Few days ago i wanted to make liveusb with kali linux (i had backtrack before). I used this guide to install kali, but i observed, that persistence partition does not work. There is partitions on my usb drive:

When init script found persistent partition and tried to mount  their return error “mount: mounting /dev/sdaX on /root/lib/live/mount/persistence/sdaX failed: Device or resource busy”.
I think this happened because official guide suggest to write iso9660 image on usb drive, and init script think that it is cd drive and mount whole usb device, not a partition where iso placed. This i found in boot.log:

There you can see, that after kali boot, usb drive (sda) still mounted, and i can not mount second partition:

After that whole usb drive is busy.  I attached boot.log to this post with enabled debug, may be it will help someone to fix that.

I decided to make bootable usb disk instead of flashing iso on it. For doing that i used extlinux and original kali iso file.
First i create 2 partitions on usb drive, one for kali and second for persistent files:

Do not forget to set bootable flag on first partition and correct label for persistent paririon.
After that, install mbr from extlinux:

$ dd if=/usr/lib/extlinux/mbr.bin of=/dev/sda
0+1 records in
0+1 records out
440 bytes (440 B) copied, 0.00126658 s, 347 kB/s

Copy kali linux on first partition:

$ mkdir /mnt/sr0 /mnt/kali
$ mount /dev/sr0 /mnt/sr0/
mount: block device /dev/sr0 is write-protected, mounting read-only
$ mount /dev/sda1 /mnt/kali/
$ rsync -a /mnt/sr0/* /mnt/kali

Also i modify boot menu and add entry with persistence boot option at live.cfg:

label live-686-pae-persistence
menu label ^Live persistence (686-pae)
menu default
linux /live/vmlinuz
initrd /live/initrd.img
append boot=live noconfig=sudo username=root hostname=android-53f31a089339194f persistence

After that you need to rename isolinux.cfg to extlinux.conf and install extlinux:

$ cp /mnt/kali/isolinux/isolinux.cfg /mnt/kali/isolinux/extlinux.conf
$ extlinux --install /mnt/kali/isolinux/
/mnt/kali/isolinux/ is device /dev/sda1

Mount persistence partition and create config:

$ mkdir /mnt/persist
$ mount /dev/sda2 /mnt/persist/
$ echo "/ union" > /mnt/persist/persistence.conf

After that you can reboot and check, that persistent partition work.

Near year ago i configured zoneminder for monitoring my approach. But i got one problem, host that running zoneminder placed in same approach, so, if it will be stolen, it will be stolen with recordings. I spend a lot of time while choosing solution to organize replication on remote server. Most solution that i found work in “packet” mode, they start replication once in NN sec or after accumulating a certain number of events and usually use rsync. Rsync allow to reduce traffic usage, but increase time between event when new frame will be wrote on disk and event when frame will be wrote on remote side. In this situation every second counts, so I thought that solutions like “unison”, “inosync”, “csync2”, “lsyncd” not applicable.

I tried to use drbd, but get few problems. First – i do not have separate partition on host and can not shrink existing partitions to get new. I tried it with loopback devices, but drbd have deadlock bug when used with loopback. This solution work near two days after deadlock occurs, you can not read content of mounted fs or unmount it and only one solution to fix it that i found – reboot. Second problem – “split brain” situation, when master host restart. I did not spent time to found solution because all ready had first problem. May be it can be fixed with split-brain handlers script or with “heartbeat”. Drbd has great write speed in asynchronous mode and has small overhead, so, may be in another situation i will choose drbd.

Next what i tried was “glusterfs”, first i tried glusterfs 3.0. It was easily to configure it, and glusterfs was worked, but very slow. For good performance glusterfs need short latency between hosts. It useful for local networks but completely useless for hosts connected over slow links. Also glusterfs 3.0 did not have asynchronous write like in drbd. I temporarily thrown searching for solutions, but after a while in release notes for glusterfs 3.2 i found that gluster got “geo-replication“. First i think that this it what i need and before has understood (see conclusion) how it work i started to configure it.

