Ubuntu LVM on Software RAID

I've been playing with LVM and software RAID on Ubuntu. Install the packages:

apt-get install lvm2 dmsetup mdadm 

After doing the above you'll want to reboot with your new initrd so that you have the kernel modules to do an lvcreate later. I've got a cheap USB device which I'll set up with software RAID1 on two partitions for fun:

$ fdisk /dev/sdb
...
Command (m for help): p

Disk /dev/sdb: 257 MB, 257949696 bytes
8 heads, 62 sectors/track, 1015 cylinders
Units = cylinders of 496 * 512 = 253952 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         505      125209   fd  Linux raid autodetect
/dev/sdb2             506        1010      125240   fd  Linux raid autodetect  

Create the RAID1 device from the partitions:

$ mdadm --build /dev/md0 --level=1 --raid-devices=2 /dev/sdb{1,2}
mdadm: array /dev/md0 built and started.
$ 

Make a file system on the new device while I watch the RAID sync:

$ mkfs -j /dev/md0 &
$ while [ 1 ]; do cat /proc/mdstat; sleep 4; done
Personalities : [raid1] 
md0 : active raid1 sdb2[1] sdb1[0]
      125209 blocks super non-persistent [2/2] [UU]
      [==================>..]  resync = 91.0% (114944/125209) finish=0.3min speed=506K/sec
      
unused devices: 
Personalities : [raid1] 
md0 : active raid1 sdb2[1] sdb1[0]
      125209 blocks super non-persistent [2/2] [UU]
      [==================>..]  resync = 92.6% (116928/125209) finish=0.2min speed=504K/sec
      
unused devices: 
....
Personalities : [raid1] 
md0 : active raid1 sdb2[1] sdb1[0]
      125209 blocks super non-persistent [2/2] [UU]
      [===================>.]  resync = 99.1% (125120/125209) finish=0.0min speed=519K/sec
      
unused devices: 
Personalities : [raid1] 
md0 : active raid1 sdb2[1] sdb1[0]
      125209 blocks super non-persistent [2/2] [UU]

Mount the new filesystem to test it. Then umount it.

$ mount /dev/md0 /mnt/data/
$ df -h /mnt/data/
Filesystem            Size  Used Avail Use% Mounted on
/dev/md0              119M  5.6M  107M   5% /mnt/data
$ umount !$

Add the RAID to an LVM by creating a physical volume, a volume group then a logical volume:

pvcreate /dev/md0
vgcreate volgroup00 /dev/md0
lvcreate -n logvol00 -l 30 volgroup00

Remember physical volumes get added to volume groups and then we add logical volumes so I'm going through the above steps quickly to make it clear how the above are linked together. You can {pv,vg,lv}display at each step of the above as appropriate (that's how I got 30 extents). Make a filesystem and then mount your volume:

mkfs -j /dev/volgroup00/logvol00
mount /dev/volgroup00/logvol00 /mnt/data/

Now we want to extend it in a very inconvenient way (for sadism). We'll undo everything and build it again but with two smaller RAID1 devices... it's funny if you pretend you're in a Monty Python script. Note the LVM stack going back down in reverse:

lvremove /dev/volgroup00/logvol00
vgremove volgroup00
pvremove /dev/md0

Disassemble your RAID device and verify that it's gone:

mdadm -S /dev/md0
cat /proc/mdstat

Finally go back to fdisk and delete your partitions and rebuild them in quaters:

$ fdisk -l /dev/sdb

Disk /dev/sdb: 257 MB, 257949696 bytes
8 heads, 62 sectors/track, 1015 cylinders
Units = cylinders of 496 * 512 = 253952 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         253       62713   fd  Linux raid autodetect
/dev/sdb2             254         506       62744   fd  Linux raid autodetect
/dev/sdb3             507         759       62744   fd  Linux raid autodetect
/dev/sdb4             760        1012       62744   fd  Linux raid autodetect
$

Now create two RAID1 devices:

$ mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb{1,2}
mdadm: array /dev/md0 started.
$ mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sdb{3,4}
mdadm: array /dev/md1 started.
$ 

It will be syncing md0 first and then md1, but we can go on:

$ cat /proc/mdstat 
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md1 : active raid1 sdb4[1] sdb3[0]
      62656 blocks [2/2] [UU]
        resync=DELAYED
      
md0 : active raid1 sdb2[1] sdb1[0]
      62592 blocks [2/2] [UU]
      [=========>...........]  resync = 48.3% (30720/62592) finish=1.0min speed=498K/sec

Add the first RAID device to a physical volume:

$ pvcreate /dev/md0
  Physical volume "/dev/md0" successfully created

but don't add the second one yet, we'll do that later to extend. Next create a volume group and then a logical volume. Then we make a file system and mount it:

vgcreate volgroup /dev/md0
lvcreate -n data -l 15 volgroup
mkfs -j  /dev/volgroup/data
mount /dev/volgroup/data /mnt/data/

