On 04/10/2011 17:28, no-re...@cfengine.com wrote: > Forum: CFEngine Help > Subject: Re: "expand_scalars" in "copy_from"? > Author: davidlee > Link to topic: https://cfengine.com/forum/read.php?3,23643,23671#msg-23671 > > Neil, your point about locally caching the template file (separating copy and > edit stages) is worth consideration. > > But in the other direction there is an as yet unmentioned point in favour of > a single "copy-then-edit". With "copy_from", sites can make extensive use of > "preserve" to maintain the permissions of the master file onto the copy on > the clients. When there is a set of several files, needing a variety of > different permissions, using "preserve" is both very clean and very clear. > > Sadly, forcing apart the copy and the edit phases of this suggested > "copy-and-edit" into two separate stages makes that more awkward. Yes, it can > be achieved by specifying the mode as an explicit number in the cfengine > promises. But for a set of files, all that has to be spelt out explicitly by > a mode clause per file; one is, alas, unable to use that clean, clear > "preserve" clause. > > The existing mechanism denies this possibility. It would be very nice if > this were available to use. > The problem of copy-and-edit is that the agent will have to copy the remote file at each execution, and then expand the scalar to compare with the content of the file; it is not possible to keep a track of what was the file before the editing ... I means that each time, the file would need to be sent over the network (if the server is unreachable, it is a problem, if the file is big, it is a problem), and detect modification on the template file would be more complex
On the other hand, first copying the template on a local location then editing a file based on this template is less resource-eater : - the template on the remote and the local are the same, it's easy to check for difference. - if the server is down or unreachable, it would still work - it's easy to expand the scalar on a local file to check if the content is the same than the file to be edited You rule out most of the issues, and you will know if : - the template change (reparation of the first promise) - the file has been tampered with (reparation of the second, but not the first one) Regards Nicolas _______________________________________________ Help-cfengine mailing list Help-cfengine@cfengine.org https://cfengine.org/mailman/listinfo/help-cfengine