If you will have troubles with configuration, installation  here you can find manual.
For Debian, first that you need is to add backports repository on host with zonemnider and on hosts where you planned to replicate data:

$ echo 'deb http://backports.debian.org/debian-backports squeeze-backports \
main contrib non-free' >> /etc/apt/sources.list
$ apt-get update
$ apt-get install glusterfs-server

After that you must open ports for gluster on all hosts where you want to use it:

$ iptables -A INPUT -m tcp -p tcp --dport 24007:24047 -j ACCEPT 
$ iptables -A INPUT -m tcp -p tcp --dport 111 -j ACCEPT 
$ iptables -A INPUT -m udp -p udp --dport 111 -j ACCEPT 
$ iptables -A INPUT -m tcp -p tcp --dport 38465:38467 -j ACCEPT

If you do not planned to use glusterfs over NFS (as i) you can skip last rule.
After ports will opened, gluster installed and service running you need to add gluster peers. For example you run zoneminder on host “zhost” and want to replicate it on host “rhost” (do not forget add hosts in /etc/hosts on both sides).  Run “gluster” and add peer (here and below gluster commands must to be executed on master host, i.e. on zhost):

$ gluster
gluster> peer probe rhost

Let’s check it:

gluster> peer status
Number of Peers: 1
 
Hostname: rhost
Uuid: 5e95020c-9550-4c8c-bc73-c9a120a9e96e
State: Peer in Cluster (Connected)

Next  necessary to create volumes on both hosts, do not forget to create directories where gluster will save their files. For examples you planned to use “/var/spool/glusterfs”:

gluster> volume create zoneminder transport tcp zhost:/var/spool/glusterfs
Creation of volume zoneminder has been successful. Please start the volume to access data.
gluster> volume create zoneminder_rep transport tcp rhost:/var/spool/glusterfs
Creation of volume zoneminder_rep has been successful. Please start the volume to access data.
gluster> volume start zoneminder
Starting volume zoneminder has been successfu
gluster> volume start zoneminder_rep
Starting volume zoneminder_rep has been successfu

After that you must configure geo-replication:

gluster> volume geo-replication zoneminder gluster://rhost:zoneminder_rep start
Starting geo-replication session between zoneminder & gluster://rhost:zoneminder_rep has been successful

And check that it is work:

gluster> volume geo-replication status
MASTER               SLAVE                                              STATUS    
--------------------------------------------------------------------------------
zoneminder           gluster://rhost:zoneminder_rep           starting...
gluster> volume geo-replication status
MASTER               SLAVE                                              STATUS    
--------------------------------------------------------------------------------
zoneminder           gluster://rhost:zoneminder_rep           OK

Also i made next configurations:

gluster> volume geo-replication zoneminder gluster://192.168.107.120:zoneminder_rep  config sync-jobs 4
geo-replication config updated successfully
gluster> volume geo-replication zoneminder gluster://192.168.107.120:zoneminder_rep  config timeout 120
geo-replication config updated successfully
gluster> volume set zoneminder nfs.disable on
Set volume successful
gluster> volume set zoneminder_rep nfs.disable on
Set volume successful
gluster> volume set zoneminder nfs.export-volumes off
Set volume successful
gluster> volume set zoneminder_rep nfs.export-volumes off
Set volume successful
gluster> volume set zoneminder performance.stat-prefetch off
Set volume successful
gluster> volume set zoneminder_rep performance.stat-prefetch off
Set volume successful

I disabled nfs because i did not planned to use gluster volumes over nfs, also i disabled prefetch because they produce next error on geo-ip modules:

E [stat-prefetch.c:695:sp_remove_caches_from_all_fds_opened] (-->/usr/lib/glusterfs/3.2.7/xlator/mount/fuse.so(fuse_setattr_resume+0x1b0) [0x7f2006ba8ed0] (-->/usr/lib/glusterfs/3.2.7/xlator/debug/io-stats.so
(io_stats_setattr+0x14f) [0x7f200467db8f] (-->/usr/lib/glusterfs/3.2.7/xlator/performance/stat-prefetch.so(sp_setattr+0x7c) [0x7f200489c99c]))) 0-zoneminder_rep-stat-prefetch: invalid argument: inode

In conclusion i must to say, that it is not a solution that i looked for, because as it turned out  gluster use rsync for geo-replication. Pros of this solution: it is work and easy to setup. Cons it is use rsync. Also i expected that debian squeeze can not mount gluster volumes in boot sequence, i tried to modify /etc/init.d/mountnfs.sh but without result, so i just add mount command in zoneminder start script.

PS
echo ‘cyclope:zoneminder      /var/cache/zoneminder   glusterfs       defaults        0       0’ >> /etc/fstab
And add ‘mount /var/cache/zoneminder’ in start section of /etc/init.d/zoneminder

PPS
Do not forget to stope zoneminder and copy content of /var/cache/zoneminder on new partition before using it.