Of course, it is possible to download the agents for Linux/Windows/etc, not only via the browser but also by getting them via wget and the REST API.
Prerequisites needed: a user with sufficient rights (the automation user would do out of the box), Checkmk's server hostname (or IP), the site which holds the agent, and the agent you want to download (i.e., OS & hash).
The easiest way for the latter is to navigate to the Agents section in Checkmk and hover the cursor over the installation package:
If you're not able to fetch the hash via the browser, you can access it via CLI:
root@linux# su - mysite OMD[mysite]:~$ ls var/check_mk/agents/linux_deb/packages/ 1ae46a9ab42f290b 1ae46a9ab42f290b.conf 1ae46a9ab42f290b.sig 8107877152463cf2 8107877152463cf2.conf 8107877152463cf2.sig
wget
As you can see, the HTTP call in the above screenshot is almost complete, so you can right-click on the package and say (depending on the browser): "Copy link" and then create the wget link out of it:
wget "http(s)://<checkmkhost>/<site>/check_mk/download_agent.py?hostname=<hostname>&hash=c9394c3914cc6982&os=linux_tgz&_username=automation&_secret=<automation_secret>" -O agent.deb
httpie, download by the hash value
Install httpie on the system where you want to download the agent.
Create a script with the following content:
#!/bin/bash HOST_NAME="<checkmk_server>" SITE_NAME="<sitename>" API_URL="http://$HOST_NAME/$SITE_NAME/check_mk/api/1.0" USERNAME="automation" PASSWORD="<automation_secret>" http --json GET "$API_URL/domain-types/agent/actions/download_by_hash/invoke" \ "Authorization: Bearer $USERNAME $PASSWORD" \ "Accept: application/octet-stream" \ agent_hash=="<hash<"\ os_type=="linux_deb" \ --download
httpie, download by hostname
Create a script with the following content (host_name in the third section means the host for which the agent is for):
#!/bin/bash HOST_NAME="<checkmk_server>" SITE_NAME="<sitename>" API_URL="http://$HOST_NAME/$SITE_NAME/check_mk/api/1.0" USERNAME="automation" PASSWORD="<automation_secret>" http --json GET "$API_URL/domain-types/agent/actions/download_by_host/invoke" \ "Authorization: Bearer $USERNAME $PASSWORD" \ "Accept: application/octet-stream" \ host_name=="localhost"\ os_type=="linux_deb" \ --download