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Old 04-27-2011, 08:14 PM
 
Default ssh in while in fsck

My manager reminds me that "in the old Sun days", the ssh server came up
first, *before* the fsck on boot, so that if there was a problem, and fsck
was waiting for an answer, you could remotely ssh in, kill it, restart it,
and answer (or give it the right flags).

Does anyone know if it's possible to have that happen with CentOS? It
would be nice to have it boot that way, so that if you checked, and
figured it should have been up already, you could handle the problem
without coming in....

mark

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Old 04-27-2011, 08:22 PM
Brian Mathis
 
Default ssh in while in fsck

On Wed, Apr 27, 2011 at 4:14 PM, <m.roth@5-cent.us> wrote:
> My manager reminds me that "in the old Sun days", the ssh server came up
> first, *before* the fsck on boot, so that if there was a problem, and fsck
> was waiting for an answer, you could remotely ssh in, kill it, restart it,
> and answer (or give it the right flags).
>
> Does anyone know if it's possible to have that happen with CentOS? It
> would be nice to have it boot that way, so that if you checked, and
> figured it should have been up already, you could handle the problem
> without coming in....
>
> * * * *mark


I think having a decent remote console is the solution to that. DRAC,
KVMoIP, Serial console, etc... I'm not sure how it could be
considered safe to start services like sshd before the filesystem has
been checked.


// Brian Mathis
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Old 04-27-2011, 08:22 PM
John R Pierce
 
Default ssh in while in fsck

On 04/27/11 1:14 PM, m.roth@5-cent.us wrote:
> My manager reminds me that "in the old Sun days", the ssh server came up
> first, *before* the fsck on boot, so that if there was a problem, and fsck
> was waiting for an answer, you could remotely ssh in, kill it, restart it,
> and answer (or give it the right flags).

not on any Sun I've ever seen. fsck happens before TCP or much of
anything else

maybe he's confusing the serial consoles of the Sun's, which were
usually attached to Console servers that you could ssh into ?


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Old 04-27-2011, 08:28 PM
 
Default ssh in while in fsck

Brian Mathis wrote:
> On Wed, Apr 27, 2011 at 4:14 PM, <m.roth@5-cent.us> wrote:
>> My manager reminds me that "in the old Sun days", the ssh server came up
>> first, *before* the fsck on boot, so that if there was a problem, and
>> fsck was waiting for an answer, you could remotely ssh in, kill it,
restart
>> it, and answer (or give it the right flags).
>>
>> Does anyone know if it's possible to have that happen with CentOS? It
>> would be nice to have it boot that way, so that if you checked, and
>> figured it should have been up already, you could handle the problem
>> without coming in....
>
> I think having a decent remote console is the solution to that. DRAC,
> KVMoIP, Serial console, etc... I'm not sure how it could be
> considered safe to start services like sshd before the filesystem has
> been checked.

Hmm, now *that's* an interesting thought: with, say, DRAC, could you ssh
into a management server, then go to a booting system?

mark

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Old 04-27-2011, 08:33 PM
Hakan Koseoglu
 
Default ssh in while in fsck

On 27/04/11 21:28, m.roth@5-cent.us wrote:
> Hmm, now *that's* an interesting thought: with, say, DRAC, could you ssh
> into a management server, then go to a booting system?
It is usually web (and Java) based, running on a different IP address
through the DRAC/ILO port.
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Old 04-27-2011, 09:25 PM
Brian Mathis
 
Default ssh in while in fsck

On Wed, Apr 27, 2011 at 4:28 PM, <m.roth@5-cent.us> wrote:
> Brian Mathis wrote:
>> On Wed, Apr 27, 2011 at 4:14 PM, *<m.roth@5-cent.us> wrote:
>>> My manager reminds me that "in the old Sun days", the ssh server came up
>>> first, *before* the fsck on boot, so that if there was a problem, and
>>> fsck was waiting for an answer, you could remotely ssh in, kill it,
> restart
>>> it, and answer (or give it the right flags).
>>>
>>> Does anyone know if it's possible to have that happen with CentOS? It
>>> would be nice to have it boot that way, so that if you checked, and
>>> figured it should have been up already, you could handle the problem
>>> without coming in....
>>
>> I think having a decent remote console is the solution to that. *DRAC,
>> KVMoIP, Serial console, etc... *I'm not sure how it could be
>> considered safe to start services like sshd before the filesystem has
>> been checked.
>
> Hmm, now *that's* an interesting thought: with, say, DRAC, could you ssh
> into a management server, then go to a booting system?
>
> * * * mark


A DRAC can provide:
- Web interface to server control and monitoring functions
- Remote console (KVM)
- SSH login to a command-line server control
- SSH login to Serial console redirect

I haven;t used the SSH part that much. However, DRAC is Dell
specific, and must be purchased with the server. With remote console,
you might be able to get in, but I'm not sure if the other gettys are
running before the fsck starts.

