Generate uptime report

Script 2 min read Windows PowerShell 5.1 and PowerShell 7

Written and tested by Dhrub Bharali · Updated 02 October 2026

Query Win32_OperatingSystem on each computer and calculate uptime from LastBootUpTime. Check unreachable hosts before using the report.

The script

1PS> $Computers = "SRV01", "SRV02"

2PS> Get-CimInstance Win32_OperatingSystem -ComputerName $Computers | Select-Object CSName,@{ Name = "UptimeHours"; Expression = {(New-TimeSpan $_.LastBootUpTime (Get-Date)).TotalHours} }

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$Computers = "SRV01", "SRV02"
Get-CimInstance Win32_OperatingSystem -ComputerName $Computers | Select-Object CSName,@{ Name = "UptimeHours"; Expression = {(New-TimeSpan $_.LastBootUpTime (Get-Date)).TotalHours} }

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Show reference output

1 CSName UptimeHours

2 ------ -----------

3 SRV01 73.5

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Read the command and its supplied arguments. This example requires real PowerShell or its module; this diagram does not execute it.

$Computers = "SRV01", "SRV02"
Get-CimInstance Win32_OperatingSystem -ComputerName $Computers | Select-Object CSName,@{ Name = "UptimeHours"; Expression = {(New-TimeSpan $_.LastBootUpTime (Get-Date)).TotalHours} }

Stage 1$ComputersPositional values or no named parameters
Stage 2Select-ObjectPositional values or no named parameters

How it works

Query Win32_OperatingSystem on each computer and calculate uptime from LastBootUpTime. Check unreachable hosts before using the report. A calculated property named UptimeHours feeds LastBootUpTime and the current time into New-TimeSpan and reads TotalHours off the resulting span. CSName travels with each row so the output identifies its own source without a separate join.

Adapting it

Wrap the TotalHours expression in [math]::Round, or divide by 24 for a days column. Piping into Where-Object UptimeHours -gt 720 turns the report into a list of hosts overdue for a restart.

Requirements

WinRM reachable on every target plus rights to query CIM remotely.

If the result is unexpected

Some hosts return an uptime figure while others produce a connection error, and the whole command takes minutes to finish.

Passing -ComputerName opens a WS-Management connection per host, so any target with WinRM stopped or firewalled fails individually after burning the full timeout. Those failures are non-terminating, which is why partial output arrives mixed in with a stack of red text. A name that does not resolve fails the same way for an entirely different reason.

Filter the host list first with Test-NetConnection on port 5985 so unreachable targets never reach the query.
Create sessions up front with New-CimSession and inspect which ones failed, separating connectivity from query problems.
Add -OperationTimeoutSec to cap the wait per host rather than accepting the default.
Check whether the failing hosts resolve at all, since a stale DNS record produces an identical symptom.
Run against a small known-good subset first to confirm the syntax before blaming the environment.

Validate the result

Every host in the filtered list returns a CSName with an UptimeHours value, and no error records appear in the output.

Keep the check reliable

Build the target list from something authoritative rather than a static array, and pre-test reachability so a report does not spend its runtime waiting on decommissioned hosts.