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Serial console to RHEL6 on Dell R310?

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  Serial console to RHEL6 on Dell R310? Jeremiah DeWitt Weiner <jdw@panix.com> - 2011-06-13 21:19 +0000
    Re: Serial console to RHEL6 on Dell R310? Tim Watts <tw@dionic.net> - 2011-06-13 23:45 +0100
      Re: Serial console to RHEL6 on Dell R310? Jeremiah DeWitt Weiner <jdw@panix.com> - 2011-06-14 15:37 +0000
        Re: Serial console to RHEL6 on Dell R310? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2011-06-14 20:25 +0300
          Re: Serial console to RHEL6 on Dell R310? Jeremiah DeWitt Weiner <jdw@panix.com> - 2011-06-16 19:35 +0000
        Re: Serial console to RHEL6 on Dell R310? Bill Marcum <bill@lat.localnet> - 2011-06-14 16:20 -0400
    Re: Serial console to RHEL6 on Dell R310? Todd <Todd@invalid.com> - 2011-06-13 20:51 -0700
      Re: Serial console to RHEL6 on Dell R310? The Natural Philosopher <tnp@invalid.invalid> - 2011-06-14 11:04 +0100
      Re: Serial console to RHEL6 on Dell R310? Doug Freyburger <dfreybur@yahoo.com> - 2011-06-14 14:32 +0000

#503 — Serial console to RHEL6 on Dell R310?

	I'm trying to set up a new server so I can get to a serial console
on it.  The server is a Dell PowerEdge R310, and the OS is Red Hat
Enterprise Linux 6.  The problem is that no matter what I do, I'm unable
to get a login prompt on the serial line, from a remote machine running
minicom.

	I tried following these directions:
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Technical_Notes/deployment.html
No dice.  (It should be noted that /etc/serial/init.conf suggests a
different approach.)

	I tried manually starting an agetty on the serial port.  No luck -
it would run, but I couldn't get a login prompt on the remote machine.

	I tried setting kernel arguments in grub as described here:
http://www.dell.com/content/topics/global.aspx/power/en/ps1q03_stanton?c=us&cs=555&l=en&s=biz
No luck.  The agetty is running, but I'm still unable to connect.
I tried turning SELinux off, in case that had something to do with it.
I tried setting a serial console in grub.  Nothing worked.  No output on
the serial console.

	I know the cable and remote machine are good, because I can use
minicom and that cable to connect to the console port of a network
switch, and that works fine.  I know the serial port itself works
because I can use it to connect _out_ to a network switch.  So what the
hell is going on?  Any suggestions much appreciated...


-- 
Oh to have a lodge in some vast wilderness.  Where rumors of oppression
and deceit, of unsuccessful and successful wars may never reach me
anymore.  
	-- William Cowper, 1731 - 1800

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#505

Jeremiah DeWitt Weiner wrote:

> I'm trying to set up a new server so I can get to a serial console
> on it.  The server is a Dell PowerEdge R310, and the OS is Red Hat
> Enterprise Linux 6.  The problem is that no matter what I do, I'm unable
> to get a login prompt on the serial line, from a remote machine running
> minicom.
> 
> I tried following these directions:
> http://docs.redhat.com/docs/en-
US/Red_Hat_Enterprise_Linux/6/html/Technical_Notes/deployment.html
> No dice.  (It should be noted that /etc/serial/init.conf suggests a
> different approach.)
> 
> I tried manually starting an agetty on the serial port.  No luck -
> it would run, but I couldn't get a login prompt on the remote machine.
> 
> I tried setting kernel arguments in grub as described here:
> 
http://www.dell.com/content/topics/global.aspx/power/en/ps1q03_stanton?c=us&cs=555&l=en&s=biz
> No luck.  The agetty is running, but I'm still unable to connect.
> I tried turning SELinux off, in case that had something to do with it.
> I tried setting a serial console in grub.  Nothing worked.  No output on
> the serial console.
> 
> I know the cable and remote machine are good, because I can use
> minicom and that cable to connect to the console port of a network
> switch, and that works fine.  I know the serial port itself works
> because I can use it to connect _out_ to a network switch.  So what the
> hell is going on?  Any suggestions much appreciated...
> 
> 

Couple of things:

Has linux (well, udev) made you a /dev/ttyS0 or /dev/ttyS1 device?

