qBittorrent on Raspberry Pi

…in case you don’t want to spend too much time and have a nice torrent client with web interface installed on your Raspberry Pi, qBittorrent is probably a good option (even full of settings).

Of course, we need to install the package (we install the one with NO GUI, only web interface):

apt install qbittorrent-nox

We also want to create a user with minimum privileges to run this software.
We are going to create a user called torrent part of a new group called torrent as well, within a home directory in /var/torrent
After that, we will add our own user (e.g. user1 to the torrent group, in order to allow you to access the downloaded files.
We are also creating a downloads folder, setting the right permissions.

adduser --system --group --home /var/torrent torrent
adduser user1 torrent
mkdir -p /var/torrent/downloads
chown torrent:torrent /var/torrent/downloads
chmod 770 /var/torrent/downloads

Now we’re going to create a new systemd service file: /etc/systemd/system/qbittorrent-nox.service

[Unit]
Description=BitTorrent Client
After=network.target

[Service]
Type=forking
User=torrent
Group=torrent
UMask=002
ExecStart=/usr/bin/qbittorrent-nox -d --webui-port=8080
Restart=on-failure

[Install]
WantedBy=multi-user.target

Enable and start the service:

systemctl enable qbittorrent-nox
systemctl start qbittorrent-nox

You should now be able to connect to your raspberry pi’s IP, on port 8080.

You will be asked to login.
Note: default username is admin, and the password is adminadmin.
Once logged in, under Settings > WebUI, you can whitelist your local network (e.g. 192.168.10.0/8) to skip authentication.

…and yes, that’s it 😉

I told you it was a quick one!

Enjoy!

rTorrent – ruTorrent – Lighttpd

Messy article, but let’s try to summarise a bit.

We’re going to run a very lightweight Torrent client setup, with graphical interface, on a Debian server (an old raspberry pi, to be precise).

Torrent client: rtorrent
GUI: ruTorrent
Webserver: Lighttpd

Install rtorrent

apt-get install rtorrent

Configure rtorrent to run as a service

Configure user

Let’s create a user torrent to run the rtorrent service

useradd -m -d /var/torrent torrent

Create the service

Create the file /etc/systemd/system/rtorrent.service

[Unit]
Description=rTorrent Daemon
After=network.target

[Service]
[Unit]
Description=rTorrent Daemon
After=network.target

[Service]
Type=simple
KillMode=process
User=torrent
ExecStartPre=/bin/bash -c "if test -e /var/torrent/rtorrent/.session/rtorrent.lock && test -z pidof rtorrent; then rm -f /var/torrent/rtorrent/.session/rtorrent.lock;
 fi"
ExecStart=/usr/bin/rtorrent
WorkingDirectory=/var/torrent/rtorrent
Restart=on-failure
[Install]
WantedBy=multi-user.target

Enable the service

systemctl enable rtorrent

Configure rtorrent for user torrent

As root su - torrent to become torrent user. Then run the following oneliner: (ref. CONFIG Template · rakshasa/rtorrent Wiki · GitHub)

curl -Ls "https://raw.githubusercontent.com/wiki/rakshasa/rtorrent/CONFIG-Template.md" \
    | sed -ne "/^######/,/^### END/p" \
    | sed -re "s:/home/USERNAME:$HOME:" >~/.rtorrent.rc
mkdir -p ~/rtorrent/

Edit your new .rtorrent.rc file accordingly as per below:

# Some extra parameters
dht.mode.set = auto
dht_port = 6881
protocol.pex.set = yes
trackers.use_udp.set = yes

# This will run XMLRPC interface (disabling manual/text mode version)
system.daemon.set = true
scgi_port = 127.0.0.1:5000

Note that port 50000 is the default one that you should open/forward on/from your router.

