Before starting, I have to mention this tutorial is not about ZFS Fuse which comes by default with Debian. This is the real deal, the native ZFS for Linux, without fuse support. In theory should be faster and more reliable and according to my tests so far, it is amazing!

First of all, install ZFS:

UPDATE: ZFS packages are included in debian repository. So all you have to do now is:

apt update
apt install dpkg-dev linux-headers-$(uname -r) linux-image-amd64

For that you will have to stop the machines one by one and configure in VirtualBox the serial port. In this example we will use a virtual serial port configured trough a pipe on the host machine.

Candy (node 1) VirtualBox Serial Port Configuration:

Enable Serial Port check box: checked (enabled)
Port Number: COM1
Port Mode: Host Pipe
Create Pipe check box: checked (enabled)
Port/File Path: /tmp/vboxDONOTDELETES0

The moment you start candy, you should see the pipe file in core (host machine) created:

Here you can find some common commands related to DRBD. They will be added once I find use of them on my daily work. Stay tuned!

How to force re-sync by invalidating the data on the node you are in:

root@eave:~# [color=green]drbdadm invalidate nfs[/color]
root@eave:~# cat /proc/drbd 
version: 8.3.11 (api:88/proto:86-96)
srcversion: F937DCB2E5D83C6CCE4A6C9 
 0: cs:SyncTarget ro:Secondary/Primary ds:Inconsistent/UpToDate C r-----
    ns:0 nr:28860 dw:24380 dr:0 al:0 bm:2 lo:36 pe:434 ua:35 ap:0 ep:1 wo:f oos:26192512

STONITH is short for "Shoot The Other Node In The Head". It's a technique for fencing in computer clusters.

Fencing is the isolation of a failed node so that it does not cause disruption to a computer cluster. As its name suggests, STONITH fences failed nodes by resetting or powering down the failed node.

Multi-node error-prone contention in a cluster can have catastrophic results, such as if both nodes try writing to a shared storage resource. STONITH provides effective, if rather drastic, protection against these problems.

In this situation, ssh was unable to start because the wpar was restored from standalone machine backup (mksysb).
However, even if this is not your case, you can try to see if the procedure will fix your ssh.

SSH doesn't want to start:

gzaix@root:/home/root # lssrc -s sshd         
Subsystem         Group            PID          Status 
 sshd             ssh                           inoperative
gzaix@root:/home/root # startsrc -s sshd
0513-059 The sshd Subsystem has been started. Subsystem PID is 18415656.

You have upgraded to Yosemite and found this error while trying to upgrade macports via command line?

fmbp:~ root# port -v selfupdate
Error: Current platform "darwin 14" does not match expected platform "darwin 13"
Error: If you upgraded your OS, please follow the migration instructions: https://trac.macports.org/wiki/Migration
OS platform mismatch
    while executing
"mportinit ui_options global_options global_variations"
Error: /opt/local/bin/port: Failed to initialize MacPorts, OS platform mismatch

So you have configured a brand new iscsi disk and want to put it to use in linux client?
No problem, read below!

Note: in our example, the ISCSI server is on 192.168.69.66

1. Discover the disks:

venus:~# iscsiadm -m discovery -t sendtargets -p 192.168.69.66
192.168.69.66:3260,3 iqn.2014-07.ro.gz.sun:swap-venus

2. activate them:

How to fix bash on Debian Squeeze

Security researchers from Red Hat have uncovered a new exploit in the common "Bash" command shell found in OS X, Linux, AIX and many other *nix platforms which can be used to deploy malicious code with minimal effort. Due to the ubiquity of the Bash shell, the exploit can also affect a wide variety of different web-connected devices and properties, including unsecured websites, smart home appliances, servers, and more.

As mentioned above, this vulnerability is not limited to only one platform but in the same time in doesn't affect the average consumer because even if they have "bash" in their computers, they do not use it in a way that it can be vulnerable. Unless you are using your computer as a server that accepts commands from untrusted sources (like web servers for example) (and then only if it sets environment variables based on commands from untrusted sources) you do not have to worry about.