Create boot disk for serial console

Remote Serial Console HOWTO
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# C.9. Create boot disk for serial console

Once the upgrade has been sucessfully done create a boot floppy which has serial console support. This is most simply done by creating a boot disk, as done by the anaconda installer or as described in Section 2.1; modifying the configuration file `\SYSLINUX.CFG` to configure the boot loader to use the serial console, as described in Section 4.3; and finally configuring the kernel to use the serial console, as described in Section 5.3.

An alternative is to create your own mkbootdisk RPM package containing a modified copy of the shell script `/sbin/mkbootdisk`.

The `\SYSLINUX.CFG` file on the boot floppy is written by mkbootdisk using the code in Figure C-3. We alter this code to use the serial console; the result is shown in Figure C-4.

Figure C-3. Extract from Red Hat Linux 7.2 `mkbootdisk` which creates `SYSLINUX.CFG`

    cat > $MOUNTDIR/syslinux.cfg <<EOF
    default linux
    prompt 1
    display boot.msg
    timeout 100
    label linux
      kernel vmlinuz
      append $INITRDARG root=$rootdev
    EOF

Figure C-4. Altered extract from `mkbootdisk`, which creates a `SYSLINUX.CFG` that uses a serial console

    cat > $MOUNTDIR/syslinux.cfg <<EOF
    serial 0 9600
    default linux
    prompt 1
    display boot.msg
    timeout 100
    label linux
      kernel vmlinuz
      append $INITRDARG root=$rootdev console=tty0 console=ttyS0,9600n8
    EOF

Created boot floppies will now use the serial console.

By far the best alternative would be the addition of parameters to mkbootdisk to allow the kernel parameters and serial port, speed and flow control to be given when the boot floppy is created. For this enhancement request see Red Hat Bugzilla entry 59351.

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