Install Lighttpd

Let’s install the basic, setting right permissions

apt-get install lighttpd php-cgi
lighty-enable-mod fastcgi 
lighty-enable-mod fastcgi-php

# Get latest ruTorrent package and install
cd /var/www/html/
git clone https://github.com/Novik/ruTorrent.git

chown-R www-data:www-data /var/www/
service lighttpd force-reload

Verify creating a page called test.php into /var/www/html/ with the content <?php phpinfo(); ?> and check in the browser if it works. It should. If not… tough life 😉

Web configuration file for rTorrent: /etc/lighttpd/conf-available/20-rtorrent

server.modules += ( "mod_fastcgi" )
server.modules += ( "mod_scgi" )

mimetype.assign             = (
      ".rpm"          =>      "application/x-rpm",
      ".pdf"          =>      "application/pdf",
      ".sig"          =>      "application/pgp-signature",
      ".spl"          =>      "application/futuresplash",
      ".class"        =>      "application/octet-stream",
      ".ps"           =>      "application/postscript",
      ".torrent"      =>      "application/x-bittorrent",
      ".dvi"          =>      "application/x-dvi",
      ".gz"           =>      "application/x-gzip",
      ".pac"          =>      "application/x-ns-proxy-autoconfig",
      ".swf"          =>      "application/x-shockwave-flash",
      ".tar.gz"       =>      "application/x-tgz",
      ".tgz"          =>      "application/x-tgz",
      ".tar"          =>      "application/x-tar",
      ".zip"          =>      "application/zip",
      ".mp3"          =>      "audio/mpeg",
      ".m3u"          =>      "audio/x-mpegurl",
      ".wma"          =>      "audio/x-ms-wma",
      ".wax"          =>      "audio/x-ms-wax",
      ".ogg"          =>      "application/ogg",
      ".wav"          =>      "audio/x-wav",
      ".gif"          =>      "image/gif",
      ".jar"          =>      "application/x-java-archive",
      ".jpg"          =>      "image/jpeg",
      ".jpeg"         =>      "image/jpeg",
      ".png"          =>      "image/png",
      ".xbm"          =>      "image/x-xbitmap",
      ".xpm"          =>      "image/x-xpixmap",
      ".xwd"          =>      "image/x-xwindowdump",
      ".css"          =>      "text/css",
      ".html"         =>      "text/html",
      ".htm"          =>      "text/html",
      ".js"           =>      "text/javascript",
      ".asc"          =>      "text/plain",
      ".c"            =>      "text/plain",
      ".cpp"          =>      "text/plain",
      ".log"          =>      "text/plain",
      ".conf"         =>      "text/plain",
      ".text"         =>      "text/plain",
      ".txt"          =>      "text/plain",
      ".dtd"          =>      "text/xml",
      ".xml"          =>      "text/xml",
      ".mpeg"         =>      "video/mpeg",
      ".mpg"          =>      "video/mpeg",
      ".mov"          =>      "video/quicktime",
      ".qt"           =>      "video/quicktime",
      ".avi"          =>      "video/x-msvideo",
      ".asf"          =>      "video/x-ms-asf",
      ".asx"          =>      "video/x-ms-asf",
      ".wmv"          =>      "video/x-ms-wmv",
      ".bz2"          =>      "application/x-bzip",
      ".tbz"          =>      "application/x-bzip-compressed-tar",
      ".tar.bz2"      =>      "application/x-bzip-compressed-tar",
      # default mime type
      ""              =>      "application/octet-stream",
     )

scgi.server = ( "/RPC2" =>
    ( "127.0.0.1" =>
        (
            "host" => "127.0.0.1",
            "port" => 5000,
            "check-local" => "disable"
        )
    )
)

fastcgi.server = ( ".php" => ((
                 "bin-path" => "/usr/bin/php-cgi",
                 "socket" => "/tmp/php.socket"
)))

Enable the configuration linking and reload lighttpd

ln -sf /etc/lighttpd/conf-available/20-rtorrent /etc/lighttpd/conf-enable/20-rtorrent
systemctl reload lighttpd

Now, if all went well, you should be able to start the rtorrent service

systemctl start rtorrent

…and theoretically, even open ruTorrent in your browser.

ruTorrent, currently is configured by default to connect to 127.0.0.1:5000. You can change these parameters within its config.php file.

