On 2014-02-23 13:17, David Chisnall wrote:
On 23 Feb 2014, at 18:11, Allan Jude <free...@allanjude.com> wrote:
sysrc solves this nicely, it is in base now, and is great for
programmatically adding, removing and changing lines in rc.conf style
files. It is also in ports for older versions of FreeBSD where it is
not
in base.
The problem is, there is no such thing as an rc.conf style file.
rc.conf is just a shell script. If you only edit it with sysrc, or
you are careful to preserve the structure, then it's fine. There is
absolutely nothing stopping you, however, from writing arbitrarily
complex shell scripts inside rc.conf. Sure, it's a terrible idea to
do so, but when has that ever stopped anyone?
An rc-replacement could enforce this by only accepting purely
declarative files for configuration, guaranteeing that if they were
syntactically valid they would also be machine editable, no matter
what the user does to them.
David
Just my $0.02:
I don't believe our current RC is broken. It's faster than most, it
supports an early-late divider, virtual targets (NETWORK, etc.),
dependencies, etc.
Rewriting scripts (units) in C has a non-trivial cost to customization
for end users. I have custom, packaged, RC scripts in /usr/local that
are pretty easy to add and maintain. Shell script logic can go there and
not in rc.conf proper. The rcorder program provides a pretty good idea
for when these can be run, and, as already pointed out, sysrc can be
used to add/remove/configure these on clusters of (automatically)
managed machines. If all scripts a properly written, "service foo
status" can also provide something that can be acted upon by
configuration management systems.
Serialization is great (libnv), but it's just gravy. The only feature I
see that's missing is (SMF-style) service management, but for hardware
events, like losing a network link or a disk, can be plugged in to devd
configuration, also easily. Also, in real-life deployments, shutting
down service dependencies is not practical either. For example, if
postfix crashes, I don't want to stop postgey or dovecot. I just want to
nanny postfix back up rather than trying to bring up the whole stack.
Also, forking a shell does not have any significant cost to it when
bringing up something like MySQL, since it's a small fraction of where
the system spends its time to bring up a useful service.
Rewriting scripts in C doesn't provide service management or give any
on-demand (inetd, read: launchd) functionality.
- Nikolai Lifanov
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