On Wed 17 Feb 2021 at 07:49:57 (+0800), Kevin Shell wrote: > On Wed, Feb 17, 2021 at 07:47:51AM +0800, Kevin Shell wrote: > > On Wed, Feb 17, 2021 at 07:39:15AM +0800, Kevin Shell wrote: > > > On Tue, Feb 16, 2021 at 04:38:06PM -0600, David Wright wrote: > > > > On Tue 16 Feb 2021 at 17:48:25 (+0800), Kevin Shell wrote: > > > > > > > [...] > > > > > Isn't Debian already has a /etc/alternatives/ mechanism? > > > > > > > > AIUI all the targets of /etc/alternatives are all installed at the > > > > same time, and can be simultaneously run without conflicting with > > > > each other. The links merely select which target is run (and > > > > documented) by invoking a name, like "www-browser" (→ lynx for me), > > > > "awk" (gawk) or "rename" (the Perl one). I might be running firefox, > > > > mawk and rename.ul (by their specific name) at the same time as the > > > > "default" versions. > > > > > > > I asked this question because on my laptop there's an alternatives system > > > that can keep several programs providing the same or similar functions > > > at the same time. > > > Debian also has an alternatives system but doesn't allowed to install > > > multiple MTAs. > > > > > > https://github.com/fedora-sysv/chkconfig/blob/master/alternatives.c > > > $ dnf info alternatives > > > Name : alternatives > > > Summary : A tool to maintain symbolic links determining default > > > commands > > > URL : https://github.com/fedora-sysv/chkconfig > > > License : GPLv2 > > > Description : alternatives creates, removes, maintains and displays > > > information about > > > : the symbolic links comprising the alternatives system. It > > > is possible > > > : for several programs fulfilling the same or similar > > > functions to be > > > : installed on a single system at the same time. > > > > > besides BSD systems also have a similar system call mailwrapper > called > > http://man.openbsd.org/mailwrapper.8
AIUI (and I'm not one to be playing these tricks), it doesn't seem to do more than using, say, . Debian's alternatives to create a dummy package that satisfies apt's dependencies, and . installing your favoured foreign replacement in, say, /opt. Again, I'll pass on looking for documentation on switching MTAs using mailwrapper. Cheers, David.
