轉載 http://meinit.nl/rpm-spec-prepostpreunpostun-argument-values

RPM has 4 parts where (shell) scripts can be used:

• %pre - Executed before installation.
• %preun - Executed before un-installation.
• %post - Executed after installation.
• %postun - Executed after un-installation.

In all these parts or sections the variable "$1" can be checked to see what's being done:

• Initial installation
• Upgrade
• Un-installation

This table show the values of "$1" per section related to the action.

?	%pre	%preun	%post	%postun
Initial installation	1	not applicable	1	not applicable
Upgrade	2	1	2	1
Un-installation	not applicable	0	not applicable	0

This can be used for example when registering new services:

%post case "$1" in1)# This is an initial install.chkconfig --add newservice;;2)# This is an upgrade.# First delete the registered service.chkconfig --del newservice# Then add the registered service. In case run levels changed in the init script, the service will be correctly re-added.chkconfig --add newservice;; esac%preun case "$1" in0)# This is an un-installation.service newservice stopchkconfig --del newservice;;1)# This is an upgrade.# Do nothing.:;; esac

Good to know; this is the order for certain RPM actions:

install	upgrade	un-install
%pre ($1=1)	%pre ($1=2)	%preun ($1=0)
copy files	copy files	remove files
%post ($1=1)	%post ($1=2)	%postun ($1=0)
?	%preun ($1=1) from?old?RPM.	?
?	delete files only found in old package	?
?	%postun ($1=1) from?old?RPM.	?

So when upgrading the exemplary package "software" from version 1 to version 2, this is the script (%post and %postun) order:

Run %pre from "software-2".

Place files from "software-2".

Run %post from "software-2".

Run %preun from "software-1".

Delete files unique to "software-1".

Run %postun from "software-1".

This means there are cases where "software-1" has incorrect scripts, and there is no way to upgrade. In that case the RPM can be uninstalled, which might execute different commands because $1 equals 0 (un-install) instead of 1 (upgrade).
When the RPM uninstall scripts fail, the only way to fix things is to manually execute the intended commands... RPM is not perfect, but it's pretty well thought through!

轉載于:https://www.cnblogs.com/xingmuxin/p/8990255.html

總結

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