The source code can be downloaded and is easy to compile.  But it's most useful if statically-linked, creating a Linux executable file that can run on its own without extra libraries — from a live CD for example.

To create a statically-linked [...]]]> GNU ddrescue is an excellent tool for recovering files from failing hard disks.

The source code can be downloaded and is easy to compile.  But it's most useful if statically-linked, creating a Linux executable file that can run on its own without extra libraries — from a live CD for example.

To create a statically-linked version, run this instead of the usual ./configure:

./configure LDFLAGS=-static --no-create

Then run make in the normal way.

These notes will help you set up IPv6 routing on your local network.

The plan: [...]]]> IPv6 Tunnelling on Linux

This is probably fairly basic stuff, and there are many other webpages with similar information, but here, the information is set out in a way that makes sense to me.  Hopefully it will to others too.

These notes will help you set up IPv6 routing on your local network.

The plan: to enable one of the Linux computers on my home network to handle IPv6 tunnelling and route advertising.  All computers on the local network will then be able to access the IPv6 internet.

Prerequisites:

• An ADSL/Cable/whatever modem/router that does NOT block protocol 41 packets.  If yours does block protocol 41, the tunnel won't work.  I don't know of a specific way of testing whether a router blocks protocol 41.
• A Linux computer on your home network that will act as IPv6 router (don't confuse it with the 'router' that is probably also your ADSL modem and wifi access point).  (No doubt this can be done on Windows too, but don't ask me how).
• An internet connection for the Linux computer with a fixed IP address (not a dynamically allocated one).  I'll refer to that fixed IP address as 5.6.7.8.  Note that this need not be an externally routable address: if the computer is behind a NAT box, and has a local address such as 192.168.1.8, then that's the address to use where these instructions say '5.6.7.8'.  [This is a correction to the previous version of these instructions.]

Assumptions

• Your Linux computer is running a Debian-based system (including Ubuntu and Mint).  If not, you'll need find equivalent versions of some of the commands given here.

Post-requisites

• Once you've got IPv6 networking going, you'll suddenly need an IPv6 firewall, because your computers all now have externally accessible addresses.  This post won't tell you how to do that.

Step 1

Go to Hurricane Electric's tunnelbroker.net and register for a tunnel.  (Other tunnel providers are available).

Hurricane Electric (HE) will allocate a /64 subnet (aka 'prefix') to you, such as 2001:db8:4321:abcd::/64.  (HE's tunnels really start with 2001:470: but I'll use the official example subnet of 2001:db8: in this document.)

Once you've registered, signed in, and created a tunnel, HE's page at www.tunnelbroker.net will list your tunnels (you can have up to five) by their domain names, which will be something like user-1.tunnel.tserv10.par1.ipv6.he.net.

Click on the name of the tunnel to find all sorts of useful details, including:

Note that 1.2.3.4 represents the IPv4 address of the tunnel that has been assigned to you.  And 5.6.7.8 will be replaced by your own external IPv4 address: if you're behind a firewall or ADSL router that does NAT, that's the real-world address of your ADSL router.

The tunnel has two ends, and each end has both an IPv4 address and an IPv6 one.  The IPv4 addresses are your own external address (5.6.7.8) and the one assigned by HE (1.2.3.4).  The IPv6 addresses are in the /64 subnet assigned by HE for the purpose: the far end's address ends in ::1, the local end's address ends in ::2.  No other addresses in that subnet are used.

HE also give you another 'routed' /64 subnet: that's the one you'll use on your LAN.  In this example it's 2001:db8:4322:abcd::/64.

HE provide 'Example Configurations' which list the commands needed to set up the tunnel for a range of operating systems.  I'll use the 'Linux-route2' example:

modprobe ipv6
ip tunnel add he-ipv6 mode sit remote 1.2.3.4 local 5.6.7.8 ttl 255
ip link set he-ipv6 up
ip addr add 2001:db8:4321:abcd::2/64 dev he-ipv6
ip route add ::/0 dev he-ipv6
ip -f inet6 addr

Run those commands (as root), and you should be in business.  Now you can try

ping6 ipv6.google.com

and browsing to sites such as www.kame.net, where the famous dancing turtle confirms that you're using IPv6.

