Virtual Paperless-ngx printer on Raspberry Pi

README.md

What is this?

These are instructions to create a virtual "printer" for Paperless-ngx that runs on Raspberry Pi (I use Raspberry Pi Zero W). This way, you can "print" documents from your computer or phone, and they'll be submitted to your Paperless-ngx instance.

Instructions

Create a dedicated user in your Paperless-ngx instance on the Users & Groups page. It doesn't need too many permissions.

On your Raspberry Pi, run the following:

sudo apt-get update
sudo apt-get install cups cups-filters cups-tea4cups avahi-daemon

Place cupsd.conf from this gist into /etc/cups/cupsd.conf. Place tea4cups.conf from this gist into /etc/cups/tea4cups.conf. Place upload-to-paperless.sh into /usr/local/bin/upload-to-paperless.sh. Update variables at the top of the script with your values. Make sure it's executable:

sudo chmod +x /usr/local/bin/upload-to-paperless.sh

Restart cups daemon

sudo systemctl restart cups

Create the virtual printer

sudo lpadmin -p Paperless -v tea4cups:// -E -m raw -o printer-is-shared=true

The printer should now become visible

cupsd.conf

#
# Configuration file for the CUPS scheduler.  See "man cupsd.conf" for a
# complete description of this file.
#

# Log general information in error_log - change "warn" to "debug"
# for troubleshooting...
LogLevel warn
PageLogFormat

# Specifies the maximum size of the log files before they are rotated.  The value "0" disables log rotation.
MaxLogSize 0

# Default error policy for printers
ErrorPolicy retry-job

# Only listen for connections from the local machine.
Port 631
Listen /run/cups/cups.sock

# Show shared printers on the local network.
Browsing Yes
BrowseLocalProtocols dnssd

# Default authentication type, when authentication is required...
DefaultAuthType Basic

# Web interface setting...
WebInterface Yes

# Timeout after cupsd exits if idle (applied only if cupsd runs on-demand - with -l)
IdleExitTimeout 60

# Restrict access to the server...
<Location />
  Order allow,deny
  Allow @LOCAL
</Location>

# Restrict access to the admin pages...
<Location /admin>
  Order allow,deny
  Allow @LOCAL
</Location>

# Restrict access to configuration files...
<Location /admin/conf>
  AuthType Default
  Require user @SYSTEM
  Order allow,deny
</Location>

# Restrict access to log files...
<Location /admin/log>
  AuthType Default
  Require user @SYSTEM
  Order allow,deny
</Location>

# Set the default printer/job policies...
<Policy default>
  # Job/subscription privacy...
  JobPrivateAccess default
  JobPrivateValues default
  SubscriptionPrivateAccess default
  SubscriptionPrivateValues default

  # Job-related operations must be done by the owner or an administrator...
  <Limit Create-Job Print-Job Print-URI Validate-Job>
    Order deny,allow
  </Limit>

  <Limit Send-Document Send-URI Hold-Job Release-Job Restart-Job Purge-Jobs Set-Job-Attributes Create-Job-Subscription Renew-Subscription Cancel-Subscription Get-Notifications Reprocess-Job Cancel-Current-Job Suspend-Current-Job Resume-Job Cancel-My-Jobs Close-Job CUPS-Move-Job>
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  <Limit CUPS-Get-Document>
    AuthType Default
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  # All administration operations require an administrator to authenticate...
  <Limit CUPS-Add-Modify-Printer CUPS-Delete-Printer CUPS-Add-Modify-Class CUPS-Delete-Class CUPS-Set-Default CUPS-Get-Devices>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # All printer operations require a printer operator to authenticate...
  <Limit Pause-Printer Resume-Printer Enable-Printer Disable-Printer Pause-Printer-After-Current-Job Hold-New-Jobs Release-Held-New-Jobs Deactivate-Printer Activate-Printer Restart-Printer Shutdown-Printer Startup-Printer Promote-Job Schedule-Job-After Cancel-Jobs CUPS-Accept-Jobs CUPS-Reject-Jobs>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # Only the owner or an administrator can cancel or authenticate a job...
  <Limit Cancel-Job CUPS-Authenticate-Job>
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  <Limit All>
    Order deny,allow
  </Limit>
</Policy>

# Set the authenticated printer/job policies...
<Policy authenticated>
  # Job/subscription privacy...
  JobPrivateAccess default
  JobPrivateValues default
  SubscriptionPrivateAccess default
  SubscriptionPrivateValues default

  # Job-related operations must be done by the owner or an administrator...
  <Limit Create-Job Print-Job Print-URI Validate-Job>
    AuthType Default
    Order deny,allow
  </Limit>

