Possible bug with fsimage/pygrub

Possible bug with fsimage/pygrub

[Ian Murray]

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All,
Having a very strange problem. I created a CentOS 7 PV vm but could not get pygrub to pick-up the grub entries. I did some fault finding and concluded that `fsimage` was unable to find the grub.cfg.
I could start the vm as an HVM guest with no problem. I renamed the `grub2` folder to be `grub2.x` and `cp -a` that back to `grub2`. pygrub/fsimage were able to find the file after that. fsimage couldn't see grub2.x/grub.cfg.

 I wrote small test case in python to illustrate the issue:
I can only think it is a bug in fsimage, or there is something very hidden about that directory that is causing this.
Any suggestions would be most welcome,
Thanks,
Ian
import fsimagefs = fsimage.open('/dev/xen2/email', 1048576, "seclabel")if fs.file_exists('/grub2.x/grub.cfg'):  print "found"else:  print "not found"if fs.file_exists('/grub2/grub.cfg'):  print "found"else:  print "not found"
The results are:-  # python ~/test.py not foundfound
(mounted locally, after an update, but same behaviour as previously. The partition is on LVM and is formatted ext4)# ls -al grub2*grub2:total 52drwxr-xr-x. 6 root root  4096 May 31 02:39 .dr-xr-xr-x. 7 root root  4096 May 31 02:41 ..-rw-r--r--. 1 root root    86 Jan 10 23:32 device.mapdrwxr-xr-x. 2 root root  4096 Jan 10 23:32 fonts-rw-r--r--. 1 root root  4806 May 31 02:39 grub.cfg-rw-r--r--. 1 root root  4045 Jan 10 23:33 grub.cfg.1496194637.rpmsave-rw-r--r--. 1 root root  1024 May 31 02:39 grubenvdrwxr-xr-x. 2 root root 12288 Jan 10 23:32 i386-pcdrwxr-xr-x. 2 root root  4096 Jan 10 23:32 localedrwxr-xr-x. 3 root root  4096 Jan 10 23:28 themes-rw-r--r--. 1 root root     0 May 31 02:13 xxxx
grub2.x:total 44drwxr-xr-x. 6 root root  4096 May 31 02:13 .dr-xr-xr-x. 7 root root  4096 May 31 02:41 ..-rw-r--r--. 1 root root    86 Jan 10 23:32 device.mapdrwxr-xr-x. 2 root root  4096 Jan 10 23:32 fonts-rw-r--r--. 1 root root  4045 Jan 10 23:33 grub.cfg-rw-r--r--. 1 root root  1024 Jan 10 23:33 grubenvdrwxr-xr-x. 2 root root 12288 Jan 10 23:32 i386-pcdrwxr-xr-x. 2 root root  4096 Jan 10 23:32 localedrwxr-xr-x. 3 root root  4096 Jan 10 23:28 themes-rw-r--r--. 1 root root     0 May 31 02:13 xxxx


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Re: Possible bug with fsimage/pygrub

[Wei Liu]

On Wed, May 31, 2017 at 06:41:12PM +0000, Ian Murray wrote:
> All,
> Having a very strange problem. I created a CentOS 7 PV vm but could not get pygrub to pick-up the grub entries. I did some fault finding and concluded that `fsimage` was unable to find the grub.cfg.
> I could start the vm as an HVM guest with no problem. I renamed the `grub2` folder to be `grub2.x` and `cp -a` that back to `grub2`. pygrub/fsimage were able to find the file after that. fsimage couldn't see grub2.x/grub.cfg.
> 
>  I wrote small test case in python to illustrate the issue:
> I can only think it is a bug in fsimage, or there is something very hidden about that directory that is causing this.
> Any suggestions would be most welcome,
> Thanks,
> Ian
> import fsimagefs = fsimage.open('/dev/xen2/email', 1048576, "seclabel")if fs.file_exists('/grub2.x/grub.cfg'):  print "found"else:  print "not found"if fs.file_exists('/grub2/grub.cfg'):  print "found"else:  print "not found"
> The results are:-  # python ~/test.py not foundfound
> (mounted locally, after an update, but same behaviour as previously. The partition is on LVM and is formatted ext4)# ls -al grub2*grub2:total 52drwxr-xr-x. 6 root root  4096 May 31 02:39 .dr-xr-xr-x. 7 root root  4096 May 31 02:41 ..-rw-r--r--. 1 root root    86 Jan 10 23:32 device.mapdrwxr-xr-x. 2 root root  4096 Jan 10 23:32 fonts-rw-r--r--. 1 root root  4806 May 31 02:39 grub.cfg-rw-r--r--. 1 root root  4045 Jan 10 23:33 grub.cfg.1496194637.rpmsave-rw-r--r--. 1 root root  1024 May 31 02:39 grubenvdrwxr-xr-x. 2 root root 12288 Jan 10 23:32 i386-pcdrwxr-xr-x. 2 root root  4096 Jan 10 23:32 localedrwxr-xr-x. 3 root root  4096 Jan 10 23:28 themes-rw-r--r--. 1 root root     0 May 31 02:13 xxxx
> grub2.x:total 44drwxr-xr-x. 6 root root  4096 May 31 02:13 .dr-xr-xr-x. 7 root root  4096 May 31 02:41 ..-rw-r--r--. 1 root root    86 Jan 10 23:32 device.mapdrwxr-xr-x. 2 root root  4096 Jan 10 23:32 fonts-rw-r--r--. 1 root root  4045 Jan 10 23:33 grub.cfg-rw-r--r--. 1 root root  1024 Jan 10 23:33 grubenvdrwxr-xr-x. 2 root root 12288 Jan 10 23:32 i386-pcdrwxr-xr-x. 2 root root  4096 Jan 10 23:32 localedrwxr-xr-x. 3 root root  4096 Jan 10 23:28 themes-rw-r--r--. 1 root root     0 May 31 02:13 xxxx
> 

What about extended attributes and other meta data? Maybe they are not
retained after you copied the files?

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