[2024-feb-29] Sad news: Eric Layton aka Nocturnal Slacker aka vtel57 passed away on Feb 26th, shortly after hospitalization. He was one of our Wiki's most prominent admins. He will be missed.
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| Both sides previous revisionPrevious revisionNext revision | Previous revision | ||
| howtos:general_admin:serial_console [2012/12/20 02:16 (UTC)] – [Sources] added author tag mfillpot | howtos:general_admin:serial_console [2014/11/14 09:18 (UTC)] (current) – add GRUB2 section fdonkers | ||
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| + | <!-- Reviewed 2013-01-06 mfillpot --> | ||
| <!-- Add your text below. We strongly advise to start with a Headline (see button bar above). --> | <!-- Add your text below. We strongly advise to start with a Headline (see button bar above). --> | ||
| ====== Serial Console ====== | ====== Serial Console ====== | ||
| + | Slackware can be installed on various embedded devices. A lot of those don't | ||
| + | have a traditional console, like a monitor and keyboard. Instead, the console | ||
| + | is often routed to the serial port. In order to take advantage of this, some | ||
| + | post-install configuration is necessary. | ||
| - | Slackware can be installed on various embedded devices. A lot of those don't have a traditional console, like a monitor and keyboard. Instead, the console is often routed to the serial port. In order to take advantage of this, some post-install configuration is necessary. | + | This howto can also be used to setup a serial console on an existing headless |
| - | + | server as a backup for administering the machine. | |
| - | This howto can also be used to setup a serial console on an existing headless server as a backup for administering the machine. | + | |
| ====== Preparation ====== | ====== Preparation ====== | ||
| + | You need to know the serial device and the speed. The device will mostly be | ||
| + | ttyS0, the first serial device. If you are using a serial to USB adapter, it | ||
| + | will likely be ttyUSB0. Consult the documentation of your board if you are | ||
| + | not sure. | ||
| - | You need to know the serial device | + | Some devices have an option in the BIOS to change |
| + | settings. Make sure you know the speed that is currently set. | ||
| - | Some devices have an option in the BIOS to change the speed and other serial settings. Make sure you know the speed that is currently set. | + | In the below examples we will assume ttyS0 with speed 38400. |
| - | + | ||
| - | In the below examples we will assume ttyS0 with speed 38400. | + | |
| ====== Host configuration ====== | ====== Host configuration ====== | ||
| - | |||
| ===== Activate serial port ===== | ===== Activate serial port ===== | ||
| + | Edit ''/ | ||
| + | the speed setting when required. | ||
| - | Edit '' | + | <file - / |
| - | + | ||
| - | <code> | + | |
| # Local serial lines: | # Local serial lines: | ||
| s1: | s1: | ||
| # | # | ||
| - | </code> | + | </file> |
| ===== Allow root login ===== | ===== Allow root login ===== | ||
| - | + | Edit ''/ | |
| - | Edit ''/ | + | login via the serial console. You can omit this step if you will access the |
| - | + | machine with a normal user id. | |
| - | <code> | + | <file - / |
| # These are some remote ttys, and uncommenting them might be less than fully secure: | # These are some remote ttys, and uncommenting them might be less than fully secure: | ||
| ttyS0 | ttyS0 | ||
| # | # | ||
| - | </code> | + | </file> |
| ===== Setup LILO boot loader ===== | ===== Setup LILO boot loader ===== | ||
| - | + | Edit ''/ | |
| - | Edit ''/ | + | <file - / |
| - | <code> | + | |
| serial=0, | serial=0, | ||
| - | </code> | + | </file> |
| - | The 0 refers to the first serial device, ttyS0. | + | The 0 refers to the first serial device, ttyS0. |
| - | Add the following parameter to the kernel line: | + | Add the following parameter to the kernel line: |
| - | <code> | + | <file - / |
| append=" | append=" | ||
| - | </code> | + | </file> |
| - | If the '' | + | If the //append// line already exists, add the parameter as follows: |
| - | <code> | + | <file - / |
| append=" | append=" | ||
| - | </code> | + | </file> |
| Now run ''/ | Now run ''/ | ||
| - | To have the console on normal tty as well as serial port, adjust the kernel line as follows: | + | To have the console on normal tty as well as serial port, adjust the |
| - | + | kernel line as follows: | |
| - | <code> | + | <file - / |
| append=" | append=" | ||
| - | </code> | + | </file> |
| - | ===== Setup GRUB boot loader ===== | + | ===== Setup GRUB-legacy |
| + | Edit ''/ | ||
| - | Edit ''/ | ||
| - | |||
| Add lines to the general section as follows: | Add lines to the general section as follows: | ||
| - | + | <file - / | |
| - | <code> | + | |
| serial --speed=38400 | serial --speed=38400 | ||
| terminal serial | terminal serial | ||
| - | </code> | + | </file> |
| Add the following parameter to the kernel line: | Add the following parameter to the kernel line: | ||
| - | <code> | + | <file - / |
| console=ttyS0, | console=ttyS0, | ||
| - | </code> | + | </file> |
| - | The complete kernel line might look like this: | + | The complete kernel line might look like this (substitute your root |
| - | + | partition and vmlinuz file): | |
| - | <code> | + | <file - / |
| kernel / | kernel / | ||
| - | </code> | + | </file> |
| - | To have the console on normal tty as well as serial port, adjust the terminal and kernel lines as follows: | + | To have the console on normal tty as well as serial port, adjust the |
| - | + | terminal and kernel lines as follows: | |
| - | <code> | + | <file - / |
