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Windows Check If Port is Listening

March 3, 2022 by Ulysses

Here’s how to check if port is listening on a Windows Server.

Log in to the destination server.

netstat -ano | find "443" | find "LISTEN"
tasklist /fi "PID eq "443"

netstat -ano | find "443" | find "LISTEN" tasklist /fi "PID eq "443"

Filed Under: Misc Tagged With: check, listening, netstat, port, tasklist, windows

Run Telnet on Git Bash

October 20, 2021 by Ulysses

Although telnet is not used regularly since insecure, it’s a handy tool for testing ports.

For example, to check if a port 80 is open, you run this command.

$ telnet servername 80

$ telnet servername 80

Git Bash does not come with telnet, but you can use the Windows version by using winpty.

$ winpty telnet servername 457
Connecting To servername...Could not open connection to the host, on port 457: Connect failed

$ winpty telnet servername 457 Connecting To servername...Could not open connection to the host, on port 457: Connect failed

If port is open, you get an empty reply, just like in Windows.

Filed Under: Linux Tagged With: check, git bash, ports, telnet, windows

Check Open Ports Remotely

August 17, 2021 by Ulysses

Here are a few tools to check if ports are open from a remote host.

nc -zvw10 192.168.0.1 22
nmap 192.168.0.1 -p 22
telnet 192.168.0.1 22

nc -zvw10 192.168.0.1 22 nmap 192.168.0.1 -p 22 telnet 192.168.0.1 22

You may have to install netcat and nmap if missing in your distro.

yum install nc
yum install nmap

yum install nc yum install nmap

Filed Under: Linux Tagged With: check, nc, nmap, open, ports, remote, telnet

Bash Variable Empty

August 6, 2021 by Ulysses

Here’s how to check in Bash if a variable is empty or unset.

if [ -z "${VAR}" ]; 
then
  echo 'do something'
else
  echo 'do another'
fi

if [ -z "${VAR}" ]; then echo 'do something' else echo 'do another' fi

One liner

if [ -z "${VAR}" ]; then echo 'do something'; else echo 'do another'; fi

if [ -z "${VAR}" ]; then echo 'do something'; else echo 'do another'; fi

The inverse

if [ ! -z "${VAR}" ]; 
then
  echo 'do something'
else
  echo 'do another'
fi

if [ ! -z "${VAR}" ]; then echo 'do something' else echo 'do another' fi

if [ ! -z "${VAR}" ]; then echo 'do something'; else echo 'do another'; fi

if [ ! -z "${VAR}" ]; then echo 'do something'; else echo 'do another'; fi

Filed Under: Linux Tagged With: bash, check, empty, unset, variable

Check Reboot After Updates

July 16, 2021 by Ulysses

Here’s the command to check if the system needs a reboot after running yum update.

Must be root or run it sudo.

$ needs-restarting -r ; echo $?
Core libraries or services have been updated:
  openssl-libs -> 1:1.0.2k-21.el7_9
  kernel -> 3.10.0-1160.31.1.el7
  dbus -> 1:1.10.24-15.el7
  linux-firmware -> 20200421-80.git78c0348.el7_9
  glibc -> 2.17-324.el7_9
  systemd -> 219-78.el7_9.3
 
Reboot is required to ensure that your system benefits from these updates.
 
More information:
https://access.redhat.com/solutions/27943
1

$ needs-restarting -r ; echo $? Core libraries or services have been updated: openssl-libs -> 1:1.0.2k-21.el7_9 kernel -> 3.10.0-1160.31.1.el7 dbus -> 1:1.10.24-15.el7 linux-firmware -> 20200421-80.git78c0348.el7_9 glibc -> 2.17-324.el7_9 systemd -> 219-78.el7_9.3 Reboot is required to ensure that your system benefits from these updates. More information: https://access.redhat.com/solutions/27943 1

In this instance, it requires a reboot due to a new kernel.

Filed Under: Linux Tagged With: centos, check, reboot, redhat, update

Yum Check Update

July 9, 2021 by Ulysses

To check which packages are available for an update.

yum check-update

yum check-update

Filed Under: Linux Tagged With: check, packages, update, yum

Check If Domain Joined

October 28, 2020 by Ulysses

Here’s the command to check if instance is domain joined.

realm discover domain.com

realm discover domain.com

To check if AD user is working.

id user@ad.example.com

id user@ad.example.com

To check if AD group is working.

getent group ad-group

getent group ad-group

Filed Under: Linux Tagged With: check, domain, join, sssd, user

GCE Agent Powershell

May 11, 2020 by Ulysses

This is a Powershell script to restart a service if it’s down.

$ServiceName = 'GCEAgent'
$arrService = Get-Service -Name $ServiceName
 
if ($arrService.Status -ne 'Running')
{
 
    Start-Service $ServiceName
    write-host $arrService.status
    write-host 'Service starting'
    Start-Sleep -seconds 60
    $arrService.Refresh()
    if ($arrService.Status -eq 'Running')
    {
        Write-Host 'GCE Agent Service is now Running'
    }
 
}
else
{
    Write-Host 'GCE Agent Service is Running'
}

$ServiceName = 'GCEAgent' $arrService = Get-Service -Name $ServiceName if ($arrService.Status -ne 'Running') { Start-Service $ServiceName write-host $arrService.status write-host 'Service starting' Start-Sleep -seconds 60 $arrService.Refresh() if ($arrService.Status -eq 'Running') { Write-Host 'GCE Agent Service is now Running' } } else { Write-Host 'GCE Agent Service is Running' }

Filed Under: Cloud, Windows Tagged With: check, powershell, restart, service

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