Questin about device mapper, Debian and devices

Questin about device mapper, Debian and devices

[January Weiner]

Hello,

I am running a server with Debian stable. After a recent automatic
update and an unrelated reboot suddenly I could not mount some of my
hard disks any more. For example,

mount /dev/sda1 /mnt

gave me

mount: /dev/sda1 already mounted or /mnt busy

It took me quite a while to figure out that it is the device mapper
that makes /dev/sda1 busy. For whatever reason, there are now the
files /dev/dm-0, /dev/dm-1 and /dev/dm-2 that correspond to /dev/sda,
/dev/sda1 and /dev/sda2. I assume they have been created by the dev
mapper. The server has been running for ages, has a relatively complex
setup and has been through a number of configurations. However, I
never really used dev mapper.

My questions are as follows:

1) does dev mapper somehow automatically gets hold of my /dev/sda, or
is there a configuration file somewhere (maybe a stale configuration
that got used after the update? I used to have an lvm, but I got rid
of it. Never on purpose used multipath-tools or dm-crypt). My
suspicion is that it is due to multipath, as multipath -l shows

3600d0230006c1c550bdc214a99d0c000dm-0 Transtec,PV610F16R1B
[size=2.7T][features=0][hwhandler=0]
\_ round-robin 0 [prio=0][active]
 \_ 3:0:0:0 sda 8:0   [active][undef]

...but I never told multipath to do that! Running multipath -v 3 -l
shows that there are some disks that are "blacklisted":

cciss!c0d0: blacklisted
cciss!c0d1: blacklisted
dm-0: blacklisted
dm-1: blacklisted
dm-2: blacklisted
fd0: blacklisted
...

Are they blacklisted automatically or is there a way to do it manually?

2) how do I switch off device mapper for /dev/sda*? I just want to use
my plain /dev/sda1 and /dev/sda2. I don't want to change any of my
working configuration, I am happy with what it is now. For now, I have
mounted /dev/dm-1 and /dev/dm-2, but I don't understand them and what
I don't understand I don't want :-). I tried to deinstall dmsetup and
multipath-tools and running /etc/init.d/multipath-tools stop, but
without success.

3) what would be a reason to keep these /dev/dm-* mappings? multipath i/o?

4) next time -- how do I find out what is using /dev/sda1? I only
figured out what is going on by looking at /proc/partitions; no
standard tools that I normally use (fuser, lsof, lsmod etc.) did not
report anything curious.

Best regards,

j.


-- 
---------Dr. January Weiner 3 ---------------------+---------------
Division of Bioinformatics, University of Muenster | Schloßplatz 4
(+49)(251)8321634 | D48149 Münster
http://www.uni-muenster.de/Evolution/ebb/ | Germany

Re: Questin about device mapper, Debian and devices

[malahal]

January Weiner [january@uni-muenster.de] wrote:
> Hello,
> 
> I am running a server with Debian stable. After a recent automatic
> update and an unrelated reboot suddenly I could not mount some of my
> hard disks any more. For example,
> 
> mount /dev/sda1 /mnt
> 
> gave me
> 
> mount: /dev/sda1 already mounted or /mnt busy
> 
> It took me quite a while to figure out that it is the device mapper
> that makes /dev/sda1 busy. For whatever reason, there are now the
> files /dev/dm-0, /dev/dm-1 and /dev/dm-2 that correspond to /dev/sda,
> /dev/sda1 and /dev/sda2. I assume they have been created by the dev
> mapper. The server has been running for ages, has a relatively complex
> setup and has been through a number of configurations. However, I
> never really used dev mapper.
> 
> My questions are as follows:
> 
> 1) does dev mapper somehow automatically gets hold of my /dev/sda, or
> is there a configuration file somewhere (maybe a stale configuration
> that got used after the update? I used to have an lvm, but I got rid
> of it. Never on purpose used multipath-tools or dm-crypt). My
> suspicion is that it is due to multipath, as multipath -l shows
> 
> 3600d0230006c1c550bdc214a99d0c000dm-0 Transtec,PV610F16R1B
> [size=2.7T][features=0][hwhandler=0]
> \_ round-robin 0 [prio=0][active]
>  \_ 3:0:0:0 sda 8:0   [active][undef]
> 
> ...but I never told multipath to do that! Running multipath -v 3 -l
> shows that there are some disks that are "blacklisted":
> 
> cciss!c0d0: blacklisted
> cciss!c0d1: blacklisted
> dm-0: blacklisted
> dm-1: blacklisted
> dm-2: blacklisted
> fd0: blacklisted
> ...
> 
> Are they blacklisted automatically or is there a way to do it manually?

Remove /etc/multipath.conf file if you have. Same file can be used to
blacklist if you want to apply multipath to exclude few devices.

Re: Questin about device mapper, Debian and devices

[January Weiner]

> Remove /etc/multipath.conf file if you have. Same file can be used to
> blacklist if you want to apply multipath to exclude few devices.

There is no such file. Assuming I enter the blacklist, how do I
restart the service so that I no longer have the mapping present? with
/etc/init.d/multipath-tools restart?

j.

-- 
------------ January Weiner 3  ---------------------+---------------
Division of Bioinformatics, University of Muenster  |  Schloßplatz 4
(+49)(251)8321634                                   |  D48149 Münster
http://www.uni-muenster.de/Evolution/ebb/           |  Germany

Re: Questin about device mapper, Debian and devices

[malahal]

I don't use debian, so I don't know what the defaults are.  "multipath
-F" should remove all multipath mappings. You can use "dmsetup
remove_all" command to remove all device-mapper devices.

-Malahal.

January Weiner [january@uni-muenster.de] wrote:
> > Remove /etc/multipath.conf file if you have. Same file can be used to
> > blacklist if you want to apply multipath to exclude few devices.
> 
> There is no such file. Assuming I enter the blacklist, how do I
> restart the service so that I no longer have the mapping present? with
> /etc/init.d/multipath-tools restart?
> 
> j.
> 
> -- 
> ------------ January Weiner 3  ---------------------+---------------
> Division of Bioinformatics, University of Muenster  |  Schlo?platz 4
> (+49)(251)8321634                                   |  D48149 M?nster
> http://www.uni-muenster.de/Evolution/ebb/           |  Germany
> 
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel

Re: Questin about device mapper, Debian and devices

[Guido Günther]

On Mon, Jun 09, 2008 at 12:08:51PM +0200, January Weiner wrote:
> I am running a server with Debian stable. After a recent automatic
> update and an unrelated reboot suddenly I could not mount some of my
> hard disks any more. For example,
The automatic update wouldn't pull in multipath-tools. So you either
installed it directly or pulled it in via a dependency (most people
install it since kpartx isn't split into it's own package in etch).
Have a look /etc/init.d/*multipath*. Disabling these should help.
Cheers,
 -- Guido