However, we used the default settings in this how to, and you should be able to have it working simply…

http://<ip_of_your_raspberry_pi>/ruTorrent/

Give it a try… and good luck! 😉

Mount Windows Network drives in WSL

In Windows WSL, you can access the local disk navigating the path /mnt/c/ for the C: drive, for example.

Sometimes, network drives mounted on boot aren’t automatically mounted within your WSL Linux shell. You can do it manually using the following commands:

# For a drive already mapped in Windows (e.g. Z: drive)
$ sudo mkdir /mnt/z
$ sudo mount -t drvfs Z: /mnt/z

# For a network drive accessible via \\myserver\dir1 in Explorer
$ sudo mkdir /mnt/dir1
$ sudo mount -t drvfs '\\myserver\dir1' /mnt/dir1

Convert FLV to MP4

Quick and dirty lines to convert FLV files into MP4.

To do so, you need the package ffmpeg.

# Temporary move all the .flv files into a TMP directory
$ find . -type f -name "*.flv" -exec mv {} ../TMP/ \;

# Remove all spaces from the filename
$ cd ../TMP/
$ for file in *' '* ; do mv -- "$file" "${file// /_}" ; done

# Now, convert all the files from FLV to MP4 using ffmpeg
$ for file in `ls` ; do ffmpeg -i "$file" -c copy "${file//flv/mp4}" ; done

During the process, you might get some errors. You will see some .mp4 files with size 0 bites.

You can then try to remove the broken files and try converting re-encoding

# Find and delete files size 0
$ find . -type f -size 0 -print0 | xargs -0 rm

# Try re-encoding
$ for file in `ls *.flv` ; do ffmpeg -i "$file" -vcodec libx264 -acodec copy "${file//flv/mp4}" ; done

GIT tricks when you mess up a bit

Sometimes, especially at the beginning, a Developer makes loads of mistakes and here there are some workaround that can help. 😉

Rewrite master’s history (TO AVOID)

git log --pretty=oneline

git rebase -i --root => s/pick/s => choose what to keep ‘pick‘ and what to remove ‘s‘

-> for each ‘pick’ you need to write a summary in the comments

Rewrite history of the current branch (squash)

Firstly, check how many ahead/behind is your branch comparing to the reference one (e.g. master/main)

STEP 1

git rebase -i HEAD~_number of commits_ (e.g. git rebase -i HEAD~3) => use the number of “ahead’s” that you found.

Make the required changes (pick/s) and save.

Then:
git push origin +mybranch

STEP 2

git rebase
Any conflicts?

YES -> fix them, git add . , git rebase --continue
NO -> git push + (forced push using +)

Fix a wrong merge on master

git revert -m

NOTE: merge commit does NOT count.

A -\
    K
    |
    L
    |
B -/
|
...

Here an example.
You want to go back to commit B (master).
A, B, K, L are commit ID – you can find them using git log command.

From B to A (A is the last merge that we want to delete), there are 2 commits, K and L.

If you want to go back to B:

git revert -m2 A
which means – go back of 2 commits from A

Happy fixing! 🙂

Reverse SSH Tunnel

To allow LOCAL_SERVER behind a firewall/NAT/Home Router to be accessible via SSH from a REMOTE_SERVER you can use a ssh tunnel (reverse).

Basically, from your LOCAL_SERVER you forward port 22 (ssh) to another port on REMOTE_SERVER, for example 8000 and you can ssh into your LOCAL_SERVER from the public IP of the REMOTE_SERVER via port 8000.

To do so, you need to run the following from LOCAL_SERVER:

 local-server: ~ ssh -fNR 8000:localhost:22 <user>@<REMOTE_SERVER>

On REMOTE_SERVER you can use netstat -nlpt to check if there is a service listening on port 8000.

