IPv6 right now.

Reading slashdot I saw an article about the coming IPv4 Apocalypse. So I figured I should spend some time getting up to speed. And when I say "getting up to speed" I think I really mean "hack at it a little."

First I need some routable addresses. My ISP at home is Bell, which is probably going to be the last ISP in the universe to hand out IPv6 addresses. So I need a 6to4 tunnel. I found handy guide for Linode which basically said "get a free tunnel from HE." Which I did.

The following was added to /etc/sysconfig/network on the VM I wanted to be my IPv6 router

IPV6_DEFAULTDEV=sit1

IPV6FORWARDING=yes

IPV6_ROUTER=yes

Next I added he following to /etc/sysconfig/network-scripts/ifcfg-sit1

DEVICE=sit1

BOOTPROTO=none

ONBOOT=yes

IPV6INIT=yes

IPV6TUNNELIPV4=IPv4

IPV6ADDR=A1:B1:C1::2

Where IPv4 is the IP Bell gave me and A1:B1:C1::2 the client IPv6 address from HE.

ifup sit1

ping6 -n ipv6.chat.freenode.net

yay! It works.

Next, I want other computers to be able to access this tunnel. This took some messing around, but by blindly stabbing at it I got it going.

Then I asked for a /48, and added this to /etc/sysconfig/network-scripts/ifcfg-eth0

IPV6INIT="yes"

IPV6ADDR=A2:B2:C2::2

Where A2:B2:C2::2 is part of my Routed /48 from HE.

Then service network restart.

Next, on my desktop computer, I added the following to /etc/sysconfig/network

NETWORKING_IPV6=yes

Then to /etc/sysconfig/network-scripts/ifcfg-eth0

IPV6INIT=yes

IPV6ADDR=A2:B2:C2::6

Then:

ifdown eth0 ; ifup eth0

ping6 A2:B2:C2::2

YAY! That works.

But... what about routing and forwarding and so on? This is where I stabbed around blindly. The solution was to use radvd.

/etc/radvd.conf:

interface eth0

{

    AdvSendAdvert on;

    MinRtrAdvInterval 30;

    MaxRtrAdvInterval 100;

    prefix A2:B2:C2::/64

    {

        AdvOnLink on;

        AdvAutonomous on;

        AdvRouterAddr on;

    };

};

Start the service, then restart eth0 on corey, and bingo! I can surf to ipv6.google.com.

Todo : Setup reverse DNS for my /48. Setup ipv6 for all my computers. Figure out how to tell HE when Bell changes my IP. They have a tool to do this but my first attempt didn't work.

And of course understand what it is I'm doing. For instance, if IPv6 uses 128bit IPs, surely the /64 would be enough

Watch that command

I was reminded to day of how useful watch is. I omitted it from my previous list of important and useful commands because I rarely use it. But today I had George open on the bench and was finding out what fan connectors on the motherboard corresponded to which speed sensor, as reported by lm-sensors.

watch -n 0 "sensors w83793-i2c-0-2f | grep fan"

Then, as I plugged and unplugged a 3-wire fan here and there, I could see on screen what was going on. This is especially important, cause you don't want to unplug the CPU fan for any length of time.

FYI, the sensor:fan port mapping for a DSBV-DX is as follows:

fan1  CPU_FAN1

fan2  CPU_FAN2

fan3  FRNT_FAN1

fan4  FRNT_FAN2

fan5  FRNT_FAN3

fan6  FRNT_FAN4

fan7  REAR_FAN1

fan8  REAR_FAN2

fan9  FBD_FAN1

fan10 N/C

fan11 N/C

fan12 N/C

I take it back

The war on noise continues apace. Next up, remove Jimmy from service, replacing it with George.

# fdisk -H 224 -S 56 /dev/sdd  

# fdisk -H 224 -S 56 /dev/sde

# sfdisk -l /dev/sdd



Disk /dev/sdd: 182401 cylinders, 255 heads, 63 sectors/track

Warning: The partition table looks like it was made

  for C/H/S=*/224/56 (instead of 182401/255/63).

For this listing I'll assume that geometry.

