpose of doing this configuration?
I'm posting the answer from the Stackstorm Git project issue see comment/"dns_search: .". Paraphrasing: it was useful in old versions of Docker before 2017, before the ndots configuration was available. Nowadays that configuration has no impact, and in fact has been removed from the stackstorm docker-compose file.
I believe this is because all domain names end in . under the hood, but browsers and other software abstracts this out.
For example. under the hood www.google.com is actually www.google.com.
So, in the docker-compose file, this would essentially be saying "Find me any domain"
A bit more detail on why there's an extra dot, if you're interested:
Domain name resolution is heirachical, reading right to left, with each block, separated by a ., being a step in the process. A DNS resolver will first find a source of ., which will be able to return the address for a resolver for the next block, until it reaches the final block, where it returns the full DNS record.
Extending EdwardTeach's answer:
#ytjohn effectively said they did in the past because putting dns_search: . configures the DNS search domains to be only . instead of inheriting the host ones. I can't confirm that because I didn't test it.
Now, I tested what docker-compose does today, and in a container, cat /etc/resolve.conf returns:
nameserver 127.0.0.11
options ndots:0
Where options ndots:0 is (from resolv.conf docs):
ndots:n
Sets a threshold for the number of dots which must
appear in a name given to res_query(3) (see
resolver(3)) before an initial absolute query will
be made. The default for n is 1, meaning that if
there are any dots in a name, the name will be
tried first as an absolute name before any search
list elements are appended to it. The value for
this option is silently capped to 15.
With ndots:0, all domains will be attempted using the absolute name first, only then using the search list.
How I came to this conclusion
The Github comment:
If you don't set this dns_search: ., then whatever the host has in search in their /etc/resolv.conf will get put into your container's /etc/resolv.conf.
This doesn't happen. My host has search domain[0]: broadband (macOS command: scutil --dns), and in docker containers, it doesn't show broadband (linux command: cat /etc/resolv.conf). Instead, it says options ndots:0
dns_search docs:
dns defines custom DNS search domains to set on container network interface configuration. Can be a single value or a list.
What is a DNS search domain?
It is the DNS service used to resolve hostnames that are not fully qualified, e.g. hostname will try hostname.example.com then hostname.website.com if your search domains list was example.com, website.com. More information on https://superuser.com/a/184366
In another repo (crossdock), their dockerfile had the comment:
`dns_search: . # Ensures unified DNS config.`
I'm attempting to put my AD domain credentials into the YAML config file created by rancher so that I may use vSphere storage within Rancher / Kubernetes, however, I'm running into an issue with the formatting of the virtual_center config portion:
(...)
virtual_center:
<IP>:
(...)
user: "DOMAIN/username"
password: <PASSWORD>
The cluster doesn't seem to like a backslash (or two backslashes including the escape character), and it also doesn't seem to like a forward slash.
How should I enter my domain credentials in here?
EDIT
nvm, i figured it out.
JK, answer below.
Apparently the solution is to use a user#domain.site.local format rather than a DOMAIN\user format.
See:
https://github.com/rancher/rancher/issues/16371
I'm a newbie in domain names, DNS etc.
I'm using surge.sh for deploying my app. Now I want to add a custom domain, that I registered using transIP, and I can't get it working. I set the IP address to 45.55.110.124, as they explain here. All together, I entered the following settings:
Name: *
TTL: 1 min
Type: A
Address: 45.55.110.124
And another one, exactly the same but then using name #:
Name: #
TTL: 1 min
Type: A
Address: 45.55.110.124
I created a test page that contains hello domain, inside a simple html file. Now, I deployed the page by moving to the folder that contains the html file and doing: surge ./ mydomain.io.
I waited over 5 minutes and nothing is changing.
Now, my questions are:
What am I doing wrong?
My domain provider suggests that I also use an IPv6 address, but which one should I use for Surge?
Why is there an option of setting TTL longer than 1 minute, who wants to wait longer before their deploy comes online?
For starters, you want to use the CNAME instead of A record if possible. The reason for this is that their IP address can possibly change out from under you when infrastructure changes / updates / re-deploys. If possible, remove the A records and create CNAME records pointing to na-west1.surge.sh. instead.