To make those settings permanent you can add them to /etc/rc.local (or whichever file your version of Linux uses for locally-configured start-up commands). 

Step 2

Step 2 involves sharing the IPv6 goodness with other computers on your network. 

First, activate IPv6 packet forwarding on your 'router' with these commands:

sudo sysctl -w net.ipv6.conf.all.forwarding=1
sudo echo net.ipv6.conf.all.forwarding=1 >> /etc/sysctl.conf

The first of those commands enables forwarding now; the second makes the change permanent so that the setting will still be there after the computer is rebooted.

The Route Advertising Daemon radvd is what I used.  Install the radvd package, and then create /etc/radvd.conf containing something like this (taken from tomicki.net):

interface eth0
{
    AdvSendAdvert on;
    MinRtrAdvInterval 5;
    MaxRtrAdvInterval 15;     

    prefix 2001:db8:4322:abcd::/64
    {
        AdvOnLink on;
        AdvAutonomous on;
    };
};

Start the radvd daemon (with sudo /etc/init.d/radvd start on Debian).  And then try accessing IPv6 from other computers on your LAN — magically, it works!  Windows Vista/7 computers will have to have teredo tunnelling turned off first, otherwise they'll use that instead of your own tunnel.  I'm not sure how Windows XP handles this.

What to do next

This is just the beginning of life with IPv6.  You'll want to go on to play with:

• an IPv6 firewall, i.e. ip6tables settings, possibly wrapped in a more user-friendly scripting language such as ferm.
• more control over address allocation, using a DHCPv6 server such as dibbler.

It creates output that starts like this:

It turned out that the problem was really with my use of local signal handlers.

The following code works with 5.10.1 but not with 5.14.2:

#!/usr/bin/perl use strict; use warnings; print "starting pid=$$\n"; my $I = 0; {   my $pid [...]]]> A Perl script that I've been working on wasn't working properly with Perl 5.14.2.

It turned out that the problem was really with my use of local signal handlers.

The following code works with 5.10.1 but not with 5.14.2:

#!/usr/bin/perl
use strict;
use warnings;
print "starting pid=$$\n";
my $I = 0;
{
  my $pid = 0;
  sub handler {
    my $sig = shift;
    $I += 1;
    print "caught $sig\n";
    local $SIG{$sig} = 'IGNORE'; # doesn't work with local!!
    kill($sig, -$$);
    print "end of handler\n";
  }
  local $SIG{INT} = \&handler;
  kill('INT', $$);
}
print "ending I=$I\n";

With 5.10.1, it calls handler() twice and then exits with I=2; with 5.14.2 it calls the handler many times before crashing with a segfault.

Removing the local from the inner $SIG{$sig} allows it to work with 5.14.2, which makes sense if I'm right in thinking that that command changes the immediately-containing signal handler, and not the global one.

I found the Perl documentation a bit vague on this topic, so this is here in case it's useful to someone else.

So I installed Xubuntu 11.10 (I like XFCE).

And it all just worked out of the box — wifi, webcam, sound etc.

Except for sleep and hibernation.  I [...]]]> This was for a client who only needs the basics — email, typing, web browsing — and doesn't have time to adapt to a trendy new GUI.

So I installed Xubuntu 11.10 (I like XFCE).

And it all just worked out of the box — wifi, webcam, sound etc.

Except for sleep and hibernation.  I tried all sorts of fixes and troubleshooting, but nothing worked.  The screen goes blank, but it doesn't turn off.  After being forced off, it resumes as though sleep or hibernation had worked.  Couldn't solve it, so I just changed the settings to never try to sleep or hibernate.

I wanted to bring it up to date, and knew that the client wouldn't want the look-and-feel of it to change radically, so to avoid Unity and Gnome 3, I decided [...]]]> I was working on a client's laptop, on which I'd installed Ubuntu 9.04 a few years ago and it hadn't been updated since then.