// Brian Mathis
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Old 04-27-2011, 09:37 PM
Keith Keller
 
Default ssh in while in fsck

On Wed, Apr 27, 2011 at 05:25:22PM -0400, Brian Mathis wrote:
>
> With remote console,
> you might be able to get in, but I'm not sure if the other gettys are
> running before the fsck starts.

With a true serial console you get access to 'the' console, where the
message about proceeding with the fsck would normally appear. The
remote serial console HOWTO is old but covers this ground fairly well:

http://tldp.org/HOWTO/Remote-Serial-Console-HOWTO/index.html

It addresses getting access to the BIOS, the bootloader, and the kernel
/ getty, so you have access to pretty much the entire boot process.
This has saved my bacon quite a few times.

Serial console aggregators run less than $1000, and you can ssh into
them to get access to a given console. On mine, for example, I might do

ssh admin:deadbox@serial-console.example.com

to get to deadbox's console.

--keith

--
kkeller@wombat.san-francisco.ca.us

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Old 04-27-2011, 10:30 PM
Stephen Harris
 
Default ssh in while in fsck

On Wed, Apr 27, 2011 at 04:14:48PM -0400, m.roth@5-cent.us wrote:
> My manager reminds me that "in the old Sun days", the ssh server came up
> first, *before* the fsck on boot, so that if there was a problem, and fsck

Define "old Sun". SunOS 3 and 4 never had ssh. Solaris 2.x, Solaris
7, Solaris 8 never came with ssh out of box. Solaris 9 was the first
version to come with (a broken) SSH as part of the standard build.

> was waiting for an answer, you could remotely ssh in, kill it, restart it,
> and answer (or give it the right flags).

No. You could do it on the console (as others have said) and so with a
serial console connected to a terminal server, or with later-day LOM
devices, you could get to the console "out of band".

Sun, in fact, were the poster boys for needing to fsck because they threw
a lot of stuff onto /usr and had /usr as a separate partition. And many
many of the shared libraries were in /usr/lib, so you could only run
statically linked programs (normally in /sbin) before filesystems were
mounted. SunOS 4 didn't even have "cat" available, so the startup scripts
had a shcat() function which used shell builtins to emulate it.

--

rgds
Stephen
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Old 04-28-2011, 12:52 AM
Devin Reade
 
Default ssh in while in fsck

m.roth@5-cent.us <m.roth@5-cent.us> wrote:

> My manager reminds me that "in the old Sun days", the ssh server came up
> first, *before* the fsck on boot

As others have indicated, but not in so many words, your manager is
out to lunch in this case: ssh, once it was introduced, was started
at run level 3 (or the equivalent, for SunOS 4, which wasn't SYSV).

On old Sun hardware, you could connect to the serial port to get console.
(You could also have a graphical console if you had the add-in video
cards, but people rarely used those for anything but workstations.)
If your serial console was on a console server or serial aggregator
(like a modem server in reverse), then you could telnet into it to
get console on the Sun box.

Later, the serial console was augmented by the ALOM (which predates
the DRAC for Dells). Originally you could only telnet into it (using
a separate management ethernet connection) which means you should
have your management interface on a separate admin net.

Between 5 and 10 years ago, Sun got around to introducing SSH to
the ALOM. At *that* point, you could ssh into a Sun to get console.
Everything is relative, but I wouldn't refer to that as "the old Sun
days", unless you're meaning "before Oracle".

As I've mentioned on other threads, if you need this kind of functionality
for an x86 box that doesn't have its own ALOM/DRAC/iLO (all manufacturer
names for similar functions), I'd suggest the AdderLink iPEPS (network
only) or iPEPS/DA (network + local kybd/monitor/mouse). It uses
encrypted VNC instead of SSH, and can be teamed with an electronic
KVM switch to allow you to use it with multiple machines.

Devin
--
I don't suffer from insanity. I enjoy every minute of it.

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Old 04-28-2011, 07:05 AM
Bent Terp
 
Default ssh in while in fsck

On Wed, Apr 27, 2011 at 10:28 PM, <m.roth@5-cent.us> wrote:
> Hmm, now *that's* an interesting thought: with, say, DRAC, could you ssh
> into a management server, then go to a booting system?

I'd recommend you use a vpn connection instead, so you can go straight
to the iDRAC/ILO/RSA2 (Dell/HP/IBM, respectively) using ssh and https

That way you can powercycle the server, access the bios, and work in
the console without a running sshd.

BR Bent
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