docs: add CLI package manager detection note

[Copilot]

The CLI preflight flow could not reliably proceed on newer or unrecognized Linux distributions because OS detection relied only on /etc/os-release. The update documents the new compatibility-mode behavior that probes package managers and warns about support boundaries.

• Documentation updates
  • Add a new “Command Line Tool” section in the 1.11.0 important notes covering package manager probing and compatibility warnings, with links to the related CLI PR and issue.

Example note excerpt:

Longhorn v{{< current-version >}} improves the Longhorn command-line tool by attempting to detect common package managers ... The CLI warns that the operating system is not officially supported and proceeds in a compatibility mode ...

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[FEATURE] Guess Linux distro from the package manager</issue_title>
<issue_description>### Is your feature request related to a problem? Please describe (👍 if you like this request)

Currently to Longhorn CLI and node controller, it detect the platform from the os-release file and compare with a fixed list of keywords. However, there is still some chance to check the dependencies on such platform by detecting the supported package manager commands.

Describe the solution you'd like

If os-release does not matches any of the listed OS keyword, given a list of package manager commands:

• zypper for SUSE-based distros
• transactional-update for SUSE micro
• apt for DEB distros
• yum or dnf or microdnf for RPM distros
• pacman for Arch Linux family

If the command is available, warn the user for the risk of compatibility, and then check the environment using the detected package manager.

Describe alternatives you've considered

No response

Additional context

No response</issue_description>

<agent_instructions>Review the ticket and add a "Command Line Tool" section after the "Access Mode Supportability" section in the important note https://github.com/longhorn/website/blob/master/content/docs/1.11.0/important-notes/_index.md and add an important note for the improvement.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@derekbit @NamrathShetty Could we assign the ticket to you because you are working on the improvement? Thanks. @derekbit @roger-ryao Can you test OpenEurler as well? @yangchiu Tested on master-head (longhorn/cli 63745e4). `longhornctl` fails to run on `sle-micro 6.1`:

~> cat /etc/os-release 
NAME="SL-Micro"
VERSION="6.1"
VERSION_ID="6.1"
PRETTY_NAME="SUSE Linux Micro 6.1"
ID="sl-micro"
ID_LIKE="suse sle-micro opensuse-microos microos"
ANSI_COLOR="0;32"
CPE_NAME="cpe:/o:suse:sl-micro:6.1"
HOME_URL="https://www.suse.com/products/micro/"
DOCUMENTATION_URL="https://documentation.suse.com/sl-micro/6.1/"
LOGO="distributor-logo"

$ ./longhornctl-linux-amd64 install preflight --enable-spdk
INFO[2025-12-15T13:18:01+08:00] Initializing preflight installer             
INFO[2025-12-15T13:18:01+08:00] Cleaning up preflight installer              
INFO[2025-12-15T13:18:03+08:00] Running preflight installer                  
INFO[2025-12-15T13:18:03+08:00] Installing dependencies with package manager 
ERRO[2025-12-15T13:18:33+08:00] Failed to run preflight installer: failed to install dependencies with package manager: failed DaemonSet condition check: pod container is in crash loop. View the logs using "kubectl -n longhorn-system logs longhorn-preflight-installer-5h9hm -c init-longhornctl" 

$ kubectl get pods -n longhorn-system
NAME                                 READY   STATUS                  RESTARTS      AGE
longhorn-preflight-installer-5h9hm   0/1     Init:CrashLoopBackOff   6 (66s ago)   6m42s
longhorn-preflight-installer-b2zfh   0/1     Init:CrashLoopBackOff   6 (52s ago)   6m42s
longhorn-preflight-installer-fz2lz   0/1     Init:CrashLoopBackOff   6 (58s ago)   6m42s

$ kubectl logs longhorn-preflight-installer-b2zfh -n longhorn-system -c init-longhornctl
time="2025-12-15T05:18:47Z" level=info msg="Updating package list"
time="2025-12-15T05:18:47Z" level=error msg="Failed to run preflight installer: failed to update package list: failed to execute: nsenter [--mount=/host/proc/3809/ns/mnt --net=/host/proc/3809/ns/net zypper update -y], output , stderr This is a transactional-server, please use transactional-update to update or modify the system.\n: exit status 5"

cc @derekbit </comment_new>
<comment_new>@derekbit
@yangchiu
For sles-micro, please check longhorn/longhorn#9256 (comment) instead and it is not in the scope of the ticket.

Please test the feature using OpenEuler or other OSs.</comment_new>
<comment_new>@yangchiu

@yangchiu For sles-micro, please check #9256 (comment) instead and it is not in the scope of the ticket.

Please test the feature using OpenEuler or other OSs.

Sure! I won't verify this ticket on sle-micro anymore.</comment_new>
<comment_new>@yangchiu
Tested on master-head (longhorn/cli 63745e4). longhornctl fails to run on openEuler 24.03:

# cat /etc/os-release 
NAME="openEuler"
VERSION="24.03 (LTS)"
ID="openEuler"
VERSION_ID="24.03"
PRETTY_NAME="openEuler 24.03 (LTS)"
ANSI_COLOR="0;31"

# ./longhornctl insta...

</details>


> **Custom agent used: longhorn-important-notes-agent**
> Agent for automating Longhorn documentation updates and important notes.



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- Fixes longhorn/longhorn#12153

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