Rsync of ZFS data with a FreeBSD live system

Booting into FreeBSD
Booting into FreeBSD

Let’s assume you rendered your FreeBSD system unbootable.. Yeah, happens to the best, but how can you still copy the data stored on a ZFS to another machine? You probably just shouted RSYNC - but it’s not that easy.

You would need a FreeBSD live os (either on a USB pen drive or on a CD/DVD) and boot into that system. However, by default you do not have network, the ZPool is not mounted, there is no rsync and SSH is not running, and the live os is not writable, which brings another few issues…

This is a step-by-step how-to through all the obstacles. Just boot into your live os (get it from and go on with the following…

Get Networking

By default your live system does not have networking setup correctly. Call ifconfig to see if the network interface is up. If it’s not you can bring it up using:

ifconfig em0 up

(assuming your inteface is called em0)

If it is up, you need to configure it. When you’re using a DHCP server you can just ask for an IP address using:

dhclient em0

Otherwise you need to configure the addresses manually:

ifconfig em0 inet netmask

Afterwards you should be able to ping other machines, such as


Mount the ZPool

Your ZPool won’t be mounted by default; you need to do it manually. To list all pools available on that machine just call:

zpool import

This searches through the devices in /dev to discover ZPools. You may specify a different directory with -d (see man page for zpool). To actually import and mount your ZPool you need to provide its name, for example:

zpool import -f -o altroot=/mnt zroot

This will import the ZPool zroot. Moreover, the argument -o altroot=/mnt will mount it to /mnt instead of / and the -f will mount it even if it may be in use by another system (here we’re sure it isn’t, aren’t we?).

Create some Writeable Directories

The next problem is, that you do not have permissions to write to /etc, which you need to e.g. create SSH host keys etc. However, that’s also not a big issue as we have the unionfs filesystem! :)

UnionFS will mount a directory as an overlay over another directory. Let’s assume you have some space in $SPACE (maybe in the ZPool that you just mounted or on another USB drive), then you can just create a few directories:

mkdir $SPACE/{etc,var,usr,tmp}

and mount it as unionfs to the root’s equivalents:

mount_unionfs $SPACE/etc /etc
mount_unionfs $SPACE/var /var
mount_unionfs $SPACE/usr /usr
mount_unionfs $SPACE/tmp /tmp

Now we can write to /etc, while the actual changes will be written to $SPACE/etc! Isn’t that a great invention?

Start the SSH service

Now that /etc is writable we can start caring about the SSH daemon. First, we need to configure it to allow root to login. Add the follwing line to the /etc/ssh/sshd_config:

PermitRootLogin yes

Then, we can start the ssh daemon using:

service sshd onestart

It will automatically create host keys and all the necessary things for a first start of SSH. If that was successful, port 22 should now be open:

# sockstat -4 -l
root     sshd       938   4  tcp4   *:22                  *:*
root     syslogd    542   7  udp4   *:514                 *:*

Set root Password

To be able to login you of course need to set a root password:

passwd root

Aftwerwards, you should be able to login through SSH from any other machine. Go ahaed and give it a try!

Install and Run rsync

Almost there, but the freeBSD live image doesn’t come with rsync installed. So we need to do it manually:

pkg install rsync

This will first tell us that not even pkg is installed, but answering the question with y it will automatically install itself. And as everything is mounted as UnionFS, the stuff will actually be installed to $SPACE/... instead of /. However, you should now be able to do the rsync job from where ever you want :)

Sector 32 is already in use by the program `FlexNet'

Just tried to install Grub on a debootstrap‘ed hard drive, but Grub complained:

Installing for i386-pc platform.
grub-install: warning: Sector 32 is already in use by the program 'FlexNet'; avoiding it.  This software may cause boot or other problems in future.  Please ask its authors not to store data in the boot track.
DRM is bugging us
DRM is bugging us! Image by Brendan Mruk and Matt Lee, shared under CC BY-SA 3.0

Never heard of that FlexNet thing, but according to Wikipedia it’s a software license manager. And we all know how this whole DRM thing just bugs us.. So it bugged me because the new system wouldn’t boot properly.. Other people having similar problems.

However, it seems impossible to force grub overriding this sector, but you may wipe it manually. In my case sector 32 was infected by DRM, so I did the following:

dd if=/dev/zero of=/dev/sda bs=512 count=1 seek=32

If that’s done Grub installs like a charm, the system booted again, and the admin was happy that another DRM thing died :)

The figure I used in this article was made by Brendan Mruk and Matt Lee. They share it as CC BY-SA 3.0.

Handy Docker Tools

Handy Docker Tools
Docker Tools

As I’m working with Docker quite intensively it was about time to develop some tools that help me managing different tasks. Some of them have already been existing as functions in my environment or something, but now they are assembled in a git repository at GitHub.

