Installing CUPS on Ubuntu 18.04

Begin by updating the system and installing CUPS along with essential dependencies:

sudo apt update
sudo apt install cups foomatic-filters ghostscript

Restart the CUPS service to apply changes:

sudo systemctl restart cups

Enable and start the service if not already running:

sudo systemctl enable --now cups

Access the CUPS web interface at http://localhost:631 for GUI-based configuration.

If encountering D-Bus errors:

sudo systemctl start dbus

Printer Setup via CLI

Add a network printer using IPP:

lpadmin -p Epson_L3251 -E -v ipp://11.22.33.44/ipp/print -m everywhere
lpadmin -p HP_M104W -E -v ipp://11.22.33.44/ipp/print -m everywhere

Set a default printer:

lpoptions -d Epson_L3251

Print a PDF file:

lp -o media=A4 document.pdf

Check printer status:

lpstat -p

Remove a printer:

lpadmin -x Epson_L3251

Locate PPD files:

lpinfo -m | grep -i epson
find /etc/cups/ppd -name "*Epson*"

Android PDF Printing via Vendor Plugins

Instead of embedding print logic, leverage manufacturer-provided print services:

• HP: com.hp.android.printservice
• Epson: Epson iPrint
• Canon: Canon PRINT Business
• Samsung: Samsung Mobile Print

Use Android’s share intent to delegate printing:

private fun printPdf(pdfPath: String) {
    val file = File(pdfPath)
    if (!file.exists()) {
        Toast.makeText(this, "File not found", Toast.LENGTH_SHORT).show()
        return
    }

    val uri = Uri.fromFile(file)
    val intent = Intent(Intent.ACTION_SEND).apply {
        type = "application/pdf"
        putExtra(Intent.EXTRA_STREAM, uri)
    }
    startActivity(Intent.createChooser(intent, "Print PDF"))
}

Cross-Compiling CUPS for Android (Advanced)

While possible, compiling CUPS for Android is complex and generally discouraged unless absolutely necessary.

Prerequisites

1. Install Android NDK (e.g., r21e).
2. Create a standalone toolchain:

$NDK/build/tools/make_standalone_toolchain.py \
  --arch arm --api 24 --install-dir /opt/toolchain

Set environment variables:

export PATH=/opt/toolchain/bin:$PATH
export CC=armv7a-linux-androideabi24-clang
export CXX=armv7a-linux-androideabi24-clang++

Patching and Building CUPS

CUPS requires modifications for Android compatibility:

• Disable D-Bus, PAM, and TLS.
• Replace missing nl_langinfo implementation (from AOSP sed source).
• Stub out password/group database functions (getpwuid, endpwent, etc.).
• Comment out pthread_cancel usage in threading code.

Example configure command:

./configure \
  --host=arm-linux-androideabi \
  --disable-dbus \
  --disable-pam \
  --without-tls \
  --prefix=/system/usr/root \
  --with-cups-user=system \
  --with-cups-group=system

Apply necessary patches before building:

make
make install DESTDIR=/output

Deployment on Android

After compilation:

1. Push binaries to /system/usr/root/{bin,sbin}.
2. Copy libraries to /system/lib.
3. Place config files in /system/usr/root/etc/cups/.
4. Set permissions:

chmod 755 /system/usr/root -R
chmod 777 /system/usr/root/var -R

Configure cupsd.conf to allow network access:

<Location />
  Order allow,deny
  Allow all
</Location>

Launch CUPS daemon:

export LD_LIBRARY_PATH=/system/usr/root/lib
export PATH=/system/usr/root/bin:/system/usr/root/sbin:$PATH
cupsd -f &

Verify operation by accessing http://localhost:631 via a mobile browser.

Common Issues

• "Unsupported document-format": Requires cups-filters for PDF rendering.
• Backend crashes: Ensure libcups.so.2 is in LD_LIBRARY_PATH.
• PPD creation failure: Confirm printer supports IPP Everywhere via:

ipptool -tv ipp://PRINTER_IP/ipp/print get-printer-attributes.test

Note: Full PDF printing on Android typically requires additional components like cups-filters, qpdf, and image libraries (Poppler, LCMS2, etc.), which must also be cross-compiled and deployed.