Augeas

Augeas & XPath

References

• Puppet with Augeas (augtool to be install): http://projects.puppetlabs.com/projects/1/wiki/puppet_augeas#Adding+a+service+that+uses+both+TCP+and+UDP+to+/etc/services
• Augeas presentation: http://www.slideshare.net/PuppetLabs/configuration-with-augeas#btnNext
• Augeas add node: https://github.com/hercules-team/augeas/wiki/Adding-nodes-to-the-tree
• XPath (for augtool): http://www.w3schools.com/XPath/xpath_syntax.asp
• XPath (for augtool): https://github.com/hercules-team/augeas/wiki/Path-expressions

augtool

ATTENTION: this is not how Augeas is used in puppet, this is just to exercise with augtool that is normally not used...

 
[root@sapocvm2 ~]# augtool # the interactive augtool is ONLY installed on vm2 (other nodes use the lib and ruby binding for puppet)
augtool> print /files/etc/hosts/*
/files/etc/hosts/#comment = "127.0.0.1\tlocalhost localhost.localdomain"
/files/etc/hosts/1
/files/etc/hosts/1/ipaddr = "127.0.0.1"
/files/etc/hosts/1/canonical = "localhost"
/files/etc/hosts/2
/files/etc/hosts/2/ipaddr = "::1"
/files/etc/hosts/2/canonical = "localhost6"
/files/etc/hosts/2/alias = "localhost6.localdomain6"
/files/etc/hosts/3
/files/etc/hosts/3/ipaddr = "10.226.58.167"
/files/etc/hosts/3/canonical = "puppet"
/files/etc/hosts/3/alias[1] = "salt"
/files/etc/hosts/3/alias[2] = "sapocvm1"

augtool> print /files/etc/hosts/*/alias
/files/etc/hosts/2/alias = "localhost6.localdomain6"
/files/etc/hosts/3/alias[1] = "salt"
/files/etc/hosts/3/alias[2] = "sapocvm1"

Using XPath...

augtool> match /files/etc/hosts/*[canonical='localhost']
/files/etc/hosts/1 = (none)

augtool> match /files/etc/hosts/*/ipaddr[../canonical='localhost']
/files/etc/hosts/1/ipaddr = 127.0.0.1

The single dot . and double dots .. are short for self::* and parent::*.
2 examples to demo
augtool> match /files/etc/hosts/*/canonical[.=~regexp('local.*')]
/files/etc/hosts/1/canonical = localhost
/files/etc/hosts/2/canonical = localhost6
augtool> match /files/etc/hosts/*/canonical[self::*=~regexp('local.*')]
/files/etc/hosts/1/canonical = localhost
/files/etc/hosts/2/canonical = localhost6

The single dot . and double dots .. are short for self::* and parent::*.
2 examples to demo
augtool> match /files/etc/hosts/*/canonical[../alias=~regexp('sa.*')]
/files/etc/hosts/3/canonical = puppet
augtool> match /files/etc/hosts/*/canonical[parent::*/alias=~regexp('sa.*')]
/files/etc/hosts/3/canonical = puppet

augtool> match /files/etc/hosts/*/ipaddr[../alias=~regexp('sa.*') or ../canonical=~regexp('pup.*')]
/files/etc/hosts/3/ipaddr = 10.226.58.167

augtool> print /files/etc/hosts/*/alias[last()-1]
/files/etc/hosts/3/alias[1] = "salt"

augtool> print /files/etc/hosts/*[last()]/*
/files/etc/hosts/3/ipaddr = "10.226.58.167"
/files/etc/hosts/3/canonical = "puppet"
/files/etc/hosts/3/alias[1] = "salt"
/files/etc/hosts/3/alias[2] = "sapocvm1"