Remove Color Channels from TIFF Using Command Line

5 08 2012

The R function


is used a lot to export R graphics e.g. for publication purposes. The tiff includes all 8 color channels and this collides with formatation requirements of most jounals (1200dpi but not more than some MB in size).

tiff("Whiskerplot.tiff" , width = 8.8 , height = 8.8 , units = "cm" , pointsize = 8 , res = 1200)
produces the required 1200 dpi resolution for monochrome plots, but with all 8 color channels (although just one is necessary) this results in 49.4MB for a tiny 8.8×8.8 cm (ca 3.5×3.5 inch) plot. I used GIMP to remove the color channels with

Image > Mode > Indexed > 1-bit monochrome

but this required opening GiMP, the file, the menu and saving. And again, when the plot had to be modified.

Since this has to be done for each and every publication figure I looked up a command line solution and here it is:
convert Whiskerplot.tiff -flatten -monochrome Whiskerplot_monochrome.tiff
removes all unnecessary colorchannels from Whiskerplot.tiff and saves it as Whiskerplot_monochrome.tiff, reducing the size from 49.4MB to 2.1MB while the result is exactly the same.

Hattip: Paddy Landau on ubuntuforums

Command line method to copy all files out of a folder tree

23 07 2012

This is not so much statistics, but I do want to keep this in case I need it again.

For years I am collecting pictures and photos in a host of folders. Most pictures are in Pictures with a lot of subfolders and a lot of duplicates. Just today I imported another chunk of pictures with gThumb which has the very nice feature of creating a Year/Month/Day/ folder tree and moves the files there. But: I chose the wrong parent folder, so that I have a lot of /Year/Month/Day/ folders in more than one place. Bummer. And: this might/will happen again.

What I wanted to do is get all picture files out of all folders and sort them in one folder by name. Then have a look at the list (takes time), remove duplicates and move them back into /home/rforge/Pictures/year/month folders (for this I use gThumb, to lazy to research the find way in command line — if somebody reads this he/she might comment on that).

find /path/to/Pictures -name="*.jpg" -exec cp '{}' '/path/to/temporary_jpg/' ';'

finds all .jpg files in the /path/to/Pictures folder and copies (cp) them to a folder temporary_jpg in the home folder (which has to exist before running find.

Since not all files are jpg (case sensitive), like e.g. jpeg, JPEG, BMG, tiff and so on (even .mpg videos are burried in this dreadful old “Pictures” folder/dump) one can omit the -name specification and just dump everything in a flat folder sort by extension/file type and clean up:

find /path/to/Pictures -exec cp '{}' '/path/to/temporaryPics' ';'

Helpful links, which I used:

Coding Tiger
(with comments)
and for renaming all the filename salad from dozens of cameras to a consistend format, that is Year-Month-day-hour-minute-second.jpg (which I do not cover here): ak4good on ubuntu Forum (comment #6).

Data Backup in the AWS Cloud with rsync

16 11 2011

After admitting that of all things Microsoft offers 25GB cloud storage for its Windows Live subscribers I will walk through my latest preliminary experiments regarding backup of important data using the using the Amazon Advanced Web Services. The storage is not free but quite cheap at around 0.1$ per GB and month.

If you use Windows and MS Office a lot use Skydrive and don’t read on 😉 There are posts which describe how to map the Skydrive like a local harddisk using MS Word.

On the long run I would like to mount a EBS storage like a local file tree, probably using WebDAV, but this is my first successful preliminary solution. s3cmd does not work for me.

Using Ubuntu/Linux rsync is a well established, reliable and easy to use tool to keep data between locations in sync. The following post marries rsync with an Elastic Cloud (EC2) server instance for an hour or some. One has to set up the so called rsync daemon and attach a persistent Elastic Block Storage.

This is another post. I will link to it later. There will also be a small script. There are some holes in this tutorial, only the direct configuration of the rsync daemon (including the script) is complete and working. I filled in some hints how to get to this stage. But will write follow ups on that.

