Re: How do you use the "at" command?

From	Robert Heller <heller@deepsoft.com>
Organization	Deepwoods Software
Subject	Re: How do you use the "at" command?
References	(5 earlier) <pan.2012.01.28.10.27.21@thedarkdesign.free.fr.INVALID> <jg1ddq$cmg$1@dont-email.me> <4f2659fa$0$32272$426a74cc@news.free.fr> <jg7it2$an1$1@dont-email.me> <jg9t72$eqv$3@dont-email.me>
Newsgroups	comp.os.linux.misc
Message-ID	<bK2dnVgrKpPi4rXSnZ2dnUVZ_oudnZ2d@posted.localnet> (permalink)
Date	2012-01-31 17:55 -0600

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At Wed, 01 Feb 2012 00:24:18 +0100 Aragorn <stryder@telenet.be.invalid> wrote:

> 
> Following up on my own post because I realized I've made a logical 
> error... ;-)
> 
> On Tuesday 31 January 2012 03:16, Aragorn conveyed the following to 
> comp.os.linux.misc...
> 
> > On Monday 30 January 2012 09:51, Loki Harfagr conveyed the following
> > to comp.os.linux.misc...
> > 
> >> well, long live Slackware then, good news :-)
> > 
> > Yes, I don't expect Slack to be switching to systemd any time soon.
> > However, since the new udevd release now installs itself under "/usr",
> > the breakage is already introduced, and so sooner or later even
> > Slackware will have to adopt the new udev, and will no longer be able
> > to boot without an initramfs or initrd if you happen to have "/usr" on
> > a separate partition.
> > 
> > Well...  That is to say...  There is a workaround, but this will still
> > require that "/usr" be mounted even when booting up in single-user
> > mode. The workaround is to, instead of using an initrd/initrams - for
> > instance if you roll your own kernels - use a pre-init script which
> > mounts "/usr" (and whatever else you would like it to mount) and then
> > calls the actual init via exec, like so...  (Note: location of GNU
> > Bash and init adapted to the future scenario and using ext4.)
> > 
> >    #!/usr/bin/bash
> >    mount -t -ro ext4 /dev/sda2 /usr
> >    exec /usr/bin/init
> > 
> > You then store this script in, say, "/sbin", and then you invoke it
> > via the kernel's parameter line in the bootloader - for LILO, that's
> > on the "append=" line - like so...
> > 
> >    append="init=/sbin/pre-init.sh"
> > 
> > But of course, that too will break if "/sbin" is going to be a
> > symbolic link to "/usr/sbin".  So they are really pushing the
> > initramfs route.
> 
> There's my logical error, in the contents of the pre-init.sh script.  
> There's no way to invoke "/usr/bin/bash" when "/usr" hasn't been mounted 
> yet, and "mount" itself will then also reside in "/usr/bin".
> 
> So they really _did_ break it in all ways...  One now _must_ use an 
> initramfs or initrd.  I suspect that the initramfs will probably be 
> carrying busybox or something similar to provide for the "mount" and 
> "fsck" commands.

With RHEL 6 / CentOS 6 and recent Fedoras, it is no longer possible to
have /usr on a separate partition from the root file system -- various
bits and pieces on /usr are needed early in the boot process.

Unless you build custom (monolithic) kernels, an initrd is pretty much
needed for modern systems -- SATA disks are in the same boat as SCSI
disks were -- different controllers needing different drivers, plus the
SCSI disk abstraction layer module (sd.ko) is needed.  And with
advanced IDE controllers (what few remain), the same is true.  Only
old-school low-end IDE controllers are supported by the compiled-in IDE
driver. When you add in LVM and/or RAID, you have another module or
three to load, so you need an initrd for that too.  It is pretty much a
given that a modern distro on a modern machine needs to boot with a
initrd or initramfs. 

