Weird behavior when --add-slave and --keep-foreign used together for active alternative
#102
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Yep, this is a bug. This combination should work.
Well, the correct definition is: --keep-foreign prevents changing a symlink if it is not a symlink created by alternatives. |
lnykryn
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Normally alternatives will only refuse to create a link to /etc/alternatives/* if the file already exists and is not a symlink. But alternatives never checked if existing symlink goes to /etc/alternatives/. This is a weird behavior, but we did not want to change the default behavior so we added --keep-foreign option that is more strict and checks that the target if the symlink is in /etc/alternatives/. But we missed the corner-case where there is no file at all and incorrectly reported on error. Fixes fedora-sysv#102
lnykryn
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Apr 9, 2023
Normally alternatives will only refuse to create a link to /etc/alternatives/* if the file already exists and is not a symlink. But alternatives never checked if existing symlink goes to /etc/alternatives/. This is a weird behavior, but we did not want to change the default behavior so we added --keep-foreign option that is more strict and checks that the target if the symlink is in /etc/alternatives/. But we missed the corner-case where there is no file at all and incorrectly reported on error. Fixes fedora-sysv#102
lnykryn
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Apr 13, 2023
Normally alternatives will only refuse to create a link to /etc/alternatives/* if the file already exists and is not a symlink. But alternatives never checked if existing symlink goes to /etc/alternatives/. This is a weird behavior, but we did not want to change the default behavior so we added --keep-foreign option that is more strict and checks that the target if the symlink is in /etc/alternatives/. But we missed the corner-case where there is no file at all and incorrectly reported on error. Fixes fedora-sysv#102
jamacku
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Apr 13, 2023
Normally alternatives will only refuse to create a link to /etc/alternatives/* if the file already exists and is not a symlink. But alternatives never checked if existing symlink goes to /etc/alternatives/. This is a weird behavior, but we did not want to change the default behavior so we added --keep-foreign option that is more strict and checks that the target if the symlink is in /etc/alternatives/. But we missed the corner-case where there is no file at all and incorrectly reported on error. Fixes #102
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Thank you for the fix! |
jamacku
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May 15, 2023
Normally alternatives will only refuse to create a link to /etc/alternatives/* if the file already exists and is not a symlink. But alternatives never checked if existing symlink goes to /etc/alternatives/. This is a weird behavior, but we did not want to change the default behavior so we added --keep-foreign option that is more strict and checks that the target if the symlink is in /etc/alternatives/. But we missed the corner-case where there is no file at all and incorrectly reported on error. Fixes fedora-sysv#102 (cherry picked from commit bd9b6cc)
jamacku
pushed a commit
that referenced
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May 15, 2023
Normally alternatives will only refuse to create a link to /etc/alternatives/* if the file already exists and is not a symlink. But alternatives never checked if existing symlink goes to /etc/alternatives/. This is a weird behavior, but we did not want to change the default behavior so we added --keep-foreign option that is more strict and checks that the target if the symlink is in /etc/alternatives/. But we missed the corner-case where there is no file at all and incorrectly reported on error. Fixes #102 (cherry picked from commit bd9b6cc)
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We have a problem in python3.11-wheel package which we can probably solve by ourselves but I think the strange behavior of alternatives I discovered is still worth reporting.
When talking about packages, I mean the ones available in RHEL 8 and I'm using 1minutetip for testing. The most important ones are chkconfig-1.19.1-1.el8.x86_64 and python3.11-wheel-0.38.4-3.el8.noarch.
To reproduce the problem on RHEL 8:
dnf install python36 python3.11(Python 3.6 is needed later.)alternatives --set python3 /usr/bin/python3.11dnf install python3.11-wheelThe installation of python3.11-wheel calls this command in its
%postscriptlet:alternatives --keep-foreign --add-slave python3 /usr/bin/python3.11 /usr/bin/wheel-3 wheel-3 /usr/bin/wheel-3.11The command produces the following error:
But, if you set the alternative for python3 to python36 which means that the installation of python3.11-wheel will add the slave into an inactive alternative, it works fine and no error is shown. So these steps are fine:
dnf install python36 python3.11alternatives --set python3 /usr/bin/python3.6dnf install python3.11-wheelIf I understand it correctly
--keep-foreignshould prevent the--add-slavefrom removing/changing a symlink, if it already exists. If that's true, having--add-slavetogether with--keep-foreignmakes perfect sense. The problem is that the error message is not true:/usr/bin/wheel-3does not exist in this case. Alternatives should create that file if you install python3.11-wheel when python3.11 is the active alternative for python3.To sum this up:
/usr/bin/wheel-3and shows the error mentioned above./usr/bin/wheel-3is there and works as expected:/usr/bin/wheel-3 -> /etc/alternatives/wheel-3 -> /usr/bin/wheel-3.11.Bug report with some more context: https://bugzilla.redhat.com/show_bug.cgi?id=2181479
Does it make sense to use
--keep-foreignwith--add-slave? If so, could we fix the problem? And if not, could we improve the error message to make it clear that this is not supported?The text was updated successfully, but these errors were encountered: