Arduino development with Eclipse

      No Comments on Arduino development with Eclipse

The Arduino IDE is great for beginners: It makes it really easy to write simple programs without having to care about compiler options, include paths, language standards or how to actually flash firmware onto the microcontroller. It even comes with a built-in serial monitor which can be a great tool for debugging.
Inevitably, as people dive deeper into the world of microcontrollers and the Arduino platform specifically, they usually want more control of the toolchain and use features like referencing source code across different projects and include external libraries. While that’s technically all possible with the Arduino IDE, some of the things might be a bit clunky to set up. IDEs like Eclipse are much more suited for these use cases.

Continue reading

Updating BIOS firmware via iPXE

      No Comments on Updating BIOS firmware via iPXE

These days mainboards usually come with some sort of wizbang tool that allow the user to update the BIOS from a USB drive or straight via network. Except, of course, that one single mainboard that absolutely needs a new BIOS version on a late Friday afternoon. And obviously the manufacturer only provides a flash tool for DOS and the mainboard is not supported by flashrom yet.
In those cases booting FreeDOS can be really handy. Booting FreeDOS via PXE is not that hard and it can also be booted via iPXE quite easily. If you do boot it via PXE, the easiest way to access the mainboard manufacturer’s flash tool and the new BIOS firmware from within FreeDOS is probably to include it in the PXE image file (see here). With iPXE however there’s a much more elegant way…

Continue reading

Migrating a virtual machine from KVM to ESXi

      No Comments on Migrating a virtual machine from KVM to ESXi

Migrating a virtual machine from one host to another is usually no big deal if both hosts run the same VMM. But what if one wants to move a VM from a host running a different hypervisor than the target host? In the case of moving a VM from KVM to ESXi that’s just not (easily) possible. However, one can convert the virtual hard drive and recreate the virtual machine on the target host, which should be good enough for most use cases.

Continue reading

OpenSSH cipher performance

      No Comments on OpenSSH cipher performance

The achievable speed of copying a file with OpenSSH (e.g. with scp) will depend on quite a few different factors such as CPU speed, CPU architecture, Network throughput, OpenSSH implementation, OS, hard drive speed, etc. But how much of a difference does choosing a different cipher algorithm make? And what’s the fastest OpenSSH cipher algorithm?

Turns out, there’s no simple answer to this question, since most of the factors that influence the transfer speed can be ruled out, but the results will at least depend on the hardware platform and OpenSSH version. There’s quite a few different benchmarks out there, e.g. for the Bifferbord, E5 xeon CPUs or different consumer grade CPUs and ARM processors. But since the results are so heavily platform dependent, it’s a good idea to run your own benchmark on the particular platform you are interested in. So here’s another data point for an Intel Xeon E5-2640 and OpenSSH 6.9p1 (OpenSSL 1.0.1k).

The test setup is quite similar to the one described at The bash script used to produce the data is:

for cipher in aes128-ctr aes192-ctr aes256-ctr arcfour256 arcfour128 aes128-cbc 3des-cbc blowfish-cbc cast128-cbc aes192-cbc aes256-cbc arcfour
   echo "$cipher"
   for try in 1 2
      scp -c "$cipher" /tank/fs/testfile.img root@localhost:/tank2/fs/

The test file consists of 5GiB random data. Both the source and target file system are RAM backed to remove the influence of HDD read and write speeds. In addition to that, the test file is written to localhost to ensure that network speed, load and NIC drivers do not influence the test results.

SCP file transfer speed

The results clearly show, that the Xeon’s AES instruction set is used. Most modern x86 CPUs do come with this extension these days.

While this data clearly suggests, that AES encryption is the faster cipher OpenSSH cipher (if there is hardware support for it as in this case), copying large amounts of data with scp is not a particularly interesting use case. Sending big streams of data through a pipe into ssh, as you do when you send and receive ZFS snapshots over ssh, is a very common application. For benchmarking reasons, sending actual ZFS snapshots is not ideal, since ZFS takes some extra time to check the receiving file system (and its snapshots) before starting the sending process. So here’s an altered script that should tell us, what the fastest cipher for that particular use case is:

for cipher in aes128-ctr aes192-ctr aes256-ctr arcfour256 arcfour128 aes128-cbc 3des-cbc blowfish-cbc cast128-cbc aes192-cbc aes256-cbc arcfour
   echo "$cipher"
   for try in 1 2
      cat /tank/fs/testfile.img | pv | ssh -c "$cipher" root@localhost "cat - > /dev/null"

The only difference can be found in the highlighted line: Instead of using scp the file is now piped directly into ssh and discarded on the receiving side. Again, the 5GiB test file lives on a RAM backed file system and the transfer is done to localhost.

SSH piped file transfer speed

Netbeans’ tomcat log file path

      No Comments on Netbeans’ tomcat log file path

Spawning a tomcat server instance from within Netbeans is really handy for rapid Java Servlet or JavaServer Pages application development. Since log levels are usually quite verbose during development, logs tend to pile up. So you might want to clean out the log directory from time to time. Or maybe you just want to go through one of those logs one more time with a proper editor.
Here’s Nebeans’ default tomcat log file storage location:


So for a current Netbeans with a recent tomcat version this could be something like ~/.netbeans/8.1/apache-tomcat-

Creating a zfs pool on RAM backed block devices

Especially for performance benchmarks it can be quite handy to have a zfs pool that’s not limited by the speed of the underlying hard drives or other block devices (like iSCSI or fibre channel). The Linux kernel has a nice block device driver that let’s you create virtual block devices that are RAM backed. To list the available options, use modinfo

# modinfo brd
parm:           rd_nr:Maximum number of brd devices (int)
parm:           rd_size:Size of each RAM disk in kbytes. (int)
parm:           max_part:Num Minors to reserve between devices (int)

To create three virtual block devices with a size of 2GiB each for example, load the brd module with the following options

# modprobe brd rd_nr=3 rd_size=2097152

which will create three devices named /dev/ramN:

# ls -lah /dev/ram*
brw-rw---- 1 root disk 1, 0 Apr 30 00:34 /dev/ram0
brw-rw---- 1 root disk 1, 1 Apr 30 00:34 /dev/ram1
brw-rw---- 1 root disk 1, 2 Apr 30 00:34 /dev/ram2

Note that the default value for the rd_nr parameter is 16, which would result in 16 /dev/ramN devices being created. However, the memory is still available until those virtual block devices are actually used.

Creating a zfs pool on these RAM backed block devices works just as with any other block device:

# zpool create tank ram0 ram1 ram2
# zpool status
  pool: tank
 state: ONLINE
  scan: none requested

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          ram0      ONLINE       0     0     0
          ram1      ONLINE       0     0     0
          ram2      ONLINE       0     0     0

errors: No known data errors

# zpool list
tank  5,95G   224K  5,95G         -     0%     0%  1.00x  ONLINE  -

Reading from and writing to a filesystem on this RAM backed pool should be quite fast

# zfs create tank/fs
# dd if=/dev/zero of=/tank/fs/testfile.img bs=1M count=5k
5120+0 records in
5120+0 records out
5368709120 bytes (5,4 GB) copied, 2,51519 s, 2,1 GB/s

Since the actual performance (throughput as well as IOPS) is heavily depending on the actual hardware, your mileage may vary here, of course. Please also keep in mind that writing zeros to a file with dd is a quick and easy way to get a first ballpark number, it is not a proper performance benchmark however. You might want to have a look at bonnie++ et al. for that.

Change keyboard configuration in console

      No Comments on Change keyboard configuration in console

To temporarily change a console’s keyboard mapping there’s loadkeys, a little user space program that allows you to alter the kernel’s keyboard mapping.
Loading the very handy US International keyboard layout, use

# loadkeys us-intl

To list the currently used keyboard layout or all available keyboard layouts, localectl can be used

# localectl status
   System Locale: LANG=en_US.UTF-8
       VC Keymap: us-altgr-intl
      X11 Layout: us
# localectl list-keymaps

If localectl is not available, keyboard mapping files are usually found at /lib/kbd/keymaps/xkb/ (e.g. Fedora) or /usr/share/kbd/keymaps/ (e.g. Arch Linux).

To permanently change the default keyboard layout system-wide, alter /etc/vconsole accordingly


Convert a JAR file into a Linux executable

      No Comments on Convert a JAR file into a Linux executable

With Java programs it’s quite common to combine several classes into one JAR archive. Java libraries are typically distributed this way as well.
On Linux platforms, people are quite used to using command line programs, but sometimes it’s handy to distribute a java program as an executable file that can be run by a simple double-click instead of opening a terminal and typing java -jar FancyProgram.jar. Of course, one could always configure the desktop environment to associate JAR files with the corresponding executable from the Java Runtime Environment, but adding the JAR archive as a payload to a common shell script is much more universal.

Here’s a small stub of code that will launch the Java interpreter (i.e. the binary called java) with itself as the JAR file to run.

MYSELF=`which "$0" 2>/dev/null`
[ $? -gt 0 -a -f "$0" ] && MYSELF="./$0"
if test -n "$JAVA_HOME"; then
exec "$java" $java_args -jar $MYSELF "$@"
exit 1

To add the original JAR archive as payload and make the resulting file executable, run

cat FancyProgram.jar > FancyProgram && chmod +x FancyProgram

You can now execute the resulting file with ./FancyProgram.

Binary payloads in shell scripts also allow you do distribute entire software packages that could easily consist of hundreds of files as a single shell script, as described in a great article from To wrap JAR archives in native Windows executables, have a look at


Command-line deploy vCenter appliance (VCSA) 6.0 on a Linux machine

Up to version 5.5 a vCenter appliance was usually deployed by importing the corresponding ovf template that could be downloaded from the VMware website. That process changed with version 6.0 since there is no longer an ovf template. Instead, VMWare provides and ISO image that contains the necessary data and tools to deploy a vCenter appliance, even directly from the command line.

After downloading the ISO image file from the my vmware portal mount it, e.g. to /mnt

# mount -o loop /var/lib/libvirt/images/VMware-VCSA-all-6.0.0-3343019.iso /mnt/

The vcsa command line deployment tool can be found at vcsa-cli-installer/lin64/vcsa-deploy. Since the available options and arguments to this tool are tucked away in one of the many vCenter documentation pdfs, here’s the output of vcsa-deploy --help

$ vcsa-cli-installer/lin64/vcsa-deploy --help
usage: vcsa-deploy install [-h] [--template-help] [-v] [-t]
                           [--log-dir LOG_DIR] [--verify-only]
                           [--skip-ovftool-verification] [--no-esx-ssl-verify]
                           [--sso-ssl-thumbprint SSL-SHA1-THUMBPRINT]

Deploy vCSA to a remote host.

optional arguments:
  -h, --help            Show this help message and exit.

Other Arguments:
  --template-help       Print out the help for template settings.
  -v, --verbose         Debug information will be displayed in the console. If you set this parameter, you cannot set --terse.
  -t, --terse           Only warning and error information will be displayed in the console. If you set this paramter, you cannot set --verbose.
  --log-dir LOG_DIR     Directory for log and other output files.
  --verify-only         Perform only the basic template verification and OVF Tool parameter verification, but do not deploy the vCenter Server Appliance.
                        Deploy the vCenter Server Appliance directly through OVF Tool without performing parameter verification. Basic template verification will still be performed.
  --no-esx-ssl-verify   Skip the SSL verification for ESXi connections.
  --sso-ssl-thumbprint SSL-SHA1-THUMBPRINT
                        Validates server certificate against the supplied SHA1 thumbprint.
  --accept-eula         Accept the end-user license agreement. This argument is required to deploy the appliance.

Required Arguments:
  template              Path of a JSON file that describes the vCenter Server Appliance deployment procedure.

Use --template-help for a list of template settings.

The exit codes and their meanings are:
0: Command ran successfully.
1: Runtime error.
2: Validation error.

You can find sample json templates for the deployment in vcsa-cli-installer/templates/install/. The options should be quite self-explanatory and cover

  • Networking
  • SSO
  • System
  • Database
  • Deployment

A comprehensive list of valid parameters of the json file is available as well by invoking vcsa-cli-installer/lin64/vcsa-deploy --template -h

The deployment.option parameter specifies, how much virtual harware (CPUs, RAM) should be allocated for the vCenter appliance. Here’s a table of the available options (taken from the VMware vSphere 6.0 Documentation Center)

vCenter Server Appliance size

Optionmax. hostsmax. VMsappliance CPUsappliance Memory
tiny1010028 GB
small1001.000416 GB
medium4004.000824 GB
large1.00010.0001632 GB

Note that the hostname parameter in the network section needs to have a forward and reverse DNS entry (see VMware vCenter server 6 deployment guide) to work. An IP address is also fine though.

After editing the json file to reflect your configuration you can deploy the vCenter appliance by running vcsa-cli-installer/lin64/vcsa-deploy path_to_config_file.json --accept-eula

# vcsa-cli-installer/lin64/vcsa-deploy ~/vcenter.json --accept-eula
Performing basic template verification...
Starting vCenter Server Appliance installer to deploy
This appliance is a vCenter Server instance with an embedded Platform Services
See /tmp/vcsaCliInstaller-2016-03-08-15-06-xXUT2j/vcsa-cli-installer.log for the
installer logs.
Run the installer with "-v" or "--verbose" to log detailed information
Running OVF Tool to deploy the OVF...
Opening vCenter Server Appliance image: /mnt/vcsa/vmware-vcsa
Opening VI target: vi://root@esxihost:443/
Deploying to VI: vi://root@esxihost:443/

Progress: 99%
Transfer Completed
Powering on VM: vCenter-Server-Appliance

Progress: 98%
Power On completed.
Waiting for IP address...
Received IP address:

