Paul Bijnens wrote:

Following up on myself... (as usual on mondays)...

And again following up on myself...  ;-)

Paul Bijnens wrote:

The good news is that Redhat just fixed this very recently.
in device-mapper-1.01.01-1.RHEL4, which you can install by up2date
or "yum update device-mapper".

https://rhn.redhat.com/errata/RHEA-2005-188.html  says:

 > [...]
 > - The inodes created in the /dev/mapper directory when devices are
 > activated are now accessible by the 'disk' group used by some
 > backup tools.

The bad news is that I just rebooted a Centos 4 under VMWare to test
it,  with this patch installed, and the permissions are still bad.

brw-------  1 root root 253,  0 Jun 20  2005 /dev/mapper/VolGroup00-LogRoot

Maybe the news is not as bad neither.

Suddenly I noticed that when I make a snapshot of a logical volume
the permission ARE indeed correct:

$ cd /dev/mapper
$ ls -l *pace*
brw-------  1 root root 253, 1 Jun 20 19:00 VolGroup00-LogSpace
brw-rw----  1 root disk 253, 6 Jun 22 17:25 VolGroup00-LogSpace-real

The script that makes these snapshots is already in use some months now
and I never really looked into the files it created in /dev/mapper/ either.
It's only now that I notice that creating a snapshot, also creates
a *-real and a *-cow file.  A quick google does not get me any info
about the meaning of those files either.


The script creates a snapshot with a variable name, including
the data-time in the name, making it more selfdocumenting.

For my backups, I mount those snapshots in the /snap directory:

  mount -o ro /dev/VolGroup00/_space-...snap /snap/_space-...snap

create a simple symlink to it, so that I can use that fixed name
in the disklist in amanda:

  ln -s /snap/_space-2005-06-22-17.25.snap /snap/_space

and with amanda I make gnutar backups of them with this DLE:

  the.host.com  /space  /snap/_space  comp-user-tar 1

The snapshots stay mounted for the rest of the day, so that
people can restore files from the previous day, without using amanda
(and my help to insert the tape).

I never tried to use dump instead of gnutar on the snapshotdevices,
but I guess it should work out fine.
At least the permissions are OK there.

Because I do not have an older system without the update mentioned
above, I can't verify if these permissions settings are new or not.

Attached is the script that I use to manage the snapshots.
You can base your config on this. (Any feedback on the script
itself is welcome too.)
Crontab runs this 1 minute past midnight as root.  And amanda starts
5 minutes past midnight.


--
Paul Bijnens, Xplanation                            Tel  +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM    Fax  +32 16 397.512
http://www.xplanation.com/          email:  Paul.Bijnens AT xplanation DOT com
***********************************************************************
* I think I've got the hang of it now:  exit, ^D, ^C, ^\, ^Z, ^Q, F6, *
* quit,  ZZ, :q, :q!,  M-Z, ^X^C,  logoff, logout, close, bye,  /bye, *
* stop, end, F3, ~., ^]c, +++ ATH, disconnect, halt,  abort,  hangup, *
* PF4, F20, ^X^X, :D::D, KJOB, F14-f-e, F8-e,  kill -1 $$,  shutdown, *
* init 0, kill -9 1, Alt-F4, Ctrl-Alt-Del, AltGr-NumLock, Stop-A, ... *
* ...  "Are you sure?"  ...   YES   ...   Phew ...   I'm out          *
***********************************************************************

#!/bin/sh

# Create a snapshot for the amanda backups

USAGE="$0 [-r] [-n] [-s 1g]"
REMOVEONLY=
DONOTREMOVE=
SIZE=1g

while getopts nrs: i
do
    case $i in
        n) DONOTREMOVE=donotremove;;
        r) REMOVEONLY=removeonly;;
        s) SIZE=$OPTARG ;;
        \?) echo $USAGE
                exit 2 ;;
    esac
done
shift `expr $OPTIND - 1`

PATH=/sbin:/bin:$PATH; export PATH

lvs --noheadings --options vg_name,lv_name,origin --sort -origin |
while read vg_name lv_name origin
do
    lv__name=`echo $lv_name | sed -e 's/-/--/g'`
    mountpoint=`mount | grep "$vg_name-$lv__name" | sed -e 's/.* on //' -e 's/ 
type .*//'`
    case $mountpoint in
        /)    continue ;;       # snapshots for root fs are not working (??)
        /tmp) continue ;;       # neither for /tmp
        "")   continue ;;       # e.g. swap
    esac

    if [ -n "$origin" -a -z "$DONOTREMOVE" ]
    then
        if test -e /dev/$vg_name/$lv_name
        then umount /dev/$vg_name/$lv_name
        fi
        rmdir /snap/$lv_name
        lvremove -f /dev/$vg_name/$lv_name >/dev/null  ||  {
            echo Remove Snapshot $SNAPNAME error
            exit 1
        }
        continue
    fi
    if [ -n "$origin"  -o  -n "$REMOVEONLY" ]
    then continue
    fi

    mountpoint=`echo $mountpoint | tr '/' '_'`
    SNAPNAME=$mountpoint-`date +%Y-%m-%d-%H.%M`.snap
    lvcreate --snapshot --size $SIZE --name $SNAPNAME \
                /dev/$vg_name/$lv_name  >/dev/null  ||  {
            echo Create Snapshot $SNAPNAME error
            exit 1
        }
    SNAPDIR=/snap/$SNAPNAME
    mkdir $SNAPDIR

    rm -f /snap/$mountpoint
    ln -s /snap/$SNAPNAME /snap/$mountpoint        # symlink for Amanda

    mount -o ro /dev/$vg_name/$SNAPNAME $SNAPDIR

done