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Re: [ANNOUNCEMENT] TEST RELEASE: Cygwin 1.7.33-0.1

On 10/28/2014 08:20 AM, Corinna Vinschen wrote:
>>> Now that you mention it... yes, a service dependency might be helpful.
>>> Unfortunately it's tricky to automate this.  Is it possible to add
>>> service deps after having installed a service?
>> According to
>> it is possible to add a dependency to an already existing service.  I
>> agree it would be hard to automate in the install scripts, as one
>> would have to either ask the user about their intent to run other
>> services or rely that they configured cygserver first and then check
>> to see if it has been already configured to determine if a dependency
>> should be created.  I would think that some instructions in the docs
>> near the statement mentioned above would be more than sufficient,
>> since this is a "fine tuning" sort of thing.
> Agreed.  Do you have some idea how to phrase this?  I'd be grateful
> for a nice two or three paragraphs discussing this.

On Linux, systemd has a notion of soft dependencies, where any service
can do a one-sided advertisement that "if this other service is also
installed, then here is the order that must be observed between bringing
the two services up; but there is no requirement that the other service
be installed".  Note in particular that both 'before' and 'after' soft
dependencies can be specified.  I wonder if cygserver could be taught to
do something similar - but it would probably be a lot of work.
cygserver would have to maintain some sort of database of requested
dependencies, and then when installing a service, it would check both if
the current service has any soft dependency on other installed cygserver
services, as well as whether any other installed cygserver service has a
soft dependency on the service being installed, and in either case, add
a Windows hard dependency on the correct service.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library

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