Home - The Movie

"In 200.000 years on Earth, humanity has upset the balance of the planet, estabilished by nearly four billion years of evolution. The price to pay is high, but it's too late to be a pessimist: humanity has barely ten years to reverse the trend, become aware of the full extent of its spoliation of the Earth's riches and change its patterns of consumption.

By bringing us unique footage from over fifty countries, all seen from the air, by sharing with us his wonder and his concern, with this film Yann Arthus-Bertrand lays a foundation stone for the edifice that, together, we must rebuild."

The movie features beautiful cinematography. If for no other reason, then watch it just because it's a masterpiece in showing off the beauties of Earth. Smile

How to use the VPN of a Windows virtual machine on the Ubuntu host via VirtualBox

Let's assume that you cannot make a VPN connection work on your Ubuntu host OS, but you can do it in a Windows guest VM. However you'd like to keep working on your host OS. If you've an SSH server on the other side of the VPN tunnel, then you're lucky, because setting up two port-forwardings is all you need.

How to copy a file from a specified offset efficiently

The answer is simple if you know "dd" well. I didn't (know about the skip_bytes and count_bytes iflag options).

Captive portal detection vs. automatic WiFi connection on Android (Lollipop and later)

Since Lollipop (5.1+) you might not be able to connect (or reconnect) to all authenticated (aka. password protected) WiFi networks. The culprit is called "captive portal detection". This feature is intended to help you use public (hotels, airports, etc.) WiFi access points by automatically detecting, when a router redirects all traffic to it's own so called "captive portal", where you can register your device for internet access.

How to Encrypt and Decrypt Files and Directories Using Tar and OpenSSL

To package, compress and encrypt:
tar cz path_to_source | openssl enc -e -aes256 -out encrypted.tar.gz

To decrypt, decompress and extract
openssl enc -d -aes256 -in encrypted.tar.gz | tar xz

How to binary compare the contents of two directories on Linux (recursively)

Run the following in both directories (change the output filename for the second):
find . -print0 | LC_ALL=C sort -z | xargs -0r md5sum > ../dir1.md5 2>&1

Compare the two resulting text files with eg. diff.
If you're interested only in files (and don't care for potential empty directories), then add -type f to the arguments of find.

All sorts of free "programming" fonts with an online test app

"The most complete resource for monospace fonts on the web." - and it sure is. Smile

How to fix tcpdump error with file permission denied

The referenced page describes that a potential reason for a "permission denied" message while trying to run tcpdump can come from Ubuntu's apparmor profiles. The syslog will contain something like this (if you run tcpdump with the "-r" switch to read from a packet capture dump):
Jan 15 14:09:21 somehost kernel: [877965.617109] type=1400 audit(1452863361.199:133): apparmor="DENIED" operation="open" profile="/usr/sbin/tcpdump" name="/home/someuser/capture-21980_2016-01-14T15-37-01.dump" pid=9724 comm="tcpdump" requested_mask="r" denied_mask="r" fsuid=1000 ouid=1000

You can check the apparmor profile here: /etc/apparmor.d/usr.sbin.tcpdump
The reason for the above error message was the filename ... the apparmor profile grants read permission only on files with the ".pcap" extension. Simply renaming the file solved my problem. However if you really have to work around something in the profile, you can add your own rules to /etc/apparmor.d/local/usr.sbin.tcpdump which is included in the main profile at the end (thus you can override everything that was set in the main profile).

How to mount HFS+ drive and ignore permissions

bindfs is the answer. It will take an already mounted file system and provide a view of it with whichever uid you'd like:

sudo apt-get install bindfs
mkdir ~/myUIDdiskFoo
sudo bindfs -u $(id -u) -g $(id -g) /media/diskFoo ~/myUIDdiskFoo

The same answer is available on this Superuser post too. Of course the "/media/diskFoo" path represents the mount point of the already mounted HFS volume.

External storage permissions in Android (up to KitKat, i.e. 4.4)

A very nice post on how the external storage permission system evolved, where did it get in KitKat and how it is implemented. For the changes in Lollipop read this: http://developer.android.com/about/versions/android-5.0.html#Storage

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