Allowing ddclient on vyatta to push NAT outside IP to DDNS provider

I have a vyatta vpn appliance sit behind NAT and have a need to use dynamic DNS to update its public IP to dynamic dns provide like no-ip.com. So I ran the suggested commands mentioned in their doc

vyatta@vyatta# set service dns dynamic interface eth0 service dyndns host-name myvyattatestbox.no-ip.org
[edit]
vyatta@vyatta# set service dns dynamic interface eth0 service dyndns server dynupdate.no-ip.com
[edit]
vyatta@vyatta# set service dns dynamic interface eth0 service dyndns login myusername
[edit]
vyatta@vyatta# set service dns dynamic interface eth0 service dyndns password mypassword
[edit]
vyatta@vyatta# commit
[edit]

However, somehow it updated its internal IP of the nic instead of the NAT outside public IP address.

$ show dns dynamic status
interface    : eth0
ip address   : 192.168.0.80
host-name    : myvyattatestbox.no-ip.org
last update  : Wed May 11 04:07:20 2012
update-status: good

It looks like the way that vyatta will update the IP binded to interface though I would expect it to update with the NAT outside address. To let vyatta to update with the NAT outside, we could make a trick on /opt/vyatta/sbin/vyatta-dynamic-dns.pl, replace the line from

     97     #$output .= "use=if, if=$interface\n\n\n";

to
     98     $output .= "use=web, web=checkip.dyndns.com/, web-skip='IP Address: '\n";

By replacing the line, vyatta will query the NAT outside IP against checkip.dyndns.com and then use the polled IP to update against the dynamic DNS provider.

$ show dns dynamic status
interface    : eth0
ip address   : 1.2.3.4
host-name    : myvyattatestbox.no-ip.org
last update  : Wed May 11 05:07:20 2012
update-status: good

Using kpartx to mount partition(s) from disk image.

Scenario:

You got a disk image which was just dumped via dd (e.g. dd if=/dev/hda of=/disk.img). There are 3 partitions on your source disk /dev/hda and they looks like this,


[root@localhost /]# fdisk -l


Disk /dev/hda: 75.1GB, 75161927680 bytes
255 heads, 63 sectors/track, 9137 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes


   Device  Boot      Start       End       Blocks   Id   System
/dev/hda1 *                  1         25       200781  83   Linux
/dev/hda2                   26     1330  10482412+ 82   Linux swap / Solaris
/dev/hda3               1331     9137  62709727+ 83   Linux
 
Now, as long as your disk image /disk.img is a complete dump of /dev/hda, you should be able to mount the partitions within the disk image via loopback device with proper offset value. For e.g.

#### Create the mount point
[root@localhost /]# mkdir -p /chroot/boot

#### Mount the first partition with offset (Start * sectors/track * 512, i.e. 1*63*512)
[root@localhost /]# mount -o loop,offset=$((1*63*512)) /disk.img /chroot/boot
[root@localhost /]# mount | grep /chroot/boot
/disk.img on /chroot/boot type ext3 (rw,loop=/dev/loop1,offset=32256)

So you successfully mounted the first partition (/dev/hda1) and then planning to mount the 3rd partition (/dev/hda3) to /chroot

#### Try mounting the 3rd partition with offset 1331
[root@localhost /]# mount -o loop,offset=$((1331*63*512)) /disk.img /chroot
hfs: unable to find HFS+ superblock
mount: you must specify the filesystem type

Apparently there is something wrong with mount and for some reason it didn't handle offset very well. The util-linux on my box is ver 2.13 which claims to support offset higher than 32bit (well i didn't do any deeper for this specific matters though) but unfortunately it didn't help. As what I want is a quick fix, I come across a tools called "kpartx"which is actually a swiss knife to mount partitions within a disk image file. So here is a demo of how it works.

Solutions:

To list partitions on a disk image. So in this example kpartx see 3 partitions from image disk.img
[root@localhost /]# kpartx -l /disk.img
loop0p1 : 0 401562 /dev/loop 63
loop0p2 : 0 20964825 /dev/loop 401625
loop0p3 : 0 21366450 /dev/loop 21366450

To activate these partitons, we can run kpartx with option -av
[root@localhost /]# kpartx -av /disk.img
add map loop0p1 : 0 401562 linear /dev/loop 63
add map loop0p2 : 0 20964825 linear /dev/loop 401625
add map loop0p3 : 0 21366450 linear /dev/loop 21366450

We can see the device is now mounted as loopback device and presented via /dev/mapper
[root@localhost /]# losetup -a
/dev/loop0: [0800]:49154 (/disk.img)
[root@localhost /]# ls /dev/mapper/loop0p*
/dev/mapper/loop0p1  /dev/mapper/loop0p2  /dev/mapper/loop0p3


Lets see if we could mount these loopback partitions.

[root@localhost /]# mount /dev/mapper/loop0p1 /chroot/boot
[root@localhost /]# mount /dev/mapper/loop0p3 /chroot
[root@localhost /]# mount | grep chroot
/dev/mapper/loop0p1 on /chroot/boot type ext3 (rw)
/dev/mapper/loop0p3 on /chroot type ext3 (rw)

So it looks like the partitions are mounted and file systems on it are recognized without any issue. Let say we finished with the operations on these partitions and now we plan to unmount it and clean it up.

[root@localhost /]# umount /chroot/boot /chroot
[root@localhost /]# losetup -d /dev/mapper/loop0p1
[root@localhost /]# losetup -d /dev/mapper/loop0p2
[root@localhost /]# losetup -d /dev/mapper/loop0p3
[root@localhost /]# kpartx -d /test.img

Pretty much it.

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Reinstalling GRUB after upgrade from Ubuntu 9 to Ubuntu 10.04

So I just upgraded my Ubuntu 9.10 desktop (well, EOL for longtime) to a more recent release, Ubuntu 10.04 LTS Lucid Lynx. So far the upgrade was pretty smooth except it took me like 3 hours to download and complete all the installation files.

Unfortunately it shows something like this after the reboot.

GRUB loading.
error: the symbol 'grub_puts' not found

grub rescue>

So I thought there is something going on with the GRUB during the upgrade, I grep a Ubuntu 10.04 Desktop iso (make sure it is Desktop iso instead of server iso, so that we could boot it up to Live CD mode. ) and boot it up to perform system rescue.

Once the Live CD is booted, I mounted / to somewhere under /mnt

/dev/sda1 on /mnt type ext4 (rw)

I tried chroot to /mnt and run grub-install from there, no dice.

root@ubuntu:/# grub-install  --force /dev/sda
/usr/sbin/grub-probe: error: cannot find a device for /boot/grub (is /dev mounted?).
No path or device is specified.
Try `/usr/sbin/grub-probe --help' for more information.
Auto-detection of a filesystem module failed.
Please specify the module with the option `--modules' explicitly.

So it is apparently the grub-installation on the disk is corrupted or something, I quited from chroot mode and simply run grub-install from the Live CD.

root@ubuntu:~# grub-install --root-directory=/mnt/ /dev/sda
Installation finished. No error reported.

After a reboot my machine is booting without any issue.

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