System Out provided a nice tutorial of how to set up the rsync in demon mode on a server which listens for clients to sync their data.

Here is my version of it, with a short script at the end which should do the job.


Of course you need to have rsync on both machines (the server and the client); since both are Ubuntu this is the case.

I will write another post on how to start the server. It is completely possible and quite intuitive to achieve it in the Amazon web interface. When the server is running and an extra EBS harddisk is attached you have to connect to the server using ssh

Mount the persistent drive

There are some posts about the advantages of the xfs filesystem, so I sticked to it. Alestic recommends it for all persistent EC2 cloud disks and I trust they know what they are doing. But xfs is not per default included in the Ubuntu micro instance I use for my backups. That said, in the SSH shell:

sudo apt-get install -y xfsprogs
sudo modprobe xfs

If the backup volume is newly created then format it:
sudo mkfs.xfs /dev/xvdb
Note: Only the first time. Otherwise you wipe your data, of course. Note also the device name. I attached it as /dev/sdb. Though it showed up in the Ubuntu Oneiric i386 t1.micro instance as /dev/xvdb.

Now mount the volume
echo "/dev/xvdb /media/backup xfs noatime 0 0" | sudo tee -a /etc/fstab
sudo mkdir /media/backup
sudo mount /media/backup
sudo chown ubuntu:ubuntu /media/backup
sudo chmod 777 /media/backup

Configuration files

On the server machine you need to set up a daemon to run in the background and host the rsync services.

Before you start the daemon you need to create some rsync daemon configuration files in the /etc directory.

Three files are necessary:

  1. /etc/rsyncd.conf, the actual configuration file,
  2. /etc/rsyncd.motd, Message Of The Day file (the contents of this file will be displayed by the server when a client machine connects) and
  3. /etc/rsyncd.scrt, the username and password pairs.

To create the files on the server:
sudo nano /etc/rsyncd.conf

Now enter the following information into the rsyncd.conf file:

motd file = /etc/rsyncd.motd
path = /media/backup
comment = the path to the backup directory on the server
uid = ubuntu
gid = ubuntu
read only = false
auth users = ubuntu
secrets file = /etc/rsyncd.scrt

Hit Ctrl-o to save and Ctrl-x to close nano.

The uid, gid, auth users are the users on the server. In the ssh session on the ec2 instance the user is ubuntu.

The format for the /etc/rsync.scrt file is

Use nano to put some arbitrary text into the /etc/rsync.motd.

Now you should have all the configuration information necessary, all that’s left to do is open the rsync port and start the daemon.

To open the port, open the /etc/default/rsync file, i.e.,

sudo nano /etc/default/rsync

and set RSYNC_ENABLE=true.

Here you might also specify another port than the default 873. Remember to open the port in the security group. Either with the AWS web interface in your browser or in the shell using the ec2-api-tools:
ec2-authorize default -p 873

Now to start the daemon,
sudo /etc/init.d/rsync restart
and exit the SSH session.

Syncing a folder

Now you can use your local shell to push some folders or files to the server. Update the server side from the client machine with ec2-api-tools installed:
EXIP=`ec2din | grep INSTANCE | grep -v terminated |awk '{print $4}'`
rsync -auv /home/rforge/articles ubuntu@$EXIP::backup/

$EXIP would be the server ip address

This gets the IP of the server from the ec2-api-tool and passes it to RSYNC.

Otherwise you have to remember the IP of your instance from the web interface and substitut it for
rsync -auv /PATH/TO/FOLDER/ ubuntu@$

::backup has to match [backup] in the /etc/rsyncd.conf file. You will see the rsyncd.motd message and get prompted for the password in the rsyncd.scrt file. Then rsync starts the upload.

