[DRBD-user] early steps: block device creation? (done during os install only?)

Karl R. Balsmeier karl at clickability.com
Fri Jun 22 20:15:06 CEST 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Am I supposed to make the block device during the initial server 
build/OS install, -like creating /drbd at 130M on say /dev/sda8?

If so, any specific steps, e.g. not giving it a mount point, or?

-it would look like this right?:

[root at ftp04 ~]# df
Filesystem           1K-blocks      Used        Available   Use%   
Mounted on
/dev/sda5              5952252    561064      5083948  10%        /
/dev/sda1               497829     25517           446610   6%         /boot
tmpfs                    2029856         0             2029856   
0%         /dev/shm
/dev/sda6              1984016     35876       1845728   2%         /tmp
/dev/sda3              5952284   2704752     2940292  48%       /usr
/dev/sda7             79839696    317484   75401140   1%        /var
<dedicated space for a block device to be named in my drbd.conf>
/dev/sda8             131073    131072            131072   1%        /drbd

If so, after booting do I then umount it, add it to my 'disk' directive 
in drbd.conf and re-run drbdadm up all?

umount -f  /drbd  [??]   -will this even work?  won't I get: umount: 
/drbd: device is busy  [??]

Right now when I try to run drbdadm up all on the existing box I get:

[root at ftp04 ~]# drbdadm up all
Failure: (114) Lower device is already claimed. This usually means it is 
Command