A few questions from a current linux user

Sat Aug 9 01:28:32 UTC 2008

On Thu, 7 Aug 2008 23:20:08 -0400, "Krishna Mohan Gundu" <gkmohan at gmail.com> wrote:
> Hi,
> I am currently using Fedora Core 4 linux distribution for my everyday
> needs like programming, checking emails etc on my two year old HP
> laptop. I feel that time has come for me to move away from Fedora. I
> wasted a lot of time compiling libraries and their dependencies. I
> could benefit from better packaging systems that come with systems
> like FreeBSD.

Hi Krishna,

I've been meaning to respond to this post for a couple of days, but it
took me a little longer than I originally hoped...

This may be totally unrelated to the real question, but doesn't Fedora
use pre-compiled packages by default?  I thought that was pretty much
the One True Way(TM) of updating Fedora systems.

> I tried to gather as much information as I could from the
> documentation available on freebsd.org, but the following questions
> remain unanswered. I would be glad if you can take time to educate me
>
> 1) Is a feature similar to magic SysRq in linux necessary for FreeBSD?
> (As I understand there is no such feature in FreeBSD)

Not really.  SysRq has a few nice characteristics, i.e. it can unmount
local filesystems gracefully to avoid `fsck' runs during the next boot.
It's a nice, handy tool in some cases.  But it also comes at a cost: it
modifies the in-memory state of the running kernel.

FreeBSD has a kernel debugger that can be enabled, called DDB.  When the
kernel locks up or panics because something bogus happened, the DDB can
dump the state of the kernel into a preconfigured swap area, and the
startup scripts of the next boot will pick up the kernel coredump from
swap, save it in `/var/crash', and let you run post-mortem analysis on
the kernel core dump.

If this is combined with something like SysRq, and there's really a bug
in the parts of the kernel that SysRq has to use to perform its final
steps, you lose.  You may be modifying the parts of the kernel memory
that actually exhibit the bug, and make the kernel dump unusable.

> 2) Is it possible to compile multiple versions of gcc? If so what is
> the best way to do it?

Yes, of course.

The "base system" of FreeBSD includes _one_ version of gcc, installed as
`/usr/bin/gcc', but this does not mean that you are limited to *that*
version only.  You can use the Ports tree to install one or more
versions.  The snapshot of Ports I have on the laptop I am using to type
this includes 12 different gcc ports (and that does not include the
Fortran, Objective C, or Java backends GCC supports):

  # pwd
  /usr/ports/lang
  # ls -ld gcc* | nl
       1  drwxr-xr-x  3 root  wheel  - 512 Jul 17 03:01 gcc-ooo
       2  drwxr-xr-x  3 root  wheel  - 512 Jul 17 03:01 gcc28
       3  drwxr-xr-x  3 root  wheel  - 512 Jul 17 03:01 gcc295
       4  drwxr-xr-x  3 root  wheel  - 512 Jul 17 03:01 gcc32
       5  drwxr-xr-x  3 root  wheel  - 512 Jul 22 05:03 gcc33
       6  drwxr-xr-x  3 root  wheel  - 512 Jul 29 04:46 gcc34
       7  drwxr-xr-x  3 root  wheel  - 512 Jul 17 03:01 gcc41
       8  drwxr-xr-x  3 root  wheel  - 512 Jul 17 03:01 gcc41-withgcjawt
       9  drwxr-xr-x  3 root  wheel  - 512 Jul 22 05:03 gcc42
      10  drwxr-xr-x  3 root  wheel  - 512 Jul 17 03:01 gcc42-withgcjawt
      11  drwxr-xr-x  3 root  wheel  - 512 Jul 29 04:46 gcc43
      12  drwxr-xr-x  3 root  wheel  - 512 Aug  7 02:25 gcc44
  #

So yes, you can install several different versions of GCC at the same
time.

> 3) Is it possible to perform a binary update from one release to
> another? If so can you please point me to the documentation? How are
> config files updated in this case? (Could not locate documentation on
> binup)

Yes.  In recent FreeBSD releases, the "base system" of FreeBSD includes
freebsd-update.  This is a utility authored by Colin Percival, who is
currently the Security Officer of FreeBSD, and a very smart fellow :)

What freebsd-update does is described in its manpage

    http://www.freebsd.org/cgi/man.cgi?query=freebsd-update&format=ascii

but the basic idea is that is can do one of the following things:

    * Download binary update packs in `/var/db/freebsd-update'.  These
      are not installed immediatelly, so you can periodically pull the
      binary update files and install them later, when you have the time
      for an upgrade.

