How can you set multiple hosts on the same machine with dynamic inventories

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1

Hi,

I’m currently setting up two VMs that are accessible behind a single domain name but on different ports. I cannot figure
out how to specifiy host-vars seperately for each host. My aim is to allow ansible to SSH into each of these machines; I’m not currently
using hostvars for anything else.

If I had two machines accessible on different ports and different domains - example-1.com:22 and example-2.com:9001 - I would produce this dynamic inventory JSON output:

{ "mymachines": { "hosts": [ "example-1.com", "example-2.com" ], "hostvars": { "example-1.com": { "ansible_port": "22" }, "example-2.com": { "ansible_port": "9001" } } } }

However, there is no analogue for different hosts with the same domain name:

{ "mymachines": { "hosts": [ "example-0.com", "example-0.com", ], "hostvars": { "example-0.com": { "ansible_port": "22" }, ??: { "ansible_port": "9001" } } } }

I cannot specify the domain-names alongside their ports
`

{
“mymachines”: {
“hosts”: [
“example-0.com:22”,
“example-0.com:9001”,
]
}
}
`

as Ansible passes the entire host to OpenSSH without using the -p argument, which means the host never resolves. It seems
to run code equivalent to the following

ssh foo@example-0.com:9001 # BAD

not

ssh foo@example-0.com -p 9001 # GOOD

Do you have any advice for how I can create a dynamic inventory that allows SSH access to machines with the same domain name
but different ports? I’ll post more information if needed.

Thanks

2

Just as with ini formatted inventories, if you want to use the same IP or hostname for 2 different “hosts”, you need to create an alias for them, and specify the hostname using ansible_host (ansible_ssh_host for versions before v2)

3

Thanks for your (quick!) suggestion. That worked perfectly, thank you. For reference by anyone reading this question, the working solution looks roughly like this:

{ "example-1": { "vars": { "ansible_host": "example-1.com", "ansible_port": 5513 }, "hosts": [ "unused-alias-1" ] }, "example-2": { "vars": { "ansible_host": "example-2.com", "ansible_port": 22 }, "hosts": [ "unused-alias-0" ] } }

4

Are you sure that’s quite right? I’d have expected the “ansible_host” value within each host entry to be the same, otherwise you wouldn’t have had the problem in the first place…?

5

Sorry, thanks for catching that error. I attached an amended version:

{
“alias-1”: {
“vars”: {
“ansible_host”: “example-0.com”,
“ansible_port”: 5513
},
“hosts”: [
“unused-alias-1”
]
},
“alias-2”: {
“vars”: {
“ansible_host”: “example-0.com”,
“ansible_port”: 22
},
“hosts”: [
“unused-alias-0”
]
}
}