| terminal --timeout=5 serial console | terminal --timeout=5 serial console | ||
| - | </code><code> | + | </file> |
| + | <file - / | ||
| kernel xxx console=tty0 console=ttyS0, | kernel xxx console=tty0 console=ttyS0, | ||
| + | </ | ||
| + | |||
| + | When the terminal timeout expires, the first option (in this case serial) | ||
| + | will be chosen as the console. The normal bootloader timeout will start | ||
| + | when the terminal timeout ends. | ||
| + | |||
| + | ===== Setup GRUB2 boot loader ===== | ||
| + | Edit file ''/ | ||
| + | <file . grub> | ||
| + | GRUB_CMDLINE_LINUX_DEFAULT=" | ||
| + | </ | ||
| + | |||
| + | Add the following lines to define the console settings: | ||
| + | <file . grub> | ||
| + | GRUB_TERMINAL=serial | ||
| + | GRUB_SERIAL_COMMAND=" | ||
| + | </ | ||
| + | |||
| + | Now rebuild the GRUB2 configuration: | ||
| + | < | ||
| + | # grub-mkconfig -o / | ||
| </ | </ | ||
| - | |||
| - | When the terminal timeout expires, the first option (in this case serial) will be chosen as the console. The normal bootloader timeout will start when the terminal timeout ends. | ||
| ====== Connect from a remote computer ====== | ====== Connect from a remote computer ====== | ||
| + | To use the serial console, you need to attach a second computer to the | ||
| + | serial port of the host. Use a null modem cable. Most modern computers no | ||
| + | longer have a serial port so you might need a serial to USB connector as | ||
| + | well. | ||
| - | To use the serial console, you need to attach a second computer to the serial port of the host. Use a null modem cable. Most modern computers no longer have a serial port so you might need a serial to USB connector as well. | + | Once you have physically connected the machines, you need a communications |
| - | + | package to interact with the console. Two popular options are **screen** | |
| - | Once you have physically connected the machines, you need a communications package to interact with the console. Two popular options are //screen// and //minicom//. | + | and **minicom**. |
| ===== Connect using screen ===== | ===== Connect using screen ===== | ||
| + | This is the easiest option because it doesn' | ||
| + | Start **screen** and specify the serial device and the desired speed on the | ||
| + | command line. | ||
| + | < | ||
| + | user@darkstar$ screen / | ||
| + | </ | ||
| - | This is the easiest option because | + | ===== Connect using minicom ===== |
| + | Before using minicom, you need to configure | ||
| + | as follows: | ||
| < | < | ||
| - | screen / | + | user@darkstar$ minicom -s |
| </ | </ | ||
| - | |||
| - | ===== Connect using minicom ===== | ||
| - | |||
| - | Before using minicom, you need to configure it. Start with the '' | ||
| - | |||
| - | < | ||
| You will see the main menu. | You will see the main menu. | ||
| - | |||
| < | < | ||
| | | ||
| Line 130: | Line 158: | ||
| </ | </ | ||
| - | Select //Serial port setup//. You will see the serial port settings. | + | Select //Serial port setup//. You will see the serial port settings. |
| < | < | ||
| +-----------------------------------------------------------------------+ | +-----------------------------------------------------------------------+ | ||
| Line 146: | Line 173: | ||
| </ | </ | ||
| - | Use the < | + | Use the < |
| + | Make sure the //device// and // | ||
| + | < | ||
| + | //Modem and dialing// option. On the detail screen, make sure the | ||
| + | //Init string// and //Reset string// options are empty. Hit < | ||
| + | again to return to the main screen. Now you can save your options. Use | ||
| + | //Save setup as dfl// to save this as your new default. Use | ||
| + | //Save setup as..// to save as a certain profile. | ||
| - | Call minicom again and the new options will take effect. | + | Call minicom again and the new options will take effect. |
| - | + | < | |
| - | < | + | user@darkstar$ |
| + | </ | ||
| Or you can start with a certain configuration | Or you can start with a certain configuration | ||
| + | < | ||
| + | user@darkstar$ minicom myprofile | ||
| + | </ | ||
| - | < | + | Use <key>C-a</ |
| - | + | to quit. | |
| - | Use <key>CTRL-A</ | + | |
| ====== Troubleshooting ====== | ====== Troubleshooting ====== | ||
| - | |||
| ===== Garbled characters in terminal ===== | ===== Garbled characters in terminal ===== | ||
| - | + | When you see progress in the terminal but the characters are garbled and | |
| - | When you see progress in the terminal but the characters are garbled and unreadable, make sure you have the same speed set in the following sections: BIOS, bootloader and inittab. Also make sure your client connects with the same speed. | + | unreadable, make sure you have the same speed set in the following |
| + | sections: BIOS, bootloader and inittab. Also make sure your client connects | ||
| + | with the same speed. | ||
| ===== Unable to sign on as root ===== | ===== Unable to sign on as root ===== | ||
| - | + | Check the '' | |
| - | Check the '' | + | |
| ===== Unable to use screen or minicom as a regular user ===== | ===== Unable to use screen or minicom as a regular user ===== | ||
| - | |||
| When you get authorization problems using the serial device, make sure your user is in the '' | When you get authorization problems using the serial device, make sure your user is in the '' | ||
| ====== Further reading ====== | ====== Further reading ====== | ||
| - | + | | |
| - | | + | * screen [[http:// |
| - | * screen [[http:// | + | |
| * '' | * '' | ||
| Line 190: | Line 225: | ||
| <!-- You must remove the tag-word " | <!-- You must remove the tag-word " | ||
| {{tag> | {{tag> | ||
| + | |||
