Re: How important is the MBR partition offset of grub-mkrescue ?

[Andrey Borzenkov]

В Sun, 03 Nov 2013 18:16:09 +0100
"Thomas Schmitt" <address@hidden> пишет:

> Hi,
> 
> i believe to have found the udev rules in Debian 6 which
> govern the population of /dev/disk/by-label.
> 
> File
>   /lib/udev/rules.d/60-persistent-storage.rules
> has
>   # probe filesystem metadata of disks
>   KERNEL!="sr*", IMPORT{program}="/sbin/blkid -o udev -p $tempnode"
>   ...
>   ENV{ID_FS_LABEL_ENC}=="?*",     ENV{ID_FS_USAGE}=="filesystem|other", \
>           SYMLINK+="disk/by-label/$env{ID_FS_LABEL_ENC}"
> 
> I understand that if blkid sets variable ID_FS_LABEL_ENC to
> a non-empty value, then this will become the link name in ./by-label.
> The link target is the device that is being examined by the rule.
> 
> From a USB stick with partition start LBA 1, i get:
> 
>   $ /sbin/blkid -o udev -p /dev/sdb 
>   ID_PART_TABLE_TYPE=dos
>   ID_FS_LABEL=epidemic-4.1-b1-1-ts-amd64
>   ID_FS_LABEL_ENC=epidemic-4.1-b1-1-ts-amd64
>   ID_FS_TYPE=iso9660
>   ID_FS_USAGE=filesystem
>   $ /sbin/blkid -o udev -p /dev/sdb1
>   $
> 
> So why the hell does /dev/sdb1 become link target ?
> Its ID_FS_LABEL_ENC must be empty.
> 
> Any idea how to get a verbous log of these decisions ?
> 

I confirm this. The culprit is this rule in 60-persistent-storage.rules:

# for partitions import parent information
ENV{DEVTYPE}=="partition", IMPORT{parent}="ID_*"

I'm not really sure how exactly to fix it. I.e. normally it is assumed
that device is either partitioned or not. Situation when we have
filesystem on a whole disk *and* individual partitions ... not sure.

I'm interested in which information actually needs to be imported from
parent. May be it should be less aggressive.