I wanted to bring it up to date, and knew that the client wouldn't want the look-and-feel of it to change radically, so to avoid Unity and Gnome 3, I decided to install Xubuntu 11.10.

I backed everything up, expecting to do a clean install of the new system.  But the Xubuntu installer offered to upgrade directly from 9.04, so I tried it, and it worked! 

The only minor glitch was that Thunderbird didn't find the old profile.  I had to rename ~/.mozilla-thunderbird to ~/.thunderbird, and then that worked too.

It seems that the getopt() method messes up the global @ARGV array even if I pass it a copy.

For example:  

#!/usr/bin/perl use strict; use warnings; use AppConfig; my $opts = AppConfig->new( { CASE   => 0, } ); $opts->define('config=s', {DEFAULT => ''}); print "ARGV: @ARGV\n"; [...]]]> I've been playing with the Perl AppConfig module (http://search.cpan.org/~abw/AppConfig-1.66/lib/AppConfig.pm)

It seems that the getopt() method messes up the global @ARGV array even if I pass it a copy.

For example:
 

#!/usr/bin/perl
use strict;
use warnings;
use AppConfig;
my $opts = AppConfig->new( { CASE   => 0, } );
$opts->define('config=s', {DEFAULT => ''});
print "ARGV: @ARGV\n";
my $argvCopy = [@ARGV];
print "argvCopy: @$argvCopy\n";
$opts->args($argvCopy);
print "after args() ARGV: @ARGV\n";
$opts->getopt(qw(auto_abbrev), $argvCopy);
print "after getopt() ARGV: @ARGV\n";

produces this output

# appconfig-error.pl --config xyz 123 abc
ARGV: --config xyz 123 abc
argvCopy: --config xyz 123 abc
after args() ARGV: --config xyz 123 abc     # @ARGV is still complete
after getopt() ARGV: 123 abc                # @ARGV has bits missing

This is a problem because I need to call getopt() twice — once to get at the –config option, then I read the configuration file with the file() method, then I re-read the command line options so that they override the ones in the configuration file.

Using args() is OK — @ARGV is preserved — but I need the extra feature of getopt().

I've emailed the author, so I'll wait to see what his reply is.

Installing it as a printer on Xubuntu 11.10 was straightforward, once I'd done a bit of research.

Panasonic give instructions for Redhat [...]]]> Notes on the Panasonic KX-MB2000E.

The printer — sorry, it's not a printer, it's a <q>Document System</q> — has a web interface: the user name is 'root' and the default password is '1234'.

Installing it as a printer on Xubuntu 11.10 was straightforward, once I'd done a bit of research.

Panasonic give instructions for Redhat here: http://panasonic.cn/support/download/manual/files/Linux_Install_for_KX-MB2000_series.pdf.

This is what I did on a laptop running Xubuntu 11.10:

1. Download three .rpm files from http://www.panasonic.net/pcc/support/fax/common/table/linuxdriver.html
2. Use alien to convert them to do .deb files.
3. Use dpkg -i to install them.
4. Connect the printer (I did it on the LAN).
5. Use CUPS to set up the printer: when it asks for a PPD file, use the one in /usr/share/cups/model/kxmb2000.ppd.
6. Done.

The scanner was more tricky — research suggested that it couldn't be done, and SANE had no reference to it.  But as the printer is capable of scanning to an FTP account or a Samba share, I set up a 'Scans' folder with write access via Samba, and entered the details on the printer (via the web interface or the buttons on the front).  And it works!  Pressing the Scan button and choosing SMB in the printer menu puts a PDF file in the Scans folder.  There's little or no control over scanning settings, but it's a start.

I tried to add this information to openprinting.org, but every time I try to log in there, I just get an empty page.

http://www.hiren.info/pages/bootcd

but you can’t download it from there. Googling for it brings up all sorts of nonsense pages about bit-torrents that don’t work. The actual download source can be hard to find, so here’s the link:

http://www.hirensbootcd.org/download/