Patching in ABS
- There have been quite a few questions about creating and/or applying patches to packages when using ABS. This document outlines the steps and options required to do these tasks. http://www.kegel.com/academy/opensource.html also has some useful information on patching files.
If you are attempting to use a patch that you got from elsewhere (ie: you downloaded a patch to the Linux kernel), you can skip to the next section. However, if you need to edit source code, make files, configuration files, etc, you will need to be able to create a patch.
Note: If you need only to change one or two lines in a file (ie: a Makefile), you may be better off investigating the properties of
Creating a patch for a package involves creating two copies of the package, editing the new copy, and creating a unified diff between the two files. When creating an Arch Linux package, this can be done as follows:
- Add the download source of the file to the source array of the
PKGBUILDyou are creating. Of course, if you are altering an existing PKGBUILD, this step is taken care of.
- Create a dummy (empty, or containing a single
echocommand is good) build() function. If you are altering an existing
PKGBUILD, you should comment out most of the lines of the build function, as you're likely going to be running
makepkgseveral times, and you won't want to spend a lot of time waiting for a broken package to build.
makepkgThis will download the source files you need to edit into the
- Change to the
srcdirectory. In standard cases, there will be a directory containing a bunch of files that were unzipped or untarred from a downloaded archive there (Sometimes it's a single file, but diffs work on multiple files too!) You should make two copies of these directories. One is a pristine copy that makepkg won't be allowed to manipulate, and one will be the new copy that you will create a patch from. You can name the two copies
package.newor something similar.
- Change into the
package.newdirectory. Edit whichever files need to be edited. The changes needed depend on what the patch has to do; it might correct a Makefile paths, it may have to correct source errors (for example, to agree with
gcc 3.4), and so on. You can also edit files in subfolders of the
package.newdirectory, of course. Do not issue any commands that will inadvertantly create a bunch of files in the
package.newdirectory; ie: do not try to compile the program to make sure your changes work. The problem is that all the new files will show up in the patch, and you don't want that. Instead, apply the patch to another copy of the directory (not the pristine directory), either manually with the
patchcommand, or in the
PKGBUILD(described below) and test the changes from there.
- Change back to the
diff -aur package.pristine package.newThis will output all the changes you made in unified diff format. You can scan these to make sure the patch is good.
diff -aur package.pristine package.new > package.patchto capture all the changes in a file named
package.patch. This is the file that will be used by patch. You may now apply the changes to a copy of the original directory and make sure they are working properly. You should also check to ensure that the patch does not contain any extraneous details. For example, you don't want the patch to convert all tabs in the files you edited to spaces because your text editor did that behind your back. You can edit the patch either using a text editor, or to be safer (and not accidentally introduce errors into the diff file), edit the original files and create the patch afresh.
This section outlines how to apply patches you created or downloaded from the Internet from within a
build() function. Follow these steps:
- Add an entry to the
sourcearray of the
PKGBUILDfor the patch file. If the file is available online, you can provide the full URL and it will automatically be downloaded and placed in the
srcdirectory. If it is a patch you created yourself, or is otherwise not available, you should place the file in the same directory as the
PKGBUILDfile, and just add the name of the file to the source array so that it is copied into the
srcdirectory. If you redistribute the
PKGBUILD, you should, of course, include the patch with the
- Create the
build()function in the
PKGBUILD. In most cases you will want to apply the patch first thing in the function, but you will know best where the patch lines need to be applied.
- The first step in is to change into the directory that needs to be patched (in the
build()function, not on your terminal! You want to automate the process of applying the patch). You can do this with something like
cd $startdir/src/$pkgname-$pkgveror something similar.
$pkgname-$pkgveris often the name of a directory created by untarring a downloaded source file, but not in all cases.
- Now you simply need to apply the patch from within this directory. This is very simply done by adding
patch -p1 -i ../pkgname.patchto your
pkgname.patchto the name of the file containing the diff (the file that was automatically copied into your
srcdirectory because it was in the
sourcearray of the
makepkg(from the terminal now). If all goes well, the patch will be automatically applied, and your new package will contain whatever changes were included in the patch. If not, you may have to experiment with the
-poption of patch. read
man patchfor more information.
Basically it works as follows. If the diff file was created to apply patches to files in
myversion/, the diff files will be applied to
myversion/file. You are running it from within the
yourversion/ directory (because you cd'd into that directory in the
PKGBUILD), so when patch applies the file, you want it to apply it to the file
file, taking off the
-p1 does this, by removing one directory from the path. However, if the developer patched in
myfiles/myversion, you need to remove two directories, so you use
If you don't apply a -p option, it will take off all directory structure. This is ok if all the files are in the base directory, but if the patch was created on
myversion/ and one of the edited files was
myversion/src/file, and you run the patch without a
-p option from within
yourversion, it will try to patch a file named
Most developers create patches from the parent directory of the directory that is being patched, so
-p1 will usually be right.