Thanks for the additional info, Scott. On Wed, Mar 6, 2013 at 5:53 AM, Scott Moser <smo...@ubuntu.com> wrote: > On Tue, 5 Mar 2013, Bo Shi wrote: > >> Clint, Scott - sorry about the late reply. >> >> I did not explain myself particularly well. Here's another attempt. >> The CloudInit documentation section for "Multipart Input" states "[a] >> single format of user data might not be enough to accomplish what you >> want. For example, you may want to insert an upstart job and also run >> a user-data script." The example provided is: >> >> $ ls >> my-boothook.txt my-include.txt my-user-script.txt >> my-cloudconfig.txt my-upstart-job.txt >> >> $ write-mime-multipart --output=combined-userdata.txt \ >> my-boothook.txt:text/cloud-boothook \ >> my-include.txt:text/x-include-url \ >> my-upstart-job.txt:text/upstart-job \ >> my-user-script.txt:text/x-shellscript \ >> my-cloudconfig.txt >> >> Is the order of execution of the various parts deterministic? Can the >> order of execution be controlled in any manner, e.g. can I specify >> that "my-include.txt" depends on "my-user-script.txt" finishing? A >> rather contrived use-case is if my-cloudconfig.txt was used to create >> some users and my-include.txt performed some operation on those users' >> home directories. Another case is described in my original note. >> >> > To control order in which user-data is processed you should just need to >> > control the order in which it is created. >> >> Does this mean that the order in which the parts are specified in the >> invokation of "write-mime-multipart" above determines the order in >> which the parts gets executed? Is execution serial (my observations >> lean toward no here)? > > I guess I wasn't as clear as I could have been. > a.) the order output by 'write-mime-multipart' is the same as the order > of the command line arguments to it. If you find otherwise, please > let me know, thats a bug. > b.) the order consumed by cloud-init's user-data handling is in-order > that it appears in the user-data. In your example above, cloud-init > will process > * 'my-boothook.txt' > * then 'my-include.txt' > * anything included by my-include.txt (and recursively) > * my-upstart-job.txt > * my-user-script.txt > * my-cloudconfig.txt > c.) "process" above is unfortunately not so clear. Heres a guide: > * archive formats (mime or cloud-config-archive or include) are > exploded when found, and contents are processed at that point. > * cloud-config-data is merged into the existing cloud-config in the > order that it is seen. The merge routine for cloud-config is very > simplistic, and basically only supports overriding of fields. > Josh Harlow has a branch at [1] to fix a feature request in bug > 1023179 to make this more powerful. I'm really looking forward to > this. > [1] > https://code.launchpad.net/~harlowja/cloud-init/merge-types-differently/+merge/135310 > * boothook parts are executed immediately as they are processed. > (cloud-config 'bootcmd' are processed slightly later) > * upstart jobs are written to /etc/init immediately as they are > processed. And should the become ready for upstart usage > immediately. > * part-handlers are consumed immediately as they're seen, and then can > immediately act on subsequent parts. > * user-scripts are processed in the order they're seen, but the > * processing just means shoving them into a file in > /var/lib/cloud/instance/scripts (path from memory, so it could be > wrong). If the part has a filename, that filename is used. If not, > one is generated, and should increase. > > Then, later a 'runparts' equivalent is executed on that directory. > runparts executes in C locale sorted order. > > The files that cloud-init created will be invoked in the order that > they were written, but if you've provided filenames in the mime or > cloud-config-archive parts then you can change that ordering. > > Also, 'runcmd' parts (from cloud-confing) are dropped into a file > named 'runcmd' in that same directory. > > > That clear things up a bit? > Scott >
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