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Kai Walter
Kai Walter

Posted on • Updated on

Manage SSH config entries with a PowerShell module

I wanted to do this for months now. This afternoon, to procrastinate a slightly more complex task on my vacation bucket list, I finally took the time and created this PowerShell module.

It is quite simple but caters my need to manage clean configuration files.

!!!DISCLAIMER!!! no warranty - please test the behavior of this script for thoroughly your environment and make regular backups

How to use the module

Once the module is imported

Import-Module .\ManageSshConfig.psm1
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it allows

a - to read the list of configured hosts into a HashTable

$hostList = Get-ConfigHostList
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b - to add a new entry to this list of hosts

$hostList = Add-ConfigHostInList -HostList $hostList -HostName "dummy" -HostValues @{
    identityfile = "~/.ssh/myprivatekey"
    hostname     = "dummy.somecloud.com"
    user         = "johndoe"
}
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c - to update an existing entry in this list of hosts

$hostList = Update-ConfigHostInList -HostList $hostList -HostName "dummy" -HostValues @{
    identityfile = "~/.ssh/myprivatekey"
    hostname     = "dummy.somecloud.com"
    user         = "johndoe"
}
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d - to remove an existing entry from this list of hosts

$hostList = Remove-ConfigHostFromList -HostList $hostList -HostName "dummy"
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e - and then write this list back to disk

Set-ConfigHostList $hostList
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Features

Line breaks

The script should be able to identify the line breaks used in the config file. This could be CR/LF on Windows and definitely are LF on Linux, macOS & alike.

If this sounds unfamiliar to you, check out Scott Hanselman's nice explanation on this topic.

on my Windows machine I forced Visual Studio Code to always safe it with LF line endings - just to be safe when copying this file back and forth between various OS platforms

Keywords

Keywords like IdentityFile or HostName are harmonized when

  • reading from config file into HashTable
  • adding or updating entries

according to notation usually seen in documentation like.

JSON

Once list of hosts is loaded, it can also by converted to JSON:

$hostList = Get-ConfigHostList
$hostList | ConvertTo-Json
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{
  "dummy": {
    "User": "johndoe",
    "HostName": "dummy.somecloud.com",
    "IdentityFile": "~/.ssh/myprivatekey"
  }
}
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This even allows to export SSH config to a JSON file, manage it in that format and then import it back:

$hostList = Get-ConfigHostList
$hostList | ConvertTo-Json -AsHashtable | Set-Content "ssh-config.json"
... do your magic here ...
$hostList = Get-Content "ssh-config.json" | ConvertFrom-Json -AsHashtable
Set-ConfigHostList $hostList
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Top comments (1)

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Kai Walter Author

added JSON samples