Example:

remote-server ~# netstat -nplt | grep 8000
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      1396/sshd: root
tcp6       0      0 :::8000                 :::*                    LISTEN      1396/sshd: root

In this case, the REMOTE_SERVER allows connection from ALL the interfaces (0.0.0.0) to port 8000.
This means that, if the REMOTE_SERVER has IP 217.160.150.123, if you can connect to LOCAL_SERVER from a THIRD_SERVER using the following:

third-server: ~ ssh -p 8000 <user_local_server>@217.160.150.123

NOTE. If you see that the LISTEN connection on REMOTE_SERVER is bound to 127.0.0.1 and not to 0.0.0.0, it is probably related to the setting GatewayPorts set to no in /etc/ssh/sshd_config on REMOTE_SERVER.
Best setting is clientspecified (rather than yes) as per this post.

Set this value to yes and restart sshd service.

With that setting, you can potentially allow only connection from the REMOTE_SERVER to the LOCAL_SERVER, to increase security.
To do so, you need to use the following ssh command from LOCAL_SERVER:

 local-server: ~ ssh -fNR 127.0.0.1:8000:localhost:22 <user>@<REMOTE_SERVER>

With netstat, you’ll see now this:

remote-server:~# netstat -nplt | grep 8000
tcp        0      0 127.0.0.1:8000          0.0.0.0:*               LISTEN      1461/sshd: root

With this forward, you will be able to access LOCAL_SERVER ONLY from the REMOTE_SERVER itself:

remote-server: ~ ssh -p 8000 <user_local_server>@localhost

I hope this helps 🙂

Happy tunnelling!

Virtualhost and Letsencrypt

Quick guideline about how to install multiple sites on a single server using Virtualhosting, and have the SSL certificate installed and automatically renewed using Letsencrypt.

There are plenty of how to online, but I wanted to have a quick reference page for myself 🙂

Firstly, this has been tested on Debian 12, but it should work on previous Debian versions and Ubuntu too.

Apache setup and virtualhosts

Firstly, install Apache and other packages that you will mostly likely need, especially if you run WordPress or any php based framework:

apt-get install apache2 php php-mysql libapache2-mod-php php-gd php-curl net-tools telnet dos2unix

Now, you should create the folder structure to host your sites. I used /var/www/virtualhosts/<site>/public_html

I made sure permissions were set correctly too:

chown -R www-data:www-data /var/www/
find /var/www -type -d -exec chmod 775 {} \;

Now, create a virtualhost file for each site. In the following example we are going to create the conf file for site1.

Create /etc/apache2/sites-available/site1.conf

<VirtualHost *:80>
    ServerName site1.com
    ServerAlias www.site1.com
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/virtualhosts/site1/public_html

    <Directory /var/www/virtualhosts/site1/public_html>
        Options -Indexes +FollowSymLinks
        AllowOverride All
    </Directory>

    ErrorLog ${APACHE_LOG_DIR}/site1-error.log
    CustomLog ${APACHE_LOG_DIR}/site1-access.log combined
</VirtualHost>

Do the same for all the sites you have.

Once done, upload the content of your sites in public_html folder.

Disable all the default Apache sites and enable the ones you have created. You can use the commands a2dissite and a2ensite or manually create symbolic links into /etc/apache2/sites-enabled/

Check that all the virtualhosts are properly loaded:

source /etc/apache2/envvars
apache2 -S

You should see all your sites under *80 section.
Right now we have enabled only Apache on port 80 to return the sites we have hosted. No 443 yet.

Now, you can use curl to do some tests to see if the virtual hosts are responding correctly.

~ curl -IH'Host: site1.com' http://<server_IP>  # to get the header of site1.com
~ curl -H'Host: site1.com' http://<server_IP>  # to get the full page of site1.com

Hopefully all works (if not, troubleshoot it heheh), let’s point our DNS to our server, and test directly using the domain names.

All good? Cool!

Make sure now that your firewall allows port 80 and port 443. Even if you’re considering to serve your site ONLY over SSL (port 443), the certbot tool that does the auto-renewal of the certificate needs port 80 open.

Installation and configuration of certbot – Letsencrypt

As root, issue the below commands:

apt-get install snapd
snap install core
snap refresh core
snap install --classic certbot
ln -s /snap/bin/certbot /usr/bin/certbot

You have now the certbot tool installed.