A Script

The following script should do the daemon setup after connecting to the server via ssh and mounting the volume. Keep me posted if something does not work.

echo "motd file = /etc/rsyncd.motd
path = /media/backup
comment = the path to the backup directory on the server
uid = ubuntu
gid = ubuntu
read only = false
auth users = ubuntu
secrets file = /etc/rsyncd.scrt" > rsyncd.conf
sudo mv rsyncd.conf /etc/
sudo echo "Greetings! Give me the right password! Me want's it!" > rsyncd.motd
sudo mv rsyncd.motd /etc/
sudo echo "ubuntu:YourSecretPassword" > rsyncd.scrt
sudo mv rsyncd.scrt /etc/
sudo chmod 640 /etc/rsyncd.*
sudo chown root:root /etc/rsyncd.*
## enable demon mode in the /etc/default/rsync file
sudo cat /etc/default/rsync | sed 's/RSYNC_ENABLE=false/RSYNC_ENABLE=true/g' > rsync
sudo mv rsync /etc/default/
sudo chown root:root /etc/default/rsync
sudo chmod 644 /etc/default/rsync
sudo /etc/init.d/rsync restart # start the demon

Find BIOS version in Ubuntu

4 10 2011

The dmidecode command line utility dumps a list of SMBIOS specifications to the standard output. In order to get the version number of the currently installed BIOS open a shell and
sudo dmidecode --type 0 | grep Revision

The –type 0 option restricts the output to BIOS specific information and grep fishes for the revision number.

On my X61s Thinkpad the resulting output is
BIOS Revision: 2.19
Firmware Revision: 1.3

BASH: Convert Uppercase to Lowercase letters

12 09 2011

Vivek Gite on nixCraft suggests tr to tranform uppercase letters in the textfile input.txt to lowercase and output the transformed text to output.txt.

tr '[:upper:]' '[:lower:]' output.txt

I needed to clean up a messy old scriptfile where I lost track of my variable naming convention.

Very useful indeed 🙂

Add public key behind a firewall in Ubuntu Shell

7 09 2011

In short: Use
sudo apt-key adv --keyserver hkp:// --recv-key E084DAB9
instead of
sudo apt-key adv --keyserver --recv-key E084DAB9
This way you force port 80 which is usually clear.

I got the idea from the answer of Phil Bradley on the forum. He claimed that this would be fixed in Natty, but it isn’t although the configuration file he mentions has the port80 specification added by default, apt-key does not use it. The above snippet solves that.

For those Ubuntu users who have no idea what I am talking about:

Installing the newest R-version in Ubuntu requires to append the CRAN repository to you /etc/apt/sources.list. One might hit Alt+F2 and enter
gksu gedit /etc/apt/sources.list

With Xubuntu you would use mousepad instead of gedit. In any distro you can use
sudo nano /etc/apt/sources.list
in a terminal.

Usually I add the line
deb natty/
at the end of the file and update with
sudo apt-get update.

CRAN at University of Bergen is closest to me. You might want another one (check the site for mirrors).

apt-get update answers with a warning
GPG error: nat/ Release: The folowing signatures coldn't be verified because the public key is not abailable

That is not a problem. One can install R and packages anyway, but it is better to have the public key.

Behind a firewall (and many public and open hotspots block several ports) it is not possible to use

sudo apt-key adv --keyserver --recv-key E084DAB9

since the port through which the keyserver is contacted is blocked on most firewalls. You have to force port 80 by:
sudo apt-key adv --keyserver hkp:// --recv-key E084DAB9

After the key is added
sudo apt-get update
sudo apt-get install R-recommended emacs ess

proceeds without warning nor error.

Sane PATH variable in Emacs on Mac OS X

16 08 2011

On Mac OS X the system PATH variable is not recognized by emacs. This means that one can not simply type


in the emacs shell to get into the database. The emacs shell complains about “binary not found”.


echo $PATH

reveals that emacs just looks into /bin, /usr/bin, /sbin and /usr/sbin.

To set the $PATH variable inside emacs one can append the following lines to the .emacs file (found on github, hattip Alex Payne):

; sane path
(setq path "/bin:/usr/bin:/sbin:/usr/sbin:/usr/local/bin:/usr/local/mysql/bin")
(setenv "PATH" path)

Next time Emacs starts one can go to the shell and


presents the database prompt.