> 

-- 
Robert Heller             -- 978-544-6933 / heller@deepsoft.com
Deepwoods Software        -- http://www.deepsoft.com/
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Thread

How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 10:16 -0800
  Re: How do you use the "at" command? Lew Pitcher <lpitcher@teksavvy.com> - 2012-01-27 13:43 -0500
    Re: How do you use the "at" command? Lew Pitcher <lpitcher@teksavvy.com> - 2012-01-27 13:45 -0500
      Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-27 15:34 -0600
        Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 22:41 -0800
          Re: How do you use the "at" command? Loki Harfagr <l0k1@thedarkdesign.free.fr.INVALID> - 2012-01-28 10:27 +0000
            Re: How do you use the "at" command? Aragorn <stryder@telenet.be.invalid> - 2012-01-28 19:05 +0100
              Re: How do you use the "at" command? Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2012-01-28 10:26 -0800
              Re: How do you use the "at" command? Loki Harfagr <l0k1@thedarkdesign.free.fr.INVALID> - 2012-01-30 08:51 +0000
                Re: How do you use the "at" command? Aragorn <stryder@telenet.be.invalid> - 2012-01-31 03:16 +0100
                Re: How do you use the "at" command? Aragorn <stryder@telenet.be.invalid> - 2012-02-01 00:24 +0100
                Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-31 17:55 -0600
                Re: How do you use the "at" command? Aragorn <stryder@telenet.be.invalid> - 2012-02-01 02:01 +0100
                Re: How do you use the "at" command? "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2012-01-31 21:36 -0500
                Re: How do you use the "at" command? "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2012-01-31 21:25 -0500
                Re: How do you use the "at" command? Aragorn <stryder@telenet.be.invalid> - 2012-02-01 04:57 +0100
                Re: How do you use the "at" command? Darren Salt <news@youmustbejoking.demon.cu.invalid> - 2012-01-31 23:46 +0000
                Re: How do you use the "at" command? Aragorn <stryder@telenet.be.invalid> - 2012-02-01 02:12 +0100
  Re: How do you use the "at" command? Richard Kettlewell <rjk@greenend.org.uk> - 2012-01-27 19:10 +0000
    Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 11:17 -0800
      Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-27 15:34 -0600
  Re: How do you use the "at" command? unruh <unruh@invalid.ca> - 2012-01-27 20:26 +0000
    Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 22:51 -0800
  Re: How do you use the "at" command? Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2012-01-27 12:23 -0800
    Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-27 15:35 -0600
      Re: How do you use the "at" command? Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2012-01-27 17:22 -0800
        Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-27 20:25 -0600
          Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 22:49 -0800
            Re: How do you use the "at" command? Bit Twister <BitTwister@mouse-potato.com> - 2012-01-28 07:16 +0000
              Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 23:57 -0800
        Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 22:49 -0800
          Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-28 06:07 -0600
            Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-28 13:32 -0800
              Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-28 22:28 -0600
                Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-28 22:50 -0800
                Re: How do you use the "at" command? Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2012-01-28 23:35 -0800
                Re: How do you use the "at" command? unruh <unruh@invalid.ca> - 2012-01-29 18:46 +0000
                Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-29 12:03 -0800
                Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-29 15:38 -0600
                Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-29 16:58 -0800
                Re: How do you use the "at" command? unruh <unruh@invalid.ca> - 2012-01-30 01:36 +0000
                Re: How do you use the "at" command? Aragorn <stryder@telenet.be.invalid> - 2012-01-30 03:07 +0100
                Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-29 19:21 -0800
                Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-29 19:17 -0800
                Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-29 11:48 -0800
                Re: How do you use the "at" command? Robert Heller <heller@deepsoft.com> - 2012-01-29 07:35 -0600
                Re: How do you use the "at" command? Aragorn <stryder@telenet.be.invalid> - 2012-01-29 20:40 +0100
          Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-02-03 13:25 -0800
      Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 22:45 -0800
    Re: How do you use the "at" command? Todd <Todd@invalid.invalid> - 2012-01-27 22:42 -0800

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