Following the above example of site1.com, we are going now to get the SSL certificate for that site (even the www.site1.com one), and let the tool install and configure everything automatically.

certbot --apache -d site1.com -d www.site1.com

Hopefully all goes well 🙂 Repeat for each of your sites accordingly.

Once done with all the sites, just to make sure the auto-renewal works, you can also issue a dry-run check:

certbot renew --dry-run

Letsencrypt certificates last 90 days (afaik), but the certbot tool installed in this way does the auto-renewal in an automatic fashion.
If you’re curios where this is written (you might think about cron but unable to find anything – like it happend to me).
If this is the case, you can try to run this command, and you may find the certbot listed:

systemctl list-timers

More information are available on the official website at this address.

You can now test using curl again, but hitting https instead of http:

~ curl -IH'Host: site1.com' https://<server_IP>  # to get the header of site1.com
~ curl -H'Host: site1.com' https://<server_IP>  # to get the full page of site1.com

Oh, one note.
By default, at least at the time when I’m writing this article, once you install the certificate, the *80 virtualhost of your site will be modified, adding the following lines, which force a 302 redirect from http to https.

RewriteEngine on
RewriteCond %{SERVER_NAME} =www.site1.com [OR]
RewriteCond %{SERVER_NAME} =site1.com
RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [END,NE,R=permanent]

If it’s what you want – cool.
If you still want to serve your site on http AND https, comment out (or delete) those new lines.

Happy virtualhosting and ssl’ing! 🙂

Windows 10 – VMWare Disk cleanup and shrink

Simple batch script to run as Administrator in order to cleanup the disk, defrag and shrink.

Please note that the shrink works only if the VMWare tools are installed on the guest VM.

@ECHO OFF
REM Make sure to run the script as Administrator
whoami /groups | find "S-1-16-12288" > nul

if %errorlevel% == 0 (
 echo Welcome, Admin
) else (
 echo You must run this script as Administrator. Aborting...
 goto EOF
)

REM Enable components to cleanup
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Active Setup Temp Folders" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\BranchCache" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Downloaded Program Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\GameNewsFiles" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\GameStatisticsFiles" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\GameUpdateFiles" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Internet Cache Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Memory Dump Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Offline Pages Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Old ChkDsk Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Previous Installations" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Recycle Bin" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Service Pack Cleanup" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Setup Log Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\System error memory dump files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\System error minidump files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Temporary Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Temporary Setup Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Temporary Sync Files" /V StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Thumbnail Cache" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Update Cleanup" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Upgrade Discarded Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\User file versions" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Windows Defender" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Windows Error Reporting Archive Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Windows Error Reporting Queue Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Windows Error Reporting System Archive Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Windows Error Reporting System Queue Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Windows ESD installation files" /v StateFlags0100 /d 2 /t REG_DWORD /f
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Windows Upgrade Log Files" /v StateFlags0100 /d 2 /t REG_DWORD /f
 
REM Run cleanup
IF EXIST %SystemRoot%\SYSTEM32\cleanmgr.exe START /WAIT cleanmgr /sagerun:100

echo *** DEFRAGGING DRIVES ***
echo DEFRAG C:
defrag c: -f

if not exist "C:\Program Files\VMware\VMware Tools" goto NOVMWARE
echo.
echo *** SHRINKING DRIVES ***
cd "C:\Program Files\VMware\VMware Tools\"
VMwareToolboxCmd.exe disk shrink c:\

if not exist D: goto NODDRIVESHRINK
VMwareToolboxCmd.exe disk shrink D:\
:NODDRIVESHRINK
:NOVMWARE


echo *** SHUTTING DOWN ***
shutdown -s -t 30

:EOF
echo Terminating script
pause

Save this content in a .bat file and… enjoy it!

Manage PDF files

Merge multiple files into single PDF

I’m sure that we all had the need to send a single PDF file, maybe a signed contract. Yes, those 20 or more pages that you need to return, probably with just two of them filled up and signed.

Some PDF give you the ability to digitally sign them. But in my experience, most of them aren’t so modern.