Next I'd try

bash < /dev/ttyS0 > /dev/ttyS0 2>&1

and see if there's life at the other end.

stty -a < /dev/ttyS0

should give you the current serial config.

Lack of grub rules out SElinux - it seems to be something a little more 
fundamental.

-- 
Tim Watts

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#514

Tim Watts <tw@dionic.net> wrote:
> Has linux (well, udev) made you a /dev/ttyS0 or /dev/ttyS1 device?

	Yes, the devices are there.

crw-------. 1 root root 	4, 64 Jun 13 17:20 /dev/ttyS0
crw-------. 1 root root 	4, 65 Jun 13 17:18 /dev/ttyS1


> Next I'd try
> bash < /dev/ttyS0 > /dev/ttyS0 2>&1
> and see if there's life at the other end.

	Nothing there.  The agetty is running -
 PID	TTY		STAT	TIME	COMMAND
1650	ttyS0	Ss+		0:00	/sbin/agetty /dev/ttyS0 9600 vt100-nav
- but I get nothing back when running that shell.


> stty -a < /dev/ttyS0
> should give you the current serial config.

	That looks OK...not going to retype the whole thing, but:
speed 9600 baud; rows 0; columns 0; line = 0;
- the rest looks pretty normal.

	Now here is the really weird thing...connecting ttyS0 on the target
server to the console port of one of our network switches (with the getty
still running on the server!) and running minicom, I hit Enter a couple
times and see:

ServerIronADX 1000>
ServerIronADX 1000>Red Hat Enterprise Linux Server release 6.1 (Santiago)
Invalid input

and then further intermixed switch login prompts, server login prompts,
and error messages from both devices.  So the server _is_ outputting a
login prompt on the serial console!  But then why doesn't it show up
anywhere else?  This is breaking my brain.  All I can think of is that
there's some misconfiguration somewhere, but some of the hardware is
also doing some autocorrection or something...crazy, but I'm kind of out
of other ideas.


-- 
Oh to have a lodge in some vast wilderness.  Where rumors of oppression
and deceit, of unsuccessful and successful wars may never reach me
anymore.  
	-- William Cowper, 1731 - 1800

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#517

On 14.6.11 6:37 , Jeremiah DeWitt Weiner wrote:
> Tim Watts<tw@dionic.net>  wrote:
>> Has linux (well, udev) made you a /dev/ttyS0 or /dev/ttyS1 device?
>
> 	Yes, the devices are there.
>
> crw-------. 1 root root 	4, 64 Jun 13 17:20 /dev/ttyS0
> crw-------. 1 root root 	4, 65 Jun 13 17:18 /dev/ttyS1
>
>
>> Next I'd try
>> bash<  /dev/ttyS0>  /dev/ttyS0 2>&1
>> and see if there's life at the other end.
>
> 	Nothing there.  The agetty is running -
>   PID	TTY		STAT	TIME	COMMAND
> 1650	ttyS0	Ss+		0:00	/sbin/agetty /dev/ttyS0 9600 vt100-nav
> - but I get nothing back when running that shell.
>
>
>> stty -a<  /dev/ttyS0
>> should give you the current serial config.
>
> 	That looks OK...not going to retype the whole thing, but:
> speed 9600 baud; rows 0; columns 0; line = 0;
> - the rest looks pretty normal.
>
> 	Now here is the really weird thing...connecting ttyS0 on the target
> server to the console port of one of our network switches (with the getty
> still running on the server!) and running minicom, I hit Enter a couple
> times and see:
>
> ServerIronADX 1000>
> ServerIronADX 1000>Red Hat Enterprise Linux Server release 6.1 (Santiago)
> Invalid input
>
> and then further intermixed switch login prompts, server login prompts,
> and error messages from both devices.  So the server _is_ outputting a
> login prompt on the serial console!  But then why doesn't it show up
> anywhere else?  This is breaking my brain.  All I can think of is that
> there's some misconfiguration somewhere, but some of the hardware is
> also doing some autocorrection or something...crazy, but I'm kind of out
> of other ideas.
>
>

The switch serial port is configured as a DCE (modem), and the
computer serial port is configured as a DTE, and I guess that your
cable is a straight cable.