Installing services...
vCSA firstboot: Progress: 5% Setting up storage
vCSA firstboot: Progress: 50% Installing RPMs
vCSA firstboot: Progress: 55% Installed
vCSA firstboot: Progress: 63% Installed rvc_1.4.0-3196809_x86_64.rpm
vCSA firstboot: Progress: 64% Installed
vCSA firstboot: Progress: 65% Installed
vCSA firstboot: Progress: 66% Installed
vCSA firstboot: Progress: 67% Installed
vCSA firstboot: Progress: 70% Installed
vCSA firstboot: Progress: 73% Installed
vCSA firstboot: Progress: 77% Installed
vCSA firstboot: Progress: 79% Installed
vCSA firstboot: Progress: 80% Installed VMware-invsvc-6.0.0-3242064.x86_64.rpm
vCSA firstboot: Progress: 81% Installed VMware-vpxd-6.0.0-3339084.x86_64.rpm
vCSA firstboot: Progress: 81% Installed
vCSA firstboot: Progress: 83% Installed
vCSA firstboot: Progress: 84% Installed
vCSA firstboot: Progress: 85% Installed ipxe-1.0.0-1.2882051.vmw.i686.rpm
vCSA firstboot: Progress: 86% Installed
vCSA firstboot: Progress: 86% Installed VMware-sps-6.0.0-3339084.x86_64.rpm
vCSA firstboot: Progress: 87% Installed VMware-vdcs-6.0.0-3242353.x86_64.rpm
vCSA firstboot: Progress: 89% Installed
vCSA firstboot: Progress: 90% Installed vmware-vsm-6.0.0-3339084.x86_64.rpm
vCSA firstboot: Progress: 90% Installed vsphere-client-6.0.0-3338001.noarch.rpm
vCSA firstboot: Progress: 91% Installed
vCSA firstboot: Progress: 95% Configuring the machine
Services installations succeeded.
Configuring services for first time use...
vCSA firstboot: Progress: 3% Starting VMware Authentication Framework...
vCSA firstboot: Progress: 10% Starting VMware Identity Management Service...
vCSA firstboot: Progress: 17% Starting VMware Component Manager...
vCSA firstboot: Progress: 20% Starting VMware License Service...
vCSA firstboot: Progress: 24% Starting VMware Platform Services Controller
vCSA firstboot: Progress: 27% Starting VMware Service Control Agent...
vCSA firstboot: Progress: 31% Starting VMware vAPI Endpoint...
vCSA firstboot: Progress: 34% Starting VMware System and Hardware Health
vCSA firstboot: Progress: 37% Starting VMware Appliance Management Service...
vCSA firstboot: Progress: 44% Starting VMware Common Logging Service...
vCSA firstboot: Progress: 48% Starting VMware Postgres...
vCSA firstboot: Progress: 55% Starting VMware Inventory Service...
vCSA firstboot: Progress: 58% Starting VMware Message Bus Configuration
vCSA firstboot: Progress: 63% Starting VMware vSphere Web Client...
vCSA firstboot: Progress: 64% Starting VMware vSphere Web Client...
vCSA firstboot: Progress: 65% Starting VMware vSphere Web Client...
vCSA firstboot: Progress: 68% Starting VMware ESX Agent Manager...
vCSA firstboot: Progress: 72% Starting VMware vSphere Auto Deploy Waiter...
vCSA firstboot: Progress: 75% Starting VMware vSphere Profile-Driven Storage
vCSA firstboot: Progress: 79% Starting VMware Content Library Service...
vCSA firstboot: Progress: 82% Starting VMware vCenter Workflow Manager...
vCSA firstboot: Progress: 89% Starting VMware vService Manager...
vCSA firstboot: Progress: 93% Starting VMware Performance Charts...
vCSA firstboot: Progress: 96% Starting vsphere-client-postinstall...
First time configuration succeeded.
vCenter Server Appliance installer finished deploying
This appliance is a vCenter Server instance with an embedded Platform Services
    System Name:
    Log in as: Administrator@vsphere.local
Finished successfully.

You should now be able to long into the vSphere Web Client with Administrator@vsphere.local as username and the password you specified in the json file

vSphere Web Client

You can safely ignore the warning about the browser-OS combination.

Tunneling browser traffic through an ssh jumpbox

It can be very handy sometimes to tunnel your browser’s traffic through a secure channel, for example when you are on an insecure or unknown network like a hotel, cafe or airport etc.

To open up a SOCKS proxy on port 8080, run

ssh -C2qTnN -D 8080

To configure Firefox to use the proxy go to Edit → Preferences → Advanced → Network → Settings and enable ‘Manual proxy configuration’

Edit → Preferences → Advanced → Network → Settings

Enable SOCKS proxy in Edit → Preferences → Advanced → Network → Settings

You can also tunnel Firefox’s DNS queries through the SOCKS proxy by enabling the ‘Remote DNS’ checkbox.

For chrome, you can use the settings dialog quite similar to the Firefox example above, but you can also specify the proxy through the command line with the SOCKS_SERVER environment variable. To spawn a new, temporary chrome session with the SOCKS proxy configured, run

SOCKS_SERVER=localhost:8080 google-chrome --user-data-dir=/tmp/chrome $1

Note that’s it’s a bit more tricky to tell chrome not to rely on local DNS queries. For details have a look at the chromium documentation.