Wednesday, November 25, 2020

Install virtualenv

# Step 1: Update your repositories
sudo apt-get update
# Step 2: Install pip for Python 3
sudo apt-get install build-essential libssl-dev libffi-dev python-dev
sudo apt install python3-pip
# Step 3: Use pip to install virtualenv
sudo pip3 install virtualenv
# Step 4: Launch your Python 3 virtual environment, here the name of my virtual environment will be env3
virtualenv -p python3 env3
# Step 5: Activate your new Python 3 environment. There are two ways to do this
. env3/bin/activate # or source env3/bin/activate which does exactly the same thing
# you can make sure you are now working with Python 3
python -- version
# this command will show you what is going on: the python executable you are using is now located inside your virtualenv repository
which python
# Step 6: code your stuff
# Step 7: done? leave the virtual environment
deactivate

 

Friday, September 11, 2020

rsync with a non-standard port

 rsync -avz -e "ssh -p $portNumber" user@remoteip:/path/to/files/ /local/path/

Tuesday, September 1, 2020

Common cmd of ffmpeg

 Images -> video

    ffmpeg -r 30 -f image2 -s 1280x720 -start_number 1 -i %06d.png -vframes 1000 -vcodec libx264 -crf 25  -pix_fmt yuv420p out.mp4


Video -> frames with specifc frame index

 cmd = "ffmpeg -i {} -vf select='between(n\,{}\,{})' -vsync 0 -start_number {} {}/%06d.jpg".format(video_path, s, t, s, out_path)


Tuesday, August 4, 2020

Move an Apache Web Root Directory to a New Location on Ubuntu

How To Move an Apache Web Root Directory to a New Location on Ubuntu 

From https://www.digitalocean.com/community/tutorials/how-to-move-an-apache-web-root-to-a-new-location-on-ubuntu-16-04

Prerequisites

To complete this guide, you will need:

  • An Ubuntu 16.04 server with a non-root user with sudo privileges. You can learn more about how to set up a user with these privileges in our Initial Server Setup with Ubuntu 16.04 guide.

  • An Apache2 web server: If you haven’t already set one up, the Apache section of the in-depth article, How To Install Linux, Apache, MySQL, PHP (LAMP) stack on Ubuntu 16.04, can guide you.

  • A new location for your document root: The new document root location is completely configurable based on your needs. If you are moving your document root to a different storage device, you will want to select a location under the device’s mount point.

In this example, we will use the /mnt/volume-nyc1-01 directory. If you are using Block Storage on DigitalOcean, this guide will show you how to mount your drive before continuing with this tutorial.

Step 1 — Copying files to the new location

On a fresh installation of Apache, the document root is located at /var/www/html. If you’re working with an existing server, however, you may have a significantly different setup including multiple document roots in corresponding VirtualHost directives.

You can search for the location of additional document roots using grep. We’ll search in the /etc/apache2/sites-enabled directory to limit our focus to active sites. The -R flag ensures that grep will print both the DocumentRoot and the filename in its output:

  • grep -R "DocumentRoot" /etc/apache2/sites-enabled

The result will look something like the output below, although the names and number of results are likely to be different on an existing installation:

Output
sites-enabled/000-default.conf DocumentRoot /var/www/html

Use the feedback from grep to make sure you’re moving the files that you want to move and updating their appropriate configuration files.

Now that we’ve confirmed the location of our document root, we’ll copy the files to their new location with rsync. Using the -a flag preserves the permissions and other directory properties, while-v provides verbose output so you can follow the progress.

Note: Be sure there is no trailing slash on the directory, which may be added if you use tab completion. When there’s a trailing slash, rsync will dump the contents of the directory into the mount point instead of transferring it into a containing html directory:

  • sudo rsync -av /var/www/html /mnt/volume-nyc1-01

Now we’re ready to update the configuration.

Step 2 — Updating the configuration files

Apache2 makes use of both global and site specific configuration files. For background about the hierarchy of configuration files, take a look at How To Configure the Apache Web Server on an Ubuntu or Debian VPS.

If you’re working with an existing installation, you should modify the virtual host files you found earlier with the grep command. For our example, we’re going to look at the two Virtual Host files that ship with Apache by default, 000-default.conf and default-ssl.conf.

We’ll start by editing the 000-default.conffile:

  • sudo nano /etc/apache2/sites-enabled/000-default.conf

Next we’ll find the line that begins with DocumentRoot and update it with the new location.

Note: You should look for other places the original path showed up, and change those to the new location as well. With a default installation, there’s the DocumentRoot and a Directory block you’ll need to change. On an existing installation, you may find things like aliases and rewrites that need updating, too. Wherever you see the original document root’s path in the output of grep, you’ll need to investigate.

/etc/apache2/sites-enabled/000-default.conf
<VirtualHost *:80>
        ServerAdmin webmaster@localhost
       DocumentRoot /mnt/volume-nyc1-01/html
        <Directory />
                Options FollowSymLinks
                AllowOverride None
       </Directory>
      <Directory /mnt/volume-nyc1-01/html/>
                Options Indexes FollowSymLinks MultiViews
                AllowOverride None
                Require all granted
        </Directory>

Step 3 — Restarting Apache

Once you’ve finished the configuration changes, you can make sure the syntax is right with configtest:

  • sudo apachectl configtest

You will get feedback from apachectl configtest with a fresh install:

Output
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message Syntax OK

As long as you get Syntax OK, restart the web server. Otherwise, track down and fix the problems it reported.

Use the following command to restart Apache:

  • sudo systemctl reload apache2

Thursday, July 16, 2020

File read error when using multithreading (workers)

Detectoron2, pythorch 1.5
panda.read_csv() error
"
pandas.errors.ParserError: Error tokenizing data. C error: Calling read(nbytes) on source failed. Try engine='python'.
"

Need to use with to keep file is closed after reading.

Solution

with open(filename) as f:
  df = panda.read_csv(f)

Wednesday, May 20, 2020

Install cuda 10.2

1. Uninstall existing nvidia driver

nvidia-installer --uninstall

or

The correct way to uninstall just cuda and keep your nvidia drivers would be:
sudo apt purge "libcublas*" "cuda-*" cuda
Possible, because they were installed as requirements, you can also purge,
sudo apt purge "nsight-*" nvidia-modprobe
After that you can, if you want, also remove the nvidia drivers with:
sudo apt purge "*nvidia*"
Of course, if you installed cuda using nvidia's .run file then this won't work; in that case you probably have some uninstall script.

2. Close X server
# To stop:
sudo init 3
# To resume:
sudo init 5
3. Download & install
wget http://developer.download.nvidia.com/compute/cuda/10.2/Prod/local_installers/cuda_10.2.89_440.33.01_linux.runsudo sh cuda_10.2.89_440.33.01_linux.run

Thursday, May 14, 2020

Screen permission denied


Problem
Cannot make directory '/var/run/screen': Permission denied
Solution
sudo /etc/init.d/screen-cleanup start