What is the function of 'Requires(pre)' in spec file?

[Florian Festi]

On 03/24/2016 09:58 AM, Zhang Freeman wrote:
> Hi List!
> 
> I post to ask for the differenced between 'Requires' and 'Requires(pre)'
> used in RPM spec file.
> 
> As RPM wiki[1] tells, dependency defined via 'Requires(pre)' should be
> fulfilled before installation and can be freely removed after
> installation, and 'Requires'  should be fulfilled after installation but
> before execution.
> 
> However, things won't stick to the script in real life. I find these two
> work in the same way.
> 
> Suppose I want to install package A, which depends on package B. RPM
> stops the process and warns me the dependency. After B is installed,
> installation of A turns to be succeed. Then I remove B, RPM erases both
> A and B! No matter it is "Requires(pre)" or "Requires".
> 
> Shouldn't A stay operational after I remove B if I use 'Requires(pre)' ?

Well, it should... not sure if the implementation really fully does it
that way. Also note, that there might be other dependencies for package
B that may prevent the erasure. Also note that dependency solver like
yum/dnf/zypper/... may have different idea of what packages to remove
than rpm itself (which actually doesn't select packages to remove a t
all, but just spits out error messages).

Another difficult to spot difference between Requires: and
Requires(pre): is package ordering during the installation. In case of
circular dependencies rpm give precedence to Requires(pre): dependencies
and rather breaks up normal Requires:

Florian

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