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Alex | 1 May 2010 21:27
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Re: deleted perl hacks in /tmp

Hi,

Some time ago Chris was trying to track down some cracker using perl
to breach his system:

On Fri, Apr 16, 2010 at 5:27 PM, Chris <chris <at> deksai.com> wrote:
>> Is changing the filesystem type an option?  You could temporarily
>> create a new non-extn filesystem on a free partition and mount it on
>> /tmp.
>> In that case, you could  set the undeletable attribute on /tmp
>> ("chattr +U /tmp").  It will be inherited by any file created there.
>> Problem is that extn doesn't honour the attribute, though you could
>> patch it if you prefer (cf. http://lwn.net/Articles/211193/).

How did it work out? Were you able to mount undeletable? Did you find
out which files they were? Do you now have plans to rebuild the
system?

Best,
Alex
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query | 15 May 2010 16:52
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Clarification needed reg Linux behaviour of Swap space and Swap activity

Hi ,

We are seeing high memory usage on our Prod host running RHEL 4.  The
host is running Java server
and the application server is consuming around 2.2 G of memory as
reported by top .

===
Tasks: 449 total,   1 running, 448 sleeping,   0 stopped,   0 zombie
Cpu(s): 12.9% us,  0.1% sy,  0.0% ni, 87.0% id,  0.0% wa,  0.0% hi,
0.0% si
Mem:   8160920k total,  8088752k used,    72168k free,    75516k
buffers
Swap:  8388600k total,  3651908k used,  4736692k free,   807556k
cached

  PID USER      PR  NI %CPU    TIME+  %MEM  VIRT  RES  SHR S
COMMAND
31712 nobody    16   0  100 286:20.91 14.4 1458m 1.1g  12m S
java_daemon
18427 nobody    16   0    2 391:17.48 27.7 4334m 2.2g 6200 S
java_daemon
===

sar is also reporting around 40 percent swap space being consumed.
This swap space usage varies between 30 percent and 50 percent and it
remains like this always .
But when checked with vmstat I can see no swap activity being taken
place . I monitored for around 15 minutes and can see no swap activity
 although sar is reporting around 40 percent swap space being consumed
(Continue reading)

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Glynn Clements | 15 May 2010 20:18

Re: Clarification needed reg Linux behaviour of Swap space and Swap activity


query wrote:

> 1    Can there be any impact in performance as there is no swap
> activity .

No.

> Also , would like to know why swap space is getting
> consumed when there is no swap activity being taken place .

If a program has a large number of subsystems, many of these may
rarely be used, resulting in the associated memory getting swapped out
and remaining swapped out.

This is more common for interpreted languages, as they often read
and/or generate data in memory, whereas a compiled program would just
map the data from the executable or library.

This isn't really a problem, it just means that you need sufficient
swap space. Storing data in swap space doesn't impact performance if
it isn't being accessed.

> Is it a sign of application leaking memory.

Not necessarily.

> 2. Will disabling memory overcommit will help in improving memory usage .

No.
(Continue reading)

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Mr Robert Ehis | 16 May 2010 11:53

Funds.

Please confirm if you are interseted in the Inheritance. If yes, 
contact me through email robertehis78 <at> yahoo.com.hk by sending your Telephone 
number, full name, occupation, age, nationality and full address.
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ZakMed | 17 May 2010 23:03
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query | 18 May 2010 07:20
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How to check whethera disk supports 32-bit IO

Hi All ,

    I want to know enable 32-bit IO-support on my SATA hard drive
using hdparm . But before I enable 32-bit support , I want to know
whether my hard drive supports 32-bit IO or not.

    I tried the -I option with hdparm , but it is not telling clearly
whether it supports 32-bit or not.

    The following is the output from the hard drive of my system (hdparm -I ) .

