EBS snapshots and LVM2

I've been meaning to try this for a while to see how it goes - use LVM2 to take an "instantaneous" snapshot of an EBS volume and then let AWS take it's time. I found LVM wasn't as quick as I'd like. Also, I have performance tested this either, so I don't know how bad the latency will be. Either way, I think it's an easy way to get a consistent backup:

# prep
export MYAZ="us-east-1a"
export MYINST="i-XXXXXXXX"
# create 1st EBS volume and attach
ec2-create-volume --size 2 --availability-zone $MYAZ
export VOL0="vol-XXXXXXXX"
ec2-attach-volume $VOL0 --instance $MYINST --device /dev/sdf

# create LVM partition 1
fdisk /dev/sdf
# add to LVM
pvcreate /dev/sdf1
# create a volume group
vgcreate vol0 /dev/sdf1
# create a logical volume
lvcreate -l80%FREE -n test vol0
# format it
mke2fs -j -m0 /dev/vol0/test
# mount it
mkdir -p /mnt/vol0/test
mount /dev/vol0/test /mnt/vol0/test

# lock data consistently

# create LVM snapshot
lvcreate -L300M -s -n test2 /dev/vol0/test

# unlock data consistently

# create EBS snapshot
ec2-create-snapshot $VOL0
export VOL0_SNAP="snap-XXXXXXXX"

# remove LVM snapshot
lvremove vol0/test2

# create 2nd EBS volume from snapshot and attach
ec2-create-volume --snapshot $VOL0_SNAP --availability-zone $MYAZ
export VOL1="vol-YYYYYYYY"
ec2-attach-volume $VOL1 --instance $MYINST --device /dev/sdf

# import snapshot as new volume group
vgimportclone -n vol1 /dev/sdg1
# activate new volume group
vgchange -a y vol1
# mount it
mkdir -p /mnt/vol1/test2
mount /dev/vol1/test2 /mnt/vol1/test2

EDIT 2013.02.10: "lock data consistently" - I highly recommend "fsfreeze" which is built into most Linux distributions nowadays.

QoS for Asterisk/PiaF on CentOS with Cisco hard phones & switches

Now that I'm moved into the new office for $WORK, I had to diagnose some phone issues with our new Asterisk based PBX-in-a-Flash phone system. Thankfully, the new office setup is better in a few ways:

1. All jacks in the office are active, with PoE
2. All the switches are the same model number, Cisco WS-C3560G-48PS
3. All the phones are the same model, Cisco SPA504G

After tweaking some SIP settings in PiaF, I found myself looking into QoS. The old office did not have it configured, but I wanted to give it a second look.

Thankfully, Cisco has a QoS feature for those without an CCIE certification - Auto QoS. To enable QoS for our network here, the process was as follows:

! optional: enable debug to watch command macros execute

debug auto qos
! configure the switch

conf t

  ! cdp must be running
  cdp run

  ! first configure all end-user ports

  int range gi0/1 - 42
    cdp enable

    auto qos voip cisco-phone

  ! next configure the PBX port and uplink to other switch

  int range gi0/46, gi0/52
    cdp enable

    auto qos voip trust

  exit

exit

! disable debug

no debug auto qos

And AFAICT that's that. Repeat for all switches and redundant ports for the PBX. For more details, there's a configuration example and additional documentation on Cisco's site.

Rootless Root

ESR's UNIX Koans are always worth reading again... be enlightened!

rsync + FAT32 filesystem

Found a useful nugget in the rsync FAQ: if your destination filesystem when using rsync is a FAT32 filesystem you need to add the --modify-window=1 option due to problems with the modified times on FAT32. A working example would be:

rsync \
 --progress \
 --delete \
 --verbose \
 --archive \
 --modify-window=1 \
 /path/to/source/dir/ \
 /path/to/fat32/dir/

As always, remember to be careful about those trailing slashes!