Next, assuming that they want you to point to the same IP as na-west1.surge.sh resolves to, that IP is different from the documentation (possible even due to my previous explanation). You can ping the domain or use the host utility to get the current IP address:
$ host na-west1.surge.sh
na-west1.surge.sh has address 138.197.235.123
Armed with this information, try changing to CNAME records first. If this isn't possible, then use the updated IP address that you get from resolving the their CNAME.
I am trying to start a google compute engine (GCE) instance with a pre-configured FQDN. We are intending to run an application that is licensed based on the contents of /etc/hosts.
I am starting the instances using the Google Cloud SDK utility - gcloud.
I have tried setting the "hostname" key using the metadata option like so:
gcloud compute instances create mynode (standard opts) --metadata hostname=mynode.example.com
Whenever I log into the developer console, under computer, instances, I can see hostname under "Custom metadata". This appears to be a new, custome key - it has no impact on what:
http://metadata.google.internal/computeMetadata/v1/instance/hostname
returns.
I have also tried setting "instance/hostname" like the below, which causes a parsing error when using gcloud.
--metadata instance/hostname=mynode.example.com
I have successfully used the startup scripts functionality of the metadata server to run a startup script that parses the new, internal IP address of the newly created instance, updated /etc/hosts. This appears to work but doesn't feel "like the google way".
Can I configure the FQDN (specifically, a domain name, as the instance name is always the hostname) of an instance, during instance creation, using the metaserver functionality?
try this:
Go to your GCE >> VM instances panel.
stop your gce instance.
clic on the instance name.
Edit your instance, adding this values on Custom metadata fields:
Key field: hostname / Value field: your.server.hostname
Key field: startup-script / Value field: sudo -s hostnamectl set-hostname your.server.hostname
setup-example-image.png
Finally, start your instance and test with a hostnamectl command.
regards!
According to this article 'hostname' is part of the default metadata entries that provide information about your instance and it is NOT possible to manually edit any of the default metadata pairs. You can also take a look at this video from the Google Team. Within the first few minutes it is mentioned that you cannot modify default metadata pairs. As such, it does not seem like you can specify the hostname upon instance creation other than through the use of a start-up script like you've done already. It is also worth mentioning that the hostname you've specified will get deleted and auto-synced by the metadata server upon reboot unless you're using a start-up script or something that would modify it every time.
If what you're currently doing works for what you're trying to accomplish, it might be the only workaround to your scenario.
Here is a patch for /usr/share/google/set-hostname to set FQDN to GCE instance.
https://gist.github.com/yuki-takeichi/3080521322f0f1d159ea6a343e2323e6
Before you use this patch, you must set your desired FQDN in your instance's metadata by specifying hostname key.
Hostname is set each time instance's IP address is renewed by dhclient. set-hostname is just a hook script which dhclient executes and serves new IP address and internal hostame to, and modifies /etc/hosts. This patch changes the source of hostname by querying instance's metadata from metadata server.
The original set-hostname script is here:
https://github.com/GoogleCloudPlatform/compute-image-packages/blob/master/google_config/bin/set_hostname.
Use this patch at your own risk.
When creating a VM, you can specify a custom FQDN hostname as an optional parameter. This feature is currently in Beta.
$ gcloud beta compute instances create INSTANCE_NAME --hostname example.hostname
This should work across OSes, and eliminate the need for workaround scripts.
More info in the docs.
-- Sirui (Product Manager, Google Compute Engine)
I've looked throughout this site to find answered questions and found a few things that work but with a couple solutions combined. This thread seems the place to answer.
1) echo example.com > /etc/hostname
2) add -- 127.0.1.1 example.com in /etc/hosts
3) add -- hostnamectl set-hostname
example.com -- command to /etc/rc.local script
4) uncomment /etc/dhcp/dhclient.conf line:
supersede domain-name "example.com";
5) profit.... Seems to stick after each reboot
(Note example.com is your domain name: fqdndomain.com - yourfqdndomain.org)
Also note this is for Ubuntu or Debian. Other Unix May slightly vary. I've tested this on Ubuntu 16.04
Always on the wording NOT possible to manually edit any of the default metadata pairs, how about the instant level default metadata "/scheduling"? we could set them manually as mentioned in this article