Chapter 7. Declaring relationships between packages

50

postrm

script will be run with a special argument to allow the package to do any final cleanup

required. See `Summary of ways maintainer scripts are called' on page

40

.

1

For this usage of

Replaces

, virtual packages (see `Virtual packages  

Provides

' on page

48

)

are not considered when looking at a

Replaces

field   the packages declared as being replaced

must be mentioned by their real names.

Furthermore, this usage of

Replaces

only takes effect when both packages are at least par 

tially on the system at once, so that it can only happen if they do not conflict or if the conflict

has been overridden.

7.5.2 Replacing whole packages, forcing their removal

Secondly,

Replaces

allows the packaging system to resolve which package should be re 

moved when there is a conflict   see `Conflicting binary packages  

Conflicts

' on page

48

.

This usage only takes effect when the two packages do conflict, so that the two usages of this

field do not interfere with each other.

In this situation, the package declared as being replaced can be a virtual package, so for exam 

ple, all mail transport agents (MTAs) would have the following fields in their control files:

Provides: mail transport agent

Conflicts: mail transport agent

Replaces: mail transport agent

ensuring that only one MTA can be installed at any one time.

7.6 Relationships

between

source

and

binary

pack 

ages

Build Depends

,

Build Depends Indep

,

Build Conflicts

,

Build Conflicts Indep

Source packages that require certain binary packages to be installed or absent at the time of

building the package can declare relationships to those binary packages.

This is done using the

Build Depends

,

Build Depends Indep

,

Build Conflicts

and

Build Conflicts Indep

control file fields.

Build dependencies on  build essential  binary packages can be omitted. Please see `Package

relationships' on page

19

for more information.

The dependencies and conflicts they define must be satisfied (as defined earlier for binary

packages) in order to invoke the targets in

debian/rules

, as follows:

2

1

Replaces is a one way relationship   you have to install the replacing package after the replaced package.

2

If you make  build arch  or  binary arch , you need Build Depends. If you make  build indep  or  binary 

indep , you need Build Depends and Build Depends Indep. If you make  build  or  binary , you need both.

There is no Build Depends Arch; the autobuilders will only need the Build Depends if they know how to build