Changes from Version 1 of DownGradeProblems

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Author:
skvidal (IP: 98.122.166.194)
Timestamp:
12/15/08 05:03:38 (9 years ago)
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  • DownGradeProblems

    v0 v1  
     1= Problems with performing downgrades = 
     2 
     3There are a number of problems with performing downgrades. I'll cover a few of them here: 
     4 
     5 * scriptlets are not reversible: 
     6   rpm scriptlets provide no way to reverse the process(es) they executed. For example a scriptlet (%pre, %preun, %post, %postun, etc) 
     7   may run echo "Foo foo foo" >> /etc/some/file. There's no way to undo that when you perform a downgrade. 
     8 
     9 * downgrading works provided the user data/user config is not modified by 
     10   an update in a one-way process.  
     11    Examples: mysql upgrade from  4->5 will convert a db, but going back the other way won't fly 
     12              upgrading a desktop application from one version to the next major version modifies config files in such a way but cannot 
     13              modify them back. 
     14 
     15 * There are certain processes which no one is ever going to do the work 
     16   to make them reversible: lvm1->lvm2, db transitions, udev migration, 
     17   ext3->ext4. 
     18 
     19The long and short is downgrades are possible right now. We don't expose them trivially b/c of all the trouble people get into when they perform them.  
     20 
     21If you only want to perform a simple downgrade from a minor version or release update of a package then your best bet is to use yumdownloader to fetch the older version and then using '''rpm -Uvh --replacepkgs --replacefiles --oldpackage file.rpm''' to downgrade it. 
     22