      The default `fetch' mode of `freebsd-update' downloads binary
      updates for the release & branch of FreeBSD that you have
      installed on the local system.  Staying on the same branch has
      various advantages that are nicely described in the online article
      about `

    * Download binary update packs for _upgrading_ to a new release.
      This is slightly different from an update that sticks to a single
      FreeBSD release-branch, and there are official release notes about
      the changes of every major release.  They are published online at

          http://www.FreeBSD.org/releases/

      Downloading the binary packs for new release still does *not*
      install or upgrade anything.

    * The final important feature of freebsd-update is that it can use
      the latest snapshots you have fetched in `/var/db/freebsd-update'
      to perform a binary upgrade of the FreeBSD base system.

> 4) If a binary update leads to an unstable system, how easy it is to
> backtrack to an earlier working version along with working config
> files?

That's probably not very easy.  But freebsd-update is not really going
to pull `unstable' stuff because of the way FreeBSD branches work.  If
you are following a ``FreeBSD-X.Y-STABLE'' release branch, it is pretty
much a given that the source tree should build at all times, and that
the resulting base system should be backwards compatible with all the
binary programs that were produced in any version between the time
``FreeBSD-X.Y-RELEASE'' was cut and your -STABLE snapshot was built.

Having said that, of course, using some sort of backup tool is never a
bad idea.  Even if freebsd-update does nothing to harm your FreeBSD
installation, there are hardware failures, power outages at the worst
possible moment, fat-fingered commands that remove or change slightly
more files that originally intended, and so on.

> 5) Does FreeBSD have support for PCMCIA-USB cards?

Yes, FreeBSD supports PCMCIA (PC-CARD or Cardbus) and USB devices.

FreeBSD includes drivers for various devices of these two types, but
before buying a PC-CARD device you should always check to see if there
is a `high level' driver for the one you are buying.  The generic
PC-CARD, Cardbus and USB layer of the FreeBSD kernel supports the common
`base functionality' of attaching and detaching a device, but to get any
random device to work you need a driver that recognizes it and attaches
to it.

This is a long way of saying that ``Yes, we have PCMCIA and USB support
in the kernel, but you should first check the hardware compatibility
lists and the manpages of your system to see if a particular device is
supported at all, partially supported, or completely unsupported''.

This may be tricky if you can only get hold of the device *after* buying
it and unpacking it, but I've had various levels of success by asking at
computer stores for a ``local test'' with my laptop.  In some of the
local places, I've had *very* helpful responses.  The local sales people
have often told me "We don't have an unpacked version of *that* today,
but if you can wait until Monday, we are getting a new delivery.  When
we unpack a sample / demo of this particular card/adapter/gadget, you
can definitely try it and see how things work."

> PS: I am considering Debian as another alternative.

Debian is a Linux distribution.  A very good one too.  If that fits your
job better than FreeBSD does, it's definitely not a shame to use it.
FreeBSD will still be around if you need it later :-)

Finally, since you are coming from a Linux background, you should spend
some time to check out the excellent documentation FreeBSD contributors
have written over the years.  There are lists of books and articles at

    http://www.freebsd.org/docs.html

You should probably start with some of these:

[1] "The FreeBSD Handbook"
    http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/index.html

[2] "The FreeBSD FAQ (Frequently Asked Questions)"
    http://www.freebsd.org/doc/en_US.ISO8859-1/books/faq/index.html

[3] "Choosing the FreeBSD Version That Is Right For You"
    http://www.freebsd.org/doc/en_US.ISO8859-1/articles/version-guide/index.html

[4] "Explaining BSD"
    http://www.freebsd.org/doc/en_US.ISO8859-1/articles/explaining-bsd/index.html

[5] "FreeBSD: An Open Source Alternative to Linux"
    http://www.freebsd.org/doc/en_US.ISO8859-1/articles/linux-comparison/index.html

[6] "FreeBSD Quickstart Guide for Linux Users"
    http://www.freebsd.org/doc/en_US.ISO8859-1/articles/linux-users/index.html

[7] "FreeBSD First Steps"
    http://www.freebsd.org/doc/en_US.ISO8859-1/articles/new-users/index.html