[augeas-devel] Having a bit of trouble with the ssh lense

[Dominic Cleal]

Hi Pat,

On 11/11/11 18:24, Pat Riehecky wrote:
> Lets say my ideal /etc/ssh/ssh_config looks like this
> 
> 
> Host A
>         GSSAPIAuthentication yes
> Host B
>         GSSAPIAuthentication yes
>         ForwardX11 yes
> Host *
>         ForwardX11Trusted yes
> 
> 
> 
> And my current one looks like:
> 
> 
> Host A
>         GSSAPIAuthentication yes
> Host *
>         ForwardX11Trusted yes
> 
> 
> 
> I haven't been able to find a good way to locate 'Host *' and put 'Host
> B' above it.
> $ augtool ls /files/etc/ssh/ssh_config/
> Host[1]/ = A
> Host[2]/ = *
> 
> I've tried:
> 
> ls /files/etc/ssh/ssh_config[ Host = '*' ]
> ls /files/etc/ssh/*[ Host = '*' ]

Nearly:

augtool> match /files/etc/ssh/ssh_config/Host[ . = '*' ]
/files/etc/ssh/ssh_config/Host[2] = *

The expression Host[ . = '*' ] is looking for Host nodes and the "."
refers to the value of the node (or self::*).  The reason the first
command didn't work as expected is because it looks for an ssh_config
node where a subnode Host is "*".  You actually want to match the Host
node itself, so that has to be in the path on the left.

This wiki page has some examples that can be useful:

http://augeas.net/page/Path_expressions

> But, while strange, my main problem is I have no idea how to even add a
> new host definition.
> 
> augtool ins B before /files/etc/ssh/ssh_config/Host[2]
> 
> Just doesn't work.

You're close... instead, you need "ins Host .." as you add the node with
the label "Host" and then once it's there you can set the value of the
node to "B".  Check "help ins" in augtool and it'll refer to the label
as opposed to the value.

So in full:

augtool> ls /files/etc/ssh/ssh_config/
Host[1]/ = A
Host[2]/ = *
augtool> ins Host before /files/etc/ssh/ssh_config/Host[ . = '*' ]
augtool> set /files/etc/ssh/ssh_config/Host[ . = '' ] B
augtool> ls /files/etc/ssh/ssh_config/
Host[1]/ = A
Host[2] = B
Host[3]/ = *
augtool> set /files/etc/ssh/ssh_config/Host[ . = 'B'
]/GSSAPIAuthentication yes
augtool> set /files/etc/ssh/ssh_config/Host[ . = 'B' ]/ForwardX11 yes
augtool> print /files/etc/ssh/ssh_config/
/files/etc/ssh/ssh_config
/files/etc/ssh/ssh_config/Host[1] = "A"
/files/etc/ssh/ssh_config/Host[1]/GSSAPIAuthentication = "yes"
/files/etc/ssh/ssh_config/Host[2] = "B"
/files/etc/ssh/ssh_config/Host[2]/GSSAPIAuthentication = "yes"
/files/etc/ssh/ssh_config/Host[2]/ForwardX11 = "yes"
/files/etc/ssh/ssh_config/Host[3] = "*"
/files/etc/ssh/ssh_config/Host[3]/ForwardX11Trusted = "yes"
augtool> save
Saved 1 file(s)

Hope that helps.

Cheers,

-- 
Dominic Cleal
Red Hat Consulting
m: +44 (0)7817 878113