[PATCH] xend: update init script to avoid grep on non-existent file system

[PATCH] xend: update init script to avoid grep on non-existent file system

[Richie]

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I'm seeing a grep error during bare metal pvops kernel boot.  In the 
init script, the previous checks will avoid/perform the /proc/xen mount 
as appropriate, but then it does a grep on /proc/xen/capabilities 
without ensuring that /proc/xen is actually mounted.  This is my attempt 
(read: first patch :) ) to avoid it.

[-- Attachment #2: xend.patch --]
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# HG changeset patch
# User Richie <listmail@triad.rr.com>
# Date 1273894781 14400
# Node ID 90705b2abd84e75971d12dead966191731ab1361
# Parent  baccadfd9418b8dee931945e5752cb118f5bf3cb
xend: update init script to avoid grep on non-existent file system

diff -r baccadfd9418 -r 90705b2abd84 tools/hotplug/Linux/init.d/xend
--- a/tools/hotplug/Linux/init.d/xend	Fri May 14 08:05:05 2010 +0100
+++ b/tools/hotplug/Linux/init.d/xend	Fri May 14 23:39:41 2010 -0400
@@ -31,7 +31,8 @@
 	mount -t xenfs xenfs /proc/xen
 fi
 
-if ! grep -q "control_d" /proc/xen/capabilities ; then
+if ! test -d /proc/xen || \
+   ! grep -q "control_d" /proc/xen/capabilities ; then
 	exit 0
 fi
 

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Re: [PATCH] xend: update init script to avoid grep on non-existent file system

[Keir Fraser]

On 15/05/2010 05:16, "Richie" <listmail@triad.rr.com> wrote:

> I'm seeing a grep error during bare metal pvops kernel boot.  In the
> init script, the previous checks will avoid/perform the /proc/xen mount
> as appropriate, but then it does a grep on /proc/xen/capabilities
> without ensuring that /proc/xen is actually mounted.  This is my attempt
> (read: first patch :) ) to avoid it.

Richie,

Can you try adding the -s option to grep instead (i.e., grep -qs)? Should be
a simpler way to achieve the same thing. I'll apply that instead if it works
okay for you.

 -- Keir

Re: [PATCH] xend: update init script to avoid grep on non-existent file system

[Richie]

Sure. I agree much simpler, but is this blurb in the grep manpage a concern?
-s, --no-messages
Suppress error messages about nonexistent or unreadable files.
Portability note: unlike GNU grep, 7th Edition Unix grep did not
conform to POSIX, because it lacked -q and its -s option behaved
like GNU grep’s -q option. USG-style grep also lacked -q but
its -s option behaved like GNU grep. *Portable shell scripts
should avoid both -q and -s and should redirect standard and
error output to /dev/null instead*. (-s is specified by POSIX.)

I'm not sure where all the xend daemon can run? is it always running on 
linux, thus implying (modern?) GNU grep? The reason I am bringing this 
up is that I recall having grep related issues when running git on 
Solaris (without gnu utilities installed) for this very reason. I will 
re-sumbit accordingly.


Keir Fraser wrote:
> On 15/05/2010 05:16, "Richie" <listmail@triad.rr.com> wrote:
>
>   
>> I'm seeing a grep error during bare metal pvops kernel boot.  In the
>> init script, the previous checks will avoid/perform the /proc/xen mount
>> as appropriate, but then it does a grep on /proc/xen/capabilities
>> without ensuring that /proc/xen is actually mounted.  This is my attempt
>> (read: first patch :) ) to avoid it.
>>     
>
> Richie,
>
> Can you try adding the -s option to grep instead (i.e., grep -qs)? Should be
> a simpler way to achieve the same thing. I'll apply that instead if it works
> okay for you.
>
>  -- Keir
>
>
>   

Re: [PATCH] xend: update init script to avoid grep on non-existent file system

[Keir Fraser]

On 15/05/2010 15:56, "Richie" <listmail@triad.rr.com> wrote:

> 
> I'm not sure where all the xend daemon can run? is it always running on
> linux, thus implying (modern?) GNU grep? The reason I am bringing this
> up is that I recall having grep related issues when running git on
> Solaris (without gnu utilities installed) for this very reason. I will
> re-sumbit accordingly.

Well, it's a Linux-specific hotplug script thet you're editing, isn't it.

 -- Keir

Re: [PATCH] xend: update init script to avoid grep on non-existent file system

[Richie]

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Keir Fraser wrote:
> On 15/05/2010 05:16, "Richie" <listmail@triad.rr.com> wrote:
>
>   
>> I'm seeing a grep error during bare metal pvops kernel boot.  In the
>> init script, the previous checks will avoid/perform the /proc/xen mount
>> as appropriate, but then it does a grep on /proc/xen/capabilities
>> without ensuring that /proc/xen is actually mounted.  This is my attempt
>> (read: first patch :) ) to avoid it.
>>     
>
> Richie,
>
> Can you try adding the -s option to grep instead (i.e., grep -qs)? Should be
> a simpler way to achieve the same thing. I'll apply that instead if it works
> okay for you.
>
>  -- Keir
>
>
>   


[-- Attachment #2: xend_v2.patch --]
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# HG changeset patch
# User Richie <listmail@triad.rr.com>
# Date 1273938512 14400
# Node ID cc3ed74cfef3f4504712d1d53c0af8c8940e9ab8
# Parent  baccadfd9418b8dee931945e5752cb118f5bf3cb
xend: suppress errors during capabilities check

diff -r baccadfd9418 -r cc3ed74cfef3 tools/hotplug/Linux/init.d/xend
--- a/tools/hotplug/Linux/init.d/xend	Fri May 14 08:05:05 2010 +0100
+++ b/tools/hotplug/Linux/init.d/xend	Sat May 15 11:48:32 2010 -0400
@@ -31,7 +31,7 @@
 	mount -t xenfs xenfs /proc/xen
 fi
 
-if ! grep -q "control_d" /proc/xen/capabilities ; then
+if ! grep -qs "control_d" /proc/xen/capabilities ; then
 	exit 0
 fi
 

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