    =====
   Commands/features:
	Enabled	Supported:
	   *	NOP cmd
	   *	READ BUFFER cmd
	   *	WRITE BUFFER cmd
	   *	Host Protected Area feature set
	   *	Look-ahead
	   *	Write cache
	   *	Power Management feature set
		Security Mode feature set
	   *	SMART feature set
	   *	FLUSH CACHE EXT command
	   *	Mandatory FLUSH CACHE command
	   *	Device Configuration Overlay feature set
	   *	48-bit Address feature set
(is it telling that the disk supports 48-bit IO)
		Automatic Acoustic Management feature set
		SET MAX security extension
(Continue reading)

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Glynn Clements | 18 May 2010 15:43

Re: How to check whethera disk supports 32-bit IO


query wrote:

>     I want to know enable 32-bit IO-support on my SATA hard drive
> using hdparm . But before I enable 32-bit support , I want to know
> whether my hard drive supports 32-bit IO or not.

The term "32-bit I/O" relates to communication between the CPU and a
PCI IDE controller. The concept isn't meaningful for an on-board
controller.

As for communication between the controller and the drive, a parallel
ATA interface is 16-bit, while SATA is serial.

> 	   *	48-bit Address feature set
> (is it telling that the disk supports 48-bit IO)

No, it's stating that the drive supports 48-bit LBA addresses. The
original IDE standard used 28-bit addresses which limit the size of
the drive to 137GB (2^28 512-byte sectors).

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Glynn Clements <glynn <at> gclements.plus.com>
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query | 19 May 2010 06:02
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Re: How to check whethera disk supports 32-bit IO

On Tue, May 18, 2010 at 7:13 PM, Glynn Clements
<glynn <at> gclements.plus.com> wrote:

Thanks for the clarification .  Need some further clarification...
>
> query wrote:
>
>>     I want to know enable 32-bit IO-support on my SATA hard drive
>> using hdparm . But before I enable 32-bit support , I want to know
>> whether my hard drive supports 32-bit IO or not.
>
> The term "32-bit I/O" relates to communication between the CPU and a
> PCI IDE controller.

"The hdpam man page say "32-bit" refers to data transfers across a PCI
or VLB bus to the interface  card  only ". So , here does the
interface card is referring to the CPU.

> The concept isn't meaningful for an on-board controller.

By On-board controller do you mean to say hardware RAID device or SCSI
devices and we don't have  to set IO parameter
in such devices.

>
> As for communication between the controller and the drive, a parallel
> ATA interface is 16-bit, while SATA is serial.
>
>>          *    48-bit Address feature set
>> (is it telling that the disk supports 48-bit IO)
(Continue reading)

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Glynn Clements | 19 May 2010 16:38

Re: How to check whethera disk supports 32-bit IO


query wrote:

> >>     I want to know enable 32-bit IO-support on my SATA hard drive
> >> using hdparm . But before I enable 32-bit support , I want to know
> >> whether my hard drive supports 32-bit IO or not.
> >
> > The term "32-bit I/O" relates to communication between the CPU and a
> > PCI IDE controller.
> 
> "The hdpam man page say "32-bit" refers to data transfers across a PCI
> or VLB bus to the interface  card  only ". So , here does the
> interface card is referring to the CPU.

"Interface card" means a card that plugs into a PCI or VLB slot (VLB =
VESA Local Bus, an alternative standard for expansion cards which
superseded ISA but was itself superseded by PCI).

> > The concept isn't meaningful for an on-board controller.
> 
> By On-board controller do you mean to say hardware RAID device or SCSI
> devices and we don't have  to set IO parameter
> in such devices.

I mean an IDE controller that's built into the Southbridge.

In any case, you won't find a SATA controller using 16-bit transfers.

> > As for communication between the controller and the drive, a parallel
> > ATA interface is 16-bit, while SATA is serial.
(Continue reading)

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Alex | 20 May 2010 21:14
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Find latest RPM in directory

Hi all,

I'm not really a perl programmer, but know that perl and the perl-RPM
package would be really good at finding the latest RPM package among
all those in directory, and printing them out. Does anyone know of an
existing script that can do such a thing?

I'd like to be able to run something like:

# find-latest-pkg openssh-clients

and have it print out only the latest, instead of all ten versions
that may be in the directory. Even better, it would be great to print
out only the latest unique packages in directory, and not have to
specify the package name at all!

Perhaps more applicable to an RPM mailing list, or one specific to
perl-RPM, but hopefully you also consider this linux-admin material.

Thanks so much.
Best regards,
Alex
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