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uvsmtid
Asked: 2013-03-06 08:01:00 +0800 CST

Is there a way to list all configurable `alternatives` (symlinks for similar commands) on the system?

  • 772

The alternatives command (package chkconfig) on RHEL/Fedora manages symlinks which link a generic name to one of the alternative implementations. For example, mta group of symlinks can be provided by Sendmail and Postfix (to implement i.e. sendmail command):

alternatives --display mta

While I can --display a group of symlinks, I need to guess its name first (i.e. mta).

Can I simply list all possible configurable symlink groups (like mta) to pick from?

The reason is that I forget some group names occasionally.

linux

4 Answers

  1. On Debian (but not Fedora or RHEL), to see a list of all "master alternative names":

    update-alternatives --get-selections

    --get-selections list master alternative names and their status.

    And for each of those listed, you can run --list $ALTERNATIVE_NAME, e.g.

    update-alternatives --list editor

    --list name Display all targets of the link group.

    If you would like to see a list of all alternatives in their respective groups, you could run the following in fish shell:

    for alternative in (update-alternatives --get-selections)
    echo $alternative 
    update-alternatives --list (echo $alternative | cut -d" " -f1)
    echo
end | pager

    The (ba|z)?sh syntax should be something similar.

    To change the alternatives, run sudo update-alternatives --config $ALTERNATIVE_NAME

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  2. Best Answer

    The exact answer is (RHEL):

    ls /var/lib/alternatives

    Directory /etc/alternatives maintains flat long list of all symlinks mixing masters and slaves together. Slave symlinks cannot be used with alternatives --display [symlink] command.

    At the same time directory /var/lib/alternatives contains status information (including master-slave relationship) for each group in shortened list of file names all of which can be directly used with --display option. For example, /var/lib/alternatives/java:

    alternatives --display java
    • 20

  3. The simplest answer would be...

    ls /etc/alternatives
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  4. On Ubuntu 12.04 (may be some prior versions too, to be checked) and probably Debian too (to be checked):

    ls /var/lib/dpkg/alternatives

    List it just to get configurable alternative names, as entries in this directories are not links. By the way, there may be compressed file in this directory, so the names listed there, can't always be used as‑is. Ex. I have a /var/lib/dpkg/alternatives/psql.1.gz

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