  <Limit Send-Document Send-URI Hold-Job Release-Job Restart-Job Purge-Jobs Set-Job-Attributes Create-Job-Subscription Renew-Subscription Cancel-Subscription Get-Notifications Reprocess-Job Cancel-Current-Job Suspend-Current-Job Resume-Job Cancel-My-Jobs Close-Job CUPS-Move-Job CUPS-Get-Document>
    AuthType Default
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  # All administration operations require an administrator to authenticate...
  <Limit CUPS-Add-Modify-Printer CUPS-Delete-Printer CUPS-Add-Modify-Class CUPS-Delete-Class CUPS-Set-Default>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # All printer operations require a printer operator to authenticate...
  <Limit Pause-Printer Resume-Printer Enable-Printer Disable-Printer Pause-Printer-After-Current-Job Hold-New-Jobs Release-Held-New-Jobs Deactivate-Printer Activate-Printer Restart-Printer Shutdown-Printer Startup-Printer Promote-Job Schedule-Job-After Cancel-Jobs CUPS-Accept-Jobs CUPS-Reject-Jobs>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # Only the owner or an administrator can cancel or authenticate a job...
  <Limit Cancel-Job CUPS-Authenticate-Job>
    AuthType Default
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  <Limit All>
    Order deny,allow
  </Limit>
</Policy>

# Set the kerberized printer/job policies...
<Policy kerberos>
  # Job/subscription privacy...
  JobPrivateAccess default
  JobPrivateValues default
  SubscriptionPrivateAccess default
  SubscriptionPrivateValues default

  # Job-related operations must be done by the owner or an administrator...
  <Limit Create-Job Print-Job Print-URI Validate-Job>
    AuthType Negotiate
    Order deny,allow
  </Limit>

  <Limit Send-Document Send-URI Hold-Job Release-Job Restart-Job Purge-Jobs Set-Job-Attributes Create-Job-Subscription Renew-Subscription Cancel-Subscription Get-Notifications Reprocess-Job Cancel-Current-Job Suspend-Current-Job Resume-Job Cancel-My-Jobs Close-Job CUPS-Move-Job CUPS-Get-Document>
    AuthType Negotiate
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  # All administration operations require an administrator to authenticate...
  <Limit CUPS-Add-Modify-Printer CUPS-Delete-Printer CUPS-Add-Modify-Class CUPS-Delete-Class CUPS-Set-Default>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # All printer operations require a printer operator to authenticate...
  <Limit Pause-Printer Resume-Printer Enable-Printer Disable-Printer Pause-Printer-After-Current-Job Hold-New-Jobs Release-Held-New-Jobs Deactivate-Printer Activate-Printer Restart-Printer Shutdown-Printer Startup-Printer Promote-Job Schedule-Job-After Cancel-Jobs CUPS-Accept-Jobs CUPS-Reject-Jobs>
    AuthType Default
    Require user @SYSTEM
    Order deny,allow
  </Limit>

  # Only the owner or an administrator can cancel or authenticate a job...
  <Limit Cancel-Job CUPS-Authenticate-Job>
    AuthType Negotiate
    Require user @OWNER @SYSTEM
    Order deny,allow
  </Limit>

  <Limit All>
    Order deny,allow
  </Limit>
</Policy>

tea4cups.conf

[global]
debug : yes

[Paperless]
prehook_rawpdf : /usr/local/bin/upload-to-paperless.sh "$TEATITLE" "$TEADATAFILE"

upload-to-paperless.sh

#!/bin/bash

SERVER_URL="https://paperless.example.com" # Paperless-ngx instance URL
PAPERLESS_USERNAME="printer"               # Paperless-ngx account created for use by this script
PAPERLESS_PASSWORD="<PASSWORD>"            # Password for the aforementioned account
PAPERLESS_INBOX_TAG_ID="<ID>"              # ID (not name!) of your inbox tag in Paperless-ngx. 
                                           # See https://docs.paperless-ngx.com/usage/#basic-searching for Best Practices

if [ "$#" -lt 2 ]; then
    echo "Usage: $0 title file" >&2
    exit 1
fi

TITLE=$1
INPUT_FILE_PATH="$2"

if [ -z "$INPUT_FILE_PATH" ] || [ ! -f "$INPUT_FILE_PATH" ]; then
    echo "No file provided" >&2
    exit 1
fi

conversion_output_file=$(mktemp)
upload_response_file=$(mktemp)

cleanup() {
    rm -f "$conversion_output_file"
    rm -f "$upload_response_file"
}

trap cleanup EXIT

OUTPUT_FILE_PATH="$conversion_output_file"
ps2pdf "$INPUT_FILE_PATH" "$OUTPUT_FILE_PATH"

RESPONSE=$(curl -s -o "${upload_response_file}" -w "%{http_code}" -X POST "${SERVER_URL}/api/documents/post_document/" \
    -u "${PAPERLESS_USERNAME}:${PAPERLESS_PASSWORD}" \
    -F "document=@${OUTPUT_FILE_PATH}" \
    -F "title=${TITLE}" \
    -F "tags=${PAPERLESS_INBOX_TAG_ID}")

if [ "$RESPONSE" -ne 200 ]; then
    echo "FAILED: $(cat $upload_response_file)" >&2
    exit 1
fi

echo "Upload successful" >&2
exit 0