You need a null-modem cable.

-- 

Tauno Voipio

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#562

Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:
> The switch serial port is configured as a DCE (modem), and the
> computer serial port is configured as a DTE, and I guess that your
> cable is a straight cable.

> You need a null-modem cable.

	You know, I bet that that's it...it's been a long time since I had
to think about serial communications!  I'll try and get my hands on a
null-modem cable and see if that does it.  Thanks for the advice -



-- 
Oh to have a lodge in some vast wilderness.  Where rumors of oppression
and deceit, of unsuccessful and successful wars may never reach me
anymore.  
	-- William Cowper, 1731 - 1800

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#521

On 2011-06-14, Jeremiah DeWitt Weiner <jdw@panix.com> wrote:
> Tim Watts <tw@dionic.net> wrote:
>> Has linux (well, udev) made you a /dev/ttyS0 or /dev/ttyS1 device?
>
> 	Yes, the devices are there.
>
> crw-------. 1 root root 	4, 64 Jun 13 17:20 /dev/ttyS0
> crw-------. 1 root root 	4, 65 Jun 13 17:18 /dev/ttyS1
>
>
>> Next I'd try
>> bash < /dev/ttyS0 > /dev/ttyS0 2>&1
>> and see if there's life at the other end.
>
> 	Nothing there.  The agetty is running -
>  PID	TTY		STAT	TIME	COMMAND
> 1650	ttyS0	Ss+		0:00	/sbin/agetty /dev/ttyS0 9600 vt100-nav
> - but I get nothing back when running that shell.
>
>
>> stty -a < /dev/ttyS0
>> should give you the current serial config.
>
> 	That looks OK...not going to retype the whole thing, but:
> speed 9600 baud; rows 0; columns 0; line = 0;
> - the rest looks pretty normal.
>
> 	Now here is the really weird thing...connecting ttyS0 on the target
> server to the console port of one of our network switches (with the getty
> still running on the server!) and running minicom, I hit Enter a couple
> times and see:
>
> ServerIronADX 1000>
> ServerIronADX 1000>Red Hat Enterprise Linux Server release 6.1 (Santiago)
> Invalid input
>
> and then further intermixed switch login prompts, server login prompts,
> and error messages from both devices.  So the server _is_ outputting a
> login prompt on the serial console!  But then why doesn't it show up
> anywhere else?  This is breaking my brain.  All I can think of is that
> there's some misconfiguration somewhere, but some of the hardware is
> also doing some autocorrection or something...crazy, but I'm kind of out
> of other ideas.
>
Are you running minicom on the same port that getty is running on? Run it
through a null modem cable to another port or another machine. Depending
what you're using as a serial terminal, maybe you can use pppd instead.


-- 
Linux and Windows both win.
Best Documentary Feature: March of the Penguins
Best Picture: Crash

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#506

On 06/13/2011 02:19 PM, Jeremiah DeWitt Weiner wrote:
> 	I'm trying to set up a new server so I can get to a serial console
> on it.  The server is a Dell PowerEdge R310, and the OS is Red Hat
> Enterprise Linux 6.  The problem is that no matter what I do, I'm unable
> to get a login prompt on the serial line, from a remote machine running
> minicom.
>
> 	I tried following these directions:
> http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Technical_Notes/deployment.html
> No dice.  (It should be noted that /etc/serial/init.conf suggests a
> different approach.)
>
> 	I tried manually starting an agetty on the serial port.  No luck -
> it would run, but I couldn't get a login prompt on the remote machine.
>
> 	I tried setting kernel arguments in grub as described here:
> http://www.dell.com/content/topics/global.aspx/power/en/ps1q03_stanton?c=us&cs=555&l=en&s=biz
> No luck.  The agetty is running, but I'm still unable to connect.
> I tried turning SELinux off, in case that had something to do with it.
> I tried setting a serial console in grub.  Nothing worked.  No output on
> the serial console.
>
> 	I know the cable and remote machine are good, because I can use
> minicom and that cable to connect to the console port of a network
> switch, and that works fine.  I know the serial port itself works
> because I can use it to connect _out_ to a network switch.  So what the
> hell is going on?  Any suggestions much appreciated...
>
>

Hi Jeremiah,

I am going to be of little help here.  Sorry.  Mainly
just moral support.

