This one time, at band camp, Tony Green wrote:
>I'm wading back into cfengine after a bit of a break and I'm running into the same
>problems, hopefully one of the cfengine advocates out there will be able point me in
>the right direction.
>
>A typical example is:
>
>I'm editing /etc/system on solaris, I want to ensure that this line is
>set :
>set shmsys:shminfo_shmmax=4294967296
>
>I can use the 'AppendIfNoSuchLine' command and that'll work fine the
>first time around. My issue is, what happens the next time I want to
>change that line?
>
>I could switch to the 'ReplaceLineWith' command, but that won't add the
>line if it doesn't exist.
>
>Is there a sensible way around this? I'm guessing I might be missing
>something but a couple of dives through the refernce manual turned up
>naught.
The problem boils down to the difference between a configuration file
and ordinary text files.
There is currently no way in cfengine to say "this file /etc/system is a
configuration file, it has key/value pairs, and to set one you use the
template 'set x=y'". I say currently because it's been my plan for the
last year to add this functionality.
But it's not all lost... I currently have a template of editfiles
commands to do almost the same thing:
Given a file X, a variable Y, and a value Z, I do something like this:
control:
X_Y = ( Z )
editfiles:
{ X
BeginGroupIfNoLineMatching '^Y =.*'
Append 'Y ='
EndGroup
ResetSearch 1
LocateLineMatching '^Y =.*'
ReplaceLineWith 'Y = $(X_X)'
}
which roughly translates into 'if there's no Y in the config file, edit
it. now there's a Y, so find it, and replace it with the correct
line'.
So you want something like:
{ /etc/system
BeginGroupIfNoLineMatching '^set shmsys:shminfo_shmmax=.*'
Append 'set shmsys:shminfo_shmmax='
EndGroup
ResetSearch 1
LocateLineMatching '^set shmsys:shminfo_shmmax=.*'
ReplaceLineWith 'set shmsys:shminfo_shmmax=4294967296'
}
I also wrote an article on it for work:
http://shipyard.anchor.com.au/shipyard/articles/sysadmin/cfengine-configfiles.py
To make things easier (and remove the chance for error) I've got some M4
macros that autogenerate these templates. At the above url I plan to
write more about our cfengine installation over the next few weeks.
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