Ubuntu 16.04打印机显示红色感叹号无法打印，网络打印机搜不到求助

Hey there, let's work through this printer problem step by step—those red exclamation marks and missing network entries are definitely frustrating, but we can fix this.

1. First, Confirm Network Connectivity #

Since your printer is connected via LAN, let's make sure your Ubuntu machine can actually reach it:

• Grab your printer's IP address from its physical display (usually in Settings > Network or Status menu).
• Open a terminal (press Ctrl+Alt+T) and run ping [your-printer-ip] (replace with the actual IP). If you get regular replies, your network connection is solid. If not, check the printer's LAN cable/Wi-Fi and your router settings to ensure both devices are on the same network.
• If you don’t know the printer’s IP, run arp -a in the terminal to list all devices on your network—look for entries that match your printer’s brand or model.

2. Clear the Problematic Printer Entry #

That red exclamation mark usually points to a misconfigured existing setup. Let's start fresh:

• Go to System Settings > Printers.
• Right-click the printer with the red exclamation and select Remove to delete it.

3. Manually Add the Network Printer (Since Auto-Detect Isn’t Working) #

Auto-detect can fail for various reasons, so manual setup is the way to go:

• In the Printers window, click the + button.
• When the "New Printer" window opens, scroll to the bottom and select Enter URI.
• Input your printer’s URI using one of these common formats:
  • TCP/IP printers: ipp://[printer-ip]:631/ipp/print or socket://[printer-ip]:9100 (9100 is the standard raw print port)
  • HP printers: hp://[printer-ip]/ (if you don’t have HP’s tools installed, we’ll cover that next)
• Click Forward, then select your printer’s manufacturer and model from the list. If your model isn’t listed, click PPD File to load a driver you’ve downloaded from the printer’s official website.
• Follow the remaining prompts to name the printer and finish setup.

4. Install Missing Printer Drivers #

Ubuntu 16.04 might need additional drivers for some printer brands:

• For HP printers: Run sudo apt-get install hplip hplip-gui in the terminal to install HP’s printer tools. After installation, run hp-setup to walk through a dedicated setup wizard.
• For Canon/Epson/other brands: Open Software & Updates, go to the Additional Drivers tab, and check if there’s a proprietary driver available for your printer. If not, download the .deb driver package from the manufacturer’s site, then install it with sudo dpkg -i [driver-file-name.deb]. If you hit dependency errors, run sudo apt-get install -f to fix them.

5. Restart the Printing Service #

Sometimes glitches in the print spooler cause these issues. Let’s reset it:

• In the terminal, run sudo systemctl restart cups.service.
• Wait 10-15 seconds, then check the Printers window again and try adding the printer once more.

6. Check Firewall Settings #

Ubuntu’s default firewall might be blocking printer communications:

• Run sudo ufw allow 631/tcp and sudo ufw allow 9100/tcp to open the most common printer ports.
• Reload the firewall with sudo ufw reload, then test adding the printer again.

If none of these steps work, double-check that your printer is powered on, free of paper jams/low ink, and that its firmware is up to date (check your printer’s manual for firmware update steps).

内容的提问来源于stack exchange，提问作者Avinash