Note for CentOS 4 users

@rjp:

Centos 4.5 just got pushed out, so a yum update will upgrade your system. It will install the kudzu package (hardware detection - useless on a UML system), which will cause a hang (or perhaps just a long delay - I lost patience) when booting. To prevent this, once the update has finished, use the command:

chkconfig kudzu off

before you reboot to prevent it from running during the boot process.

It takes 3 minutes to run kudzu because it detects 64 serial ports (ttyS*) - UML maps those to pty's on the host and so kudzu tries to probe them to see if there's any equipment on them.

Not sure why linode has that feature enabled (Chris?) but removing the ttyS* entries from /dev before kudzu runs (eg via an rc script) will also work.

@sweh:

It takes 3 minutes to run kudzu because it detects 64 serial ports (ttyS*) - UML maps those to pty's on the host and so kudzu tries to probe them to see if there's any equipment on them.
I don't believe this is accurate. It depends on the command line arguments to UML. For instance, our UMLs map ttyS0 to standard in/out on the host, and that's how we run it inside a screen. The rest of the ttyS devices are nulled (not host:/dev/null, just null :)).

-Chris

@caker:

@sweh:

It takes 3 minutes to run kudzu because it detects 64 serial ports (ttyS*) - UML maps those to pty's on the host and so kudzu tries to probe them to see if there's any equipment on them.
I don't believe this is accurate. It depends on the command line arguments to UML. For instance, our UMLs map ttyS0 to standard in/out on the host, and that's how we run it inside a screen. The rest of the ttyS devices are nulled (not host:/dev/null, just null :)).

-Chris

If I cat /dev/ttyS0, cat /dev/ttyS1, cat /dev/ttyS2 on my linode then dmesg output says:

Serial line 0 assigned device '/dev/ptyp0'
Serial line 1 assigned device '/dev/ptyp1'
Serial line 2 assigned device '/dev/ptyp2'

Are you sure it's not assigning pty's on the host?

The console is assigned to /dev/tty0 and not ttyS0. Any output I send to /dev/ttyS0 (eg "echo hello > /dev/ttyS0") doesn't show on the console

Hmm, the command line passed is

Kernel command line: mem=256M fake_ide fakehd con=null con0=fd:0,fd:1 devfs=nomount root=/dev/ubda ubda=/dev/vg1/sweh-36078 ubdb=/dev/vg1/sweh-7867 ubdc=/dev/vg1/sweh-7870 ubdd=/dev/vg1/sweh-8496 eth0=tuntap,sweh_0,fe:fd:42:a0:8d:69 token_max=800000 token_refill=512 ro

I see no "ssl" option there to turn off the serial ports which the FAQ ( http://user-mode-linux.sourceforge.net/ … html#ss5.1">http://user-mode-linux.sourceforge.net/UserModeLinux-HOWTO-5.html#ss5.1 ) suggests is the right option.

Or am I missing something?

@sweh:

Or am I missing something?
Nope, you are correct; I am wrong, all because of this:

2.6.21.1-linode32 --showconfig | grep pty
CONFIG_SSL_CHAN="pty"

I get that removed next kernel release. I could have sworn I tuned that off. And you're right about the tty0 console. My brain gets full, ya know? I need BrainDoubler [reference to RamDoubler on ancient Mac systems (it did on disk virtual memory)]

Thanks for the heads up.

-Chris

@caker:

I need BrainDoubler
I've got BrainDoubler - but it keeps cra