Copy some awesome music to your new LVM (What's LVM practice without early 90's metal?):

cp ~/tunes/disincarnate/Dreams\ of\ the\ Carrion\ Kind/* /mnt/data/

You might even want to play one of the songs on your device as you extend the volume. Add the other RAID device as an available physical volume for LVM and then extend volgroup to use it:

pvcreate /dev/md1
vgextend volgroup /dev/md1

vgdisplay will show that you have more space. Note also the current size of /mnt/data:

$ vgdisplay | grep 15
  Alloc PE / Size       15 / 60.00 MB
  Free  PE / Size       15 / 60.00 MB
$ df -h /mnt/data | grep M
Filesystem            Size  Used Avail Use% Mounted on
                       59M   52M  4.0M  93% /mnt/data
$ 

Extend volgroup into the extra 15 extents:

$ lvextend -l +15 /dev/volgroup/data 
  Extending logical volume data to 120.00 MB
  Logical volume data successfully resized
$

Then extend the filesystem (while listening the the music on the same filesystem):

$ resize2fs /dev/mapper/volgroup-data
resize2fs 1.40.2 (12-Jul-2007)
Filesystem at /dev/mapper/volgroup-data is mounted on /mnt/data; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/mapper/volgroup-data to 122880 (1k) blocks.
The filesystem on /dev/mapper/volgroup-data is now 122880 blocks long.

$

Note the new size:

$ df -h /mnt/data | grep M
Filesystem            Size  Used Avail Use% Mounted on
                      117M   52M   60M  47% /mnt/data
$

Now I've got a USB device with four partitions and each pair is in a RAID1 as well as the member of an LVM full of obscure metal. What else should one have in his pocket?

rhel xen

I've played with xen on Ubuntu and now I'm going to try it the RedHat way. So far I've installed my system with the virtualization option checked. This option seems to install tools like virt-manager and the xen kernel:

$ uname -a
Linux xen0.domain.tld 2.6.18-53.el5xen #1 SMP Wed Oct 10 
16:48:44 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux

I'm now reading the RedHat's Virtualization Guide.

extra swap files

It's easy to add extra swap space. Create some 2G blob files (assuming 32 bit):

 dd if=/dev/zero of=/var/xswap/xswap1 bs=1M count=2048

Make them swap files:

 mkswap /var/xswap/xswap1

Tell the OS to swap to them:

 swapon /var/xswap/xswap1

If "swapon -s" shows that it's working, then update /etc/fstab:

/var/xswap/xswap1  swap  swap  defaults  0 0

You can do this for as many swap files as you have disk for. As of the 2.6 kernel swap files are just as fast a swap partitions. So, the flexibility of a swap file is a better choice even with LVM.

things to learn

I would like to know more about the following: udev tune2fs kickstart pam_ldap xm

Darwin Streaming Server on GNU/Linux

Darwin Streaming Server is an Apple Public Source Licensed version of QuickTime Streaming Server technology for streaming QuickTime and MPEG-4 media to clients with RTP and RTSP from a GNU/Linux host. You can untar it in /opt and simply run "./Install". After setting an admin password the web admin interface will be running on port 1220. Then you can point a Quicktime client at:

 rtsp://server.domain.tld:7070/sample_300kbit.mov

Note that it's easy to overlook that you need to use port 7070. Using just the RTSP protocol with no port numbers seems to direct me to port 554 which is easy to confuse as the correct port when searching for network activity from a client (123.456.8.9):

$ netstat -an | grep tcp | fgrep 123.456.8.9
tcp        0      0 123.456.7.8:554            123.456.8.9:1733
    CLOSE_WAIT
tcp        0      0 123.456.7.8:554            123.456.8.9:1735
    CLOSE_WAIT
tcp        0      0 123.456.7.8:80             123.456.8.9:1736
    TIME_WAIT
$ fuser -n tcp 554
here: 554
554/tcp:             13052
$ ps axu | grep 13052
qtss     13052  0.0  0.0 70188 5144 ?        Sl   16:23   0:00
/usr/local/sbin/DarwinStreamingServer
root     13316  0.0  0.0  4224  660 pts/2    S+   17:13   0:00 grep 13052
$ 

Note that the above shows what I think to be reasonable troubleshooting for seeing if a desired service is listening on a port but it mislead me. I tried opening the above in Totem but I would need restricted codecs.

twitter

Some of my friends are using twitter. I'm going to try leaving gTwitter up. I see there's a python-twitter so perhaps I'll write a command line twitter for fun.

fuser

fuser - identify processes using files or sockets. Handy:

• Kick users off of your system. Use 'w' to see what /dev/pts/# they have and then kill that process:

  w
  fuser -k /dev/pts/1
  

• Find out who's using a service by port. E.g. apache processs:

  $ fuser -n tcp 80
  here: 80
  80/tcp:     22502 22505 22506 22507 22508 22509 22510 22511 22512 23548 27933
  

  A lot like ps axu | grep httpd but while loops are like for loops too. Obvious next steps... who's using SSH? fuser -n tcp 22
• Determine why a file system is busy

OSSTMM

Open Source Security Testing Methodology Manual

Cisco SMTP Inspection

I mentioned earlier about strange sendmail bugs. Turns out it was a firewall issue. Cisco firewalls have a problem with ESMTP transactions if fixup smtp (mailguard) is enabled. The IOS command no fixup protocol smtp 25 should disable it.