Comparing Installed Packages on Photon OS Using PowerShell and SSH

When debugging inconsistencies between Photon OS systems, say one is failing and another is stable, it’s useful to compare their installed package versions. In one recent case, I needed a quick way to do just that from my admin workstation. Here’s how I solved it using PowerShell and the Posh-SSH module.

In this test case, both hosts have a user account with the same name/password, so only one credential was created.

# Prompt for SSH credentials
$creds = Get-Credential

# Connect to Host 1 and get package list as JSON
$host1        = '192.168.10.135'
$host1session = New-SSHSession -ComputerName $host1 -Credential $creds -AcceptKey
$host1json    = (Invoke-SSHCommand -Command 'tdnf list installed -json' -SessionId $host1session.SessionId).Output | ConvertFrom-Json

# Connect to Host 2 and get package list as JSON
$host2        = '192.168.127.174'
$host2session = New-SSHSession -ComputerName $host2 -Credential $creds -AcceptKey
$host2json    = (Invoke-SSHCommand -Command 'tdnf list installed -json' -SessionId $host2session.SessionId).Output | ConvertFrom-Json

# Compare the resulting package lists
$compared = Compare-Object -ReferenceObject $host1json -DifferenceObject $host2json -Property Name, Evr

# Group the results by package name and build tabular results for side-by-side compare
foreach ($thisPackage in ($compared | Group-Object -Property Name)) {
  [pscustomobject][ordered]@{
    Name = $thisPackage.Name
    $host1 = ($thisPackage.Group | ?{$_.SideIndicator -eq '<='}).Evr
    $host2 = ($thisPackage.Group | ?{$_.SideIndicator -eq '=>'}).Evr
  }
}

The script gets a list of all installed packages from each host as JSON (using tdnf list installed -json), then converts the JSON output to a powershell object.
The two list of installed packages are then compared using Compare-Object.
Finally, we loop through each unique package and create a new object to compare the versions side by side.

I’ve included the first 10 rows of output below for reference.

Name                           192.168.10.135       192.168.127.174
----                           --------------       ---------------
cloud-init                     24.3.1-1.ph4         25.1-1.ph4
curl                           8.7.1-4.ph4          8.12.0-1.ph4
curl-libs                      8.7.1-4.ph4          8.12.0-1.ph4
elfutils                       0.181-7.ph4          0.181-8.ph4
elfutils-libelf                0.181-7.ph4          0.181-8.ph4
expat                          2.4.9-3.ph4          2.4.9-4.ph4
expat-libs                     2.4.9-3.ph4          2.4.9-4.ph4
gettext                        0.21-4.ph4           0.21-5.ph4
glib                           2.68.4-2.ph4         2.68.4-4.ph4
glibc                          2.32-19.ph4          2.32-20.ph4

Looking at this output, we can see which packages are different between our two hosts.

Conclusion

Comparing installed packages across Photon OS systems can be an invaluable troubleshooting and auditing tool – especially when dealing with configuration drift, unexpected behavior, or undocumented changes. By using PowerShell and the Posh-SSH module, you can quickly automate the comparison process without needing to log in to each system manually. Hopefully, this gives you a solid starting point for your own comparisons and debugging tasks.