So, what do I do?

I print ONLY the pages that I need to sign, scan them and here I am, with the need to “rebuild” the PDF, replacing the pages signed.

Example.
You have the file contract.pdf, with 20 pages and you need to sign page 10 and page 20.
The scan has a different resolution (or, even worse, it’s a different format, like jpg).

Here the command to make the magic happen:

convert contract.pdf[0-8] mypage10.jpg contract.pdf[10-18] mypage20.jpg -resize 1240x1753 -extent 1240x1753 -gravity center -units PixelsPerInch -density 150x150 contract_signed.pdf

The bit before -resize is pretty self explanatory. The bit after is a way to have the size of all pages fitting an A4 format, with a good printable resolution.

Of course, to make this happen, you need Linux (or WSL on Windows 10) and imagemagick installed.

Another way is using ghostscript.

A simple Ghostscript command to merge two PDFs in a single file is shown below:

gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=combine.pdf -dBATCH 1.pdf 2.pdf

What about a quick onliner to reduce and convert to grayscale your pdf?

ghostscript -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -sProcessColorModel=DeviceGray -sColorConversionStrategy=Gray -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

PDF size reduce

Sometimes instead, you need to reduce the size of an existing PDF. Here a handy oneliner, using ghostscript:

ghostscript -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/printer -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

Other options for PDFSETTINGS:

/screen selects low-resolution output similar to the Acrobat Distiller “Screen Optimized” setting.
/ebook selects medium-resolution output similar to the Acrobat Distiller “eBook” setting.
/printer selects output similar to the Acrobat Distiller “Print Optimized” setting.
/prepress selects output similar to Acrobat Distiller “Prepress Optimized” setting.
/default selects output intended to be useful across a wide variety of uses, possibly at the expense of a larger output file.

Happy PDF’ing 🙂

Sources:
https://stackoverflow.com/questions/23214617/imagemagick-convert-image-to-pdf-with-a4-page-size-and-image-fit-to-page
https://www.shellhacks.com/merge-pdf-files-linux-command-line/
https://gist.github.com/firstdoit/6390547

Migrate Linux Subsystem from one PC to another

Are you enjoying your favorite Linux distro running within the Windows 10 Linux Subsystem?

Have you configured all nicely?

What happened if you get a new pc and you’d like to migrate your VM across?

This is what happened to me. And looking around, I found this post that gave me this kinda-dirty way, but did work!

After that, I decided to review the steps, and I’ve added these directories in the exclude’s list, to make clearer the process of export/import:

/dev
/proc
/sys
/run
/tmp
/media
/mnt
/var/cache
/var/run

Of course, if you have important data in these folders and you want to move across too, just update the one-liner below accordingly. 😉

On your OLD PC

Open your Linux VM
Get inside your Downloads directory (replace <user> with your username):

cd /mnt/c/Users/<user>/Downloads
Make sure to be root (sudo su -)
Run:

tar -cvpzf backup.tar.gz --exclude=/backup.tar.gz --exclude=/dev --exclude=/proc --exclude=/sys --exclude=/run --exclude=/tmp --exclude=/media --exclude=/mnt --exclude=/var/cache --exclude=/var/run --one-file-system /

NOTE: you could achieve the same using the option --exclude-from=file.txt, and having the list of exclusions in this file. I used a one-liner as it’s quicker to copy and paste.
Once done, close your Linux VM
Verify that you have a new file called backup.tar.bz in Downloads

On your NEW PC

Install from Microsoft Store the same Linux VM (or reinstall in the same way you have done originally on your old pc)
Copy across your backup.tar.bz within your new Downloads folder
Open the VM that you’ve just installed (minimal setup – this will be completely overwritten, so don’t be bothered too much)
Once you’re inside and your backup.tar.bz is in Download, run the following (replace <user> with your username):

sudo tar -xpzf /mnt/c/Users/<user>/Downloads/backup.tar.gz -C / --numeric-owner
Ignore the errors
Close and re-open the VM: DONE! 🙂

Happy migration! 😉

My notepad

Chris' IT notes…