I did this on Solaris about 20 years ago and have little
memory of what I did.  Somewhere in the back of my head,
I remember you had to configure /etc/inittab with
a respawn on your serial ports.

The following is my inittab HylaFax respawn on my six serial
ports:

# Run gettys in standard runlevels
1:2345:respawn:/sbin/mingetty tty1
2:2345:respawn:/sbin/mingetty tty2
3:2345:respawn:/sbin/mingetty tty3
4:2345:respawn:/sbin/mingetty tty4
5:2345:respawn:/sbin/mingetty tty5
6:2345:respawn:/sbin/mingetty tty6

Sorry for not being more help.  Would love to
know what you eventually come up with.

-T

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#508

Todd wrote:
> On 06/13/2011 02:19 PM, Jeremiah DeWitt Weiner wrote:
>>     I'm trying to set up a new server so I can get to a serial console
>> on it.  The server is a Dell PowerEdge R310, and the OS is Red Hat
>> Enterprise Linux 6.  The problem is that no matter what I do, I'm unable
>> to get a login prompt on the serial line, from a remote machine running
>> minicom.
>>
>>     I tried following these directions:
>> http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Technical_Notes/deployment.html 
>>
>> No dice.  (It should be noted that /etc/serial/init.conf suggests a
>> different approach.)
>>
>>     I tried manually starting an agetty on the serial port.  No luck -
>> it would run, but I couldn't get a login prompt on the remote machine.
>>
>>     I tried setting kernel arguments in grub as described here:
>> http://www.dell.com/content/topics/global.aspx/power/en/ps1q03_stanton?c=us&cs=555&l=en&s=biz 
>>
>> No luck.  The agetty is running, but I'm still unable to connect.
>> I tried turning SELinux off, in case that had something to do with it.
>> I tried setting a serial console in grub.  Nothing worked.  No output on
>> the serial console.
>>
>>     I know the cable and remote machine are good, because I can use
>> minicom and that cable to connect to the console port of a network
>> switch, and that works fine.  I know the serial port itself works
>> because I can use it to connect _out_ to a network switch.  So what the
>> hell is going on?  Any suggestions much appreciated...
>>
>>
> 
> Hi Jeremiah,
> 
> I am going to be of little help here.  Sorry.  Mainly
> just moral support.
> 
> I did this on Solaris about 20 years ago and have little
> memory of what I did.  Somewhere in the back of my head,
> I remember you had to configure /etc/inittab with
> a respawn on your serial ports.
> 
> The following is my inittab HylaFax respawn on my six serial
> ports:
> 
> # Run gettys in standard runlevels
> 1:2345:respawn:/sbin/mingetty tty1
> 2:2345:respawn:/sbin/mingetty tty2
> 3:2345:respawn:/sbin/mingetty tty3
> 4:2345:respawn:/sbin/mingetty tty4
> 5:2345:respawn:/sbin/mingetty tty5
> 6:2345:respawn:/sbin/mingetty tty6
> 
> Sorry for not being more help.  Would love to
> know what you eventually come up with.
> 
> -T

yebbut its changed a bit on RHEL 6.

 From years of doing this but years ago, the fiorst step is to put 
something on the port itself like an old modem, and see if you can 'cu' 
to it.

If that works its then down to getting a getty to respawn on the port 
via whatver convoluted reinvented wheel the thing has, and, if you want 
to login as root, making sure its got the privileges to do that.

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#512

Todd wrote:
>
> I did this on Solaris about 20 years ago and have little
> memory of what I did.  Somewhere in the back of my head,
> I remember you had to configure /etc/inittab with
> a respawn on your serial ports.

On Solaris one of the problems was modem settings on serial lines. 
Since Linux boxes tend to have their console on KVM I have not needed to
do much serial line debugging on Linux boxes.  Typically a crash cart
with a laptop running Hyperterm is available and it works when it is
plugged in.

Tim Watts already posted the starting point to debug modem settings,
parity and baud rates on serial lines:

> stty -a < /dev/ttyS0
> should give you the current serial config.

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