The toolbox currently consists of the following tools:.

dclean cleans your setup

The Docker-Clean tool dclean helps getting rid of old, exited Docker containers. Sometimes I forget the --rm flag during tests, and when I realise it there are already hundreds of orhpaned containers hanging around.. Running dclean without arguments removes all of them quickly.

Additionally, the dclean tool accepts a -i flag which will clean the images. It will prune all dangling images. Dangling images are orphaned and usually not needed anymore. Thus, dclean -i will remove them.

denter gets you into a containers

The Docker-Enter tool denter beames you into a running Docker container. Just provide the container’s name or CID as an argument to get a /bin/bash inside the container. Internally, denter will just call

docker exec -it "$NAME" "$EXEC"

with $EXEC being /bin/bash by default. So there is no magic, it’s just a shortcut.. You may overwrite the program to be executed by providing it as a second argument. That means,

denter SOMEID ps -ef

will execute ps -ef in the container with the id SOMEID.

dip shows IP addresses

The Docker-IP tool dip shows the IP addresses of running containers. Without arguments it will print the IP addresses, names, and container ids of all running containers. If your interested in the IP address of a specific container you may pass that container’s CID as an argument with -c, just like:

dip -c SOMEID

This will show the IP of the container with id SOMEID.

dkill stops all running containers

The Docker-Kill tool dkill is able to kill all running containers. It doesn’t care what’s in the container, it will just iterate over the docker ps list to stop all running containers.

As this is quite dangerous, it requires a -f flag to actually kill the containers. You may afterwards run the dclean tool from above to get rid of the cadavers..

dupdate updates images

The Docker-Update tool dupdate helps you staying up-to-date. It will iterate over all your images and tries to pull new versions of that image from the Docker registry (or your own registry, if you have one). By default, it will echo the images that have been updates and tells you which images cannot be found (anymore) on the registry. You may pass the -v to dupdate to enable verbose mode and also get a report for images that do not have a newer version at the registry. This way, you can make sure that all images are checked. Similarly, you can pass -s to enable silent mode and suppress messages about images that cannot be found at the registry.

You may also want to look at the Docker-Update tool?


Installing the tools is very easy: Just clone the Docker-Tools git repository at GitHub. If you’re using a Debian based system you may also install the tools through my apt-repository:

aptitude install bf-docker-tools

This way, you’ll stay up-to-date with bug fixes etc.

Firefox: Mute Media

Silence Firefox
Silence Firefox

You middle-click a few youtube videos and all start shouting against each other. You enter a website and it immediately slaps sound in you face. How annoying…

But there may be help.

Enter about:config and set

  • media.block-play-until-visible to true to only play media that is also in the current tab an do not play the stuff from the background
  • media.autoplay.enabled to false to stop autoplaying of some of the media (doens’t work everywhere, not sure why..)
  • dom.audiochannel.mutedByDefault sets the audio muted by default – essential for offices
  • plugins.click_to_play requires a click to run plugins, such as flash (which you are anyway not using!)

Fix highlight colors for QT apps on a GTK desktop

Okular: highlighted text is hardly readable
Okular: highlighted text is hardly readable

I’m using the i3 window manger. As smart as possible, increases productivity, and feels clean. Exactly how I like my desktop. I’m still very happy that Uschy hinted me towards i3!

However, I’m experiencing a problem with highlighted text in Okular, my preferred PDF viewer. When I highlight something in Okular the highlight-color (blue) is far too dark, the highlighted text isn’t readable anymore. I used to live with that, but it was quite annoying. Especially when you’re in a meeting/presentation and you want to highlight something at the projector. I just saw that problem occurring in Okular. Not sure why, but I honestly do not understand this whole desktop config thing – probably one of the reasons why I love i3 ;-)

Today, I eventually digged into the issue and found out what’s the problem how to solve the problem. Apparently, Okular uses a Qt configuration, that can be modified using the qtconfig tool. Just install it (here for Qt4 applications):

Configure the highlight color using the qtconfig tool
Configure the highlight color using the qtconfig tool
aptitude install qt4-qtconfig

When you run qt4-qtconfig a window will pop up, as you can see in the figure on the right:

  1. Select a GUI Style that is not Desktop Settings (Default), e.g. Cleanlooks.
  2. Then you can click the Tune Palette… button in the Build Palette section.
  3. A second window will pop up. Select Highlight in the Central color roles section.
  4. Finally you’re good to select the hightlight color using the color chooser button! :)
Okular highlighting text with fixed colors
Okular highlighting text with fixed colors

Was a bit difficult to find, but the result is worth it! The figure on the bottom shows the new highlight color – much better.

I will probably never understand all these KDE, QT, Gnome, GTK, blah settings. Every environment does it differently and changes the configuration format and location like every few months. At least for me that’s quite frustrating…

Martin Scharm

stuff. just for the records.

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