CONTINUAL INTEGRATION

Problem scenario
You want to use the strace command. How do you use it?

Solution

1. Go to a Linux command prompt.
2. Run this: sleep 100 &
3. Look at the number the above command produced (e.g., 310222). Craft a command like this (but replace 310222 with the number in the above command): strace kill 310222
4. Run the command drafted above. You should see lines like "openat…" and "kill". In the kill command you will see the returned signal from the kernel (e.g., SIGTERM)
5. Run this: sleep 100 &
6. Look at the number the above command produced (e.g., 310222). Craft a command like this (but replace 310222 with the number in the above command): strace kill -9 310222
7. Run the command drafted above. You should see lines like "openat…" and "kill". In the kill command you will see the returned signal from the kernel (e.g., SIGKILL)

FFR
The -9 flag in kill will kill a process; normally kill would just terminate the process.

To learn more about strace, see this external posting.

Problem scenario
You do not want to use pip or pip3 to install opencv. How do you install opencv (with the -DWITH_FFMPEG=ON flag)?

Solution
Prerequisite
This assumes that cmake has been installed. If you are running Ubuntu/Debian, run this: sudo apt -y install cmake
If you are running CentOS/RHEL/Fedora (some RedHat derivative), run this: sudo yum -y install cmake
If you are running SUSE, run this: sudo zypper -n install cmake

Procedures

Run these commands:

wget -O opencv.zip https://github.com/opencv/opencv/archive/master.zip

sudo cp -i opencv.zip /bin/
cd /bin
sudo unzip /bin/opencv.zip
sudo mkdir build && cd build
sudo cmake ../opencv-master -DWITH_FFMPEG=ON

Problem scenario
You want to use a virtual environment to install pip packages. You want to run a Python program with a module that will require a pip installation. What should you do to install and configure the environment and then enter it using Ubuntu/Debian Linux?

Solution

sudo apt -y install python3-virtualenv
sudo apt -y install python3.*-venv
python3 -m venv cont_int #replace "cont_int" with the name of the directory you want to create
cd cont_int
source bin/activate

Problem scenario
You have a Windows laptop with a DVD player. You want to boot to a Linux hard drive from time-to-time. But you do not want to dual boot the same hard drive (where one hard drive supports two different bootable OSes). What should you do?

Solution
You should purchase a hard drive adapter (aka a caddy) made to interface with the internal DVD player connection. You will lose space for your DVD player if you do this (and have one fewer DVD drives). But if you have a second hard drive, it can go where the DVD player is. (If you change your mind later and want to go back to having a DVD player, you can do that.)

Problem scenario
You want Google maps to rotate rectangularly when you use your Android device as a GPS in your car. You want to view the map so the width of the screen and height change 90 degrees based on the way you hold the phone (so it responds to gravity). How do you get the screen to adjust to have a layout that is appropriate for holding the smart phone sideways?

Solution
Go to the top of the screen and swipe downwards.
Click the "Portrait" icon.

(It should change to auto rotate). That's it.