Re: Why isn't /bin/sh managed with alternatives?

[Robert Woodcock <rcw@oz.net>]

On Sun, April 5, Shaleh <shaleh@livenet.net> wrote:
> My assumption is that /bin/sh is VERY important to the system.  All
> server scripts use it.  A dangling symlink could be hazardous.  Also,
> some systems initially mount only certain directories.  And /etc is
> sometimes on a different partition entirely.  /bin should stand on its
> own.

*NO* dynamically linked binary (this includes /sbin/init and /bin/sh) will
run without /etc/ld.so.cache:

mercury:~$ strace init
execve("/sbin/init", ["init"], [/* 27 vars */]) = 0
brk(0)                                  = 0x804dde8
open("/etc/ld.so.preload", O_RDONLY)    = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=9333, ...}) = 0
mmap(0, 9333, PROT_READ, MAP_PRIVATE, 3, 0) = 0x4000c000
close(3)                                = 0
open("/lib/libc.so.6", O_RDONLY)        = 3

For the curious, it retrieved that "/lib/libc.so.6" string from
ld.so.cache.

By the way, is ash any faster at sh script processing than bash?
If we made ash the default /bin/sh, would it speed the bootup process any?

Another idea I got on IRC was providing a --background flag to
start-stop-daemon so that daemons could be started in parallel - this
might have quite an effect on SMP systems, and DNS misconfigs would be
more treatable if sendmail started in the background instead of waiting a 
few minutes timing out on stuff before anything else could run.

Or we could just use & to do it.
--
Robert Woodcock - rcw@oz.net
All I want is a warm bed and a kind word and unlimited power.
		-- Ashleigh Brilliant


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