The Linux Serial HOWTO

by Greg Hankins, greg.hankins@cc.gatech.edu

1. Introduction

• 1.1 Copyright
• 1.2 New Versions Of This Document
• 1.3 Feedback
• 1.4 Disclaimer

2. Supported Serial Hardware

• 2.1 Standard PC Serial Boards
• 2.2 Plug And Play (PnP) Modems
• 2.3 Dumb Multiport Serial Boards (with 8250/16450/16550A UARTs)
• 2.4 Intelligent Multiport Serial Boards
• 2.5 Unsupported Serial Hardware

3. What Are The Names Of The Serial Ports?

• 3.1 Serial Port Devices and Numbers In /dev
• 3.2 Notes For Dumb Multiport Boards
• 3.3 Notes For Intelligent Multiport Boards

4. Interesting Programs You Should Know About

• 4.1 What is getty?
• 4.2 What is setserial?

5. How Do I Dial Out With My Modem?

• 5.1 Hardware Requirements
• 5.2 Talking To Your Modem
• 5.3 Dial Out Modem Configuration
• 5.4 Hardware Flow Control

6. How Do I Dial In And Out With My Modem Using getty_ps?

• 6.1 Dial In And Out Modem Configuration
• 6.2 Installing getty_ps
• 6.3 Setting up uugetty
• 6.4 Customizing uugetty

7. How Do I Set Up A Terminal Connected To My PC?

• 7.1 Hardware Requirements
• 7.2 Setting up getty
• 7.3 Notes On Setting Up A PC As A Terminal

8. Can I Use More Than Two Serial Devices?

• 8.1 Choosing Serial Device Interrupts
• 8.2 Setting Serial Device Addresses

9. How Do I Set Up My Serial Ports For Higher Speeds? What Speed Should I Use With My Modem?

10. Communications Programs And Utilities

11. Serial Tips And Miscellany

• 11.1 kermit and zmodem
• 11.2 Setting Terminal Types Automagically
• 11.3 Color ls On Serial Connections
• 11.4 Printing To A Printer Connected To A Terminal
• 11.5 Can Linux Configure The Serial Devices Automagically?
• 11.6 Using A Serial Console
• 11.7 Higher Serial Throughput

12. One Step Further...

• 12.1 What Are Lock Files?
• 12.2 ``baud'' Vs. ``bps''
• 12.3 What Are UARTs? How Do They Affect Performance?

13. Troubleshooting

• 13.1 I Keep Getting ``line NNN of inittab invalid''
• 13.2 When I Try To Dial Out, It Says ``/dev/cuaN: Device or resource busy''
• 13.3 I Keep Getting ``Id SN respawning too fast: disabled for 5 minutes''
• 13.4 Serial Devices Are Slow, Or Serial Devices Can Only Send In One Direction
• 13.5 My Modem Is Hosed After Someone Hangs Up, Or uugetty doesn't respawn
• 13.6 I Have My Terminal Connected To My PC, But After I Type In A Login Name, It Just Locks Up
• 13.7 At High Speeds, My Modem Looses Data
• 13.8 On Startup, Linux Doesn't Report The Serial Devices The Way I Have Them Configured
• 13.9 rz And/Or sz Don't Work When I Call My Linux Box On A Modem
• 13.10 My Screen Is Printing Funny Looking Characters
• 13.11 getty Or uugetty Still Doesn't Work

14. Other Sources Of Information

15. Contributions