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Re: [Libguestfs] [PATCH v2] NEW API: add blkid command to print the attributes of the device

On 12/04/2011 06:51 PM, Richard W.M. Jones wrote:

> On Sun, Dec 04, 2011 at 11:18:37AM +0800, Wanlong Gao wrote:
>> Hi Rich:
>>> ACKed and pushed,
>>> Thanks!
>>> Rich.
>> I saw that you killed the '-p' option because RHEL5 didn't support this,
>> I want to know that which version of blkid you use? or which util-linux?
>> or which RHEL5 updated release?
>> Because in my RHEL5.7GA, the '-i' option isn't supported, either.
> Yup, you're right ...
> For '-p': '-c /dev/null' should be completely equivalent and it's what
> we use in the rest of daemon/blkid.c.  Is there any other benefit to
> using '-p' instead of '-c /dev/null'?

I think no, the '-p' option can also returns the info of 'partition
table type (PTTYPE) and partitions (PART_*). although the cache func
likes '-c'.

> Obviously I didn't test this, which is why I didn't see that the '-i'
> option isn't supported on RHEL 5 ...
>> But does the '-i' option supported on RHEL5.8?
> I'll need to add a test for it.  It seems pretty straightforward just
> comparing the blkid --help output on RHEL 5:
>   $ /sbin/blkid --help
>   /sbin/blkid: invalid option -- -
>   blkid 1.0.0 (12-Feb-2003)
>   usage:	    blkid [-c <file>] [-ghl] [-o format] [-s <tag>] [-t <token>]
>       [-v] [-w <file>] [dev ...]
>       -c	 cache file (default: /etc/blkid/blkid.tab, /dev/null = none)
>       -g	 garbage collect the blkid cache
>       -h	 print this usage message and exit
>       -s	 show specified tag(s) (default show all tags)
>       -t	 find device with a specific token (NAME=value pair)
>       -l	 lookup the the first device with arguments specified by -t
>       -v	 print version and exit
>       -w	 write cache to different file (/dev/null = no write)
>       dev	 specify device(s) to probe (default: all devices)
> versus upstream:
>   $ blkid --help
>   blkid: invalid option -- '-'
>   blkid from util-linux 2.20.1 (libblkid 2.20.0, 19-Oct-2011)
>   Usage:
>   [...]
>    -p          low-level superblocks probing (bypass cache)
>    -i          gather information about I/O limits
> It is sufficient to grep the blkid --help stderr for '-i'.
>> I saw that the latest e2fsprogs also don't support the '-p' and '-i'
>> options, So I'm considering add these options into e2fsprogs, is it
>> needed?
> Which e2fsprogs program do you mean?

The *libblkid* and the command *blkid* (the interface of 'libblkid') is
developed in e2fsprogs(which is the user tools of ext2/3/4fs), but it
seems that the *libblkid* and command *blkid* is separated from the
*e2fsprogs* project and go into the *util-linux* project with the supporting
to others filesystems more well and adding a lot of features like
*partitions* and so on, and the *-p* and *-i* options is supported.

I think using the *-p* and *-i* options to return the low-level of device
status is the very useful features, but it isn't supported on RHEL5,
because the RHEL5 is too old for us.

So, for the future of *libguestfs*, can we add something to separate these disto?
For example we can remove the features like *-p* from RHEL5 but add it to RHEL6 or
some fedora distos?

Can we just FEATURE this distos?
remove the options like *-p* in *blkid* and so on or just split it from the *stable*
release of *libguestfs*, but the I think the later is a patient thing.

Is it time for us to consider for these things now?

> Rich.

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