Units = cylinders of 6422528 bytes, blocks of 1024 bytes, counting from 0



   Device Boot Start     End   #cyls    #blocks   Id  System

/dev/sdd1          0+ 233598  233599- 1465132900   fd  Linux raid autodetect

/dev/sdd2          0       -       0          0    0  Empty

/dev/sdd3          0       -       0          0    0  Empty

/dev/sdd4          0       -       0          0    0  Empty

sdd and sde are a pair WD15EARSs. With 4k blocks. Normaly I use sfdisk -d to copy partitions, but that failed on 4k blocks.

mdadm -C -n 2 -l 1 /dev/md2 /dev/sdd1 /dev/sde1

pvcreate /dev/md2

pvs -o name,pe_start

vgcreate -s 32M T00 /dev/md2

lvcreate -l 99%VG --name LV00 T00

mkfs -t ext4 -E stride=32 -m 1 -O extents,uninit_bg,dir_index,filetype,has_journal /dev/T00/LV00 

tune4fs -c 0 -i 0 /dev/T00/LV00

I got the formating commands from I Do Linux. I read up on all those mkfs options. I'd never have guessed they were the "best" options to use.

The tune4fs is basically turning off the fsck that happens automatically every X days or Y reboots; fsck is SLOW, and the automatic fsck always happens when you least want it. And with journals, UPSes and so on, an unsafe shutdown isn't supposed to happen.

I left some space on the VG free so I could do snapshots.

But then I got to thinking. Blocking off one large LV means that the file server VM gets access to the entire disk and all that space can't be used by a different VM or the host for another purpose. With LVM, I can grow the LV if I need it. So why not give it 500G at a time?

e4fsck -f /dev/T00/LV00 

resize4fs -p /dev/T00/LV00 500G 

lvresize -L 500G -t -v /dev/T00/LV00 

resize4fs -p /dev/T00/LV00

This was as much a test of ext4 resizing as anything else. And it worked flawlessly. Btw, fsck on an empty FS is fast.

So what does it look like:

# df -h

Filesystem            Size  Used Avail Use% Mounted on

/dev/mapper/G00-root  572G  537G  5.8G  99% /

/dev/md0              950M   31M  870M   4% /boot

tmpfs                 5.9G     0  5.9G   0% /dev/shm

/dev/mapper/T00-LV00  493G  493G     0 100% /T00

WHAT 100% FULL ALREADY?

Well, no. I wanted to make sure the 500G as resize4fs sees it and 500G as lvresize sees it were the same thing, so I filled the FS to the brim:

# dd if=/dev/zero of=/T00/HUGE

dd: writing to /T00/HUGE': No space left on device

1031717425+0 records in

1031717424+0 records out

528239321088 bytes (528 GB) copied, 6608.14 seconds, 79.9 MB/s

See that? Bare in mind that this dd was happening during the initial RAID build. I hypothesis that the mobo in Corey (ASUS M2N-MX SE) that I was doing the previous tests on SUCKS. And that the mobo in George (ASUS DSBV-DX) does not.

# time rm -f /T00/HUGE

real    0m31.020s

user    0m0.000s 

sys     0m20.302s

It's a server, not a telephone!

Dear the people at Red Hat,

I'm trying to set up a VMware server on top of CentOS 5.5. I want / to be LVM on top of RAID5, /boot as RAID also. I want as few packages installed as possible, only the bare minimum services running. This seems like simple but widespread scenario.

But why did it take me 3 hours?

Why did LVM on RAID5 require a bleeding graphical install? This is a server we're talking about.

Why did a huge pile of useless stuff like bluetooth, pcsc, xfs (?!), nfs, cups, wpa_supplicant, tux, apache, nscd, IRDA get installed? If I need these things, yum allows me to install them in seconds. Instead I spend an hours hunting down those and other useless bits.

Maybe I'm just getting old. But I pine for Redhat 9, where everything was small, simple, understandable. Now everything is 5 levels of indirections, lots of smoke and a dash of magic.

Grrrrrr!

-Philip

Silence!

Newegg.ca sent me email yesterday with a tracking number. Click on it and BUH "we have no information about this package." Yes, you are idiots.

But this morning, I try again at 8h00. And BUH PACKAGE ON TRUCK IN SHERBROOKE!

So I don't go back to bed, wait impatiently for the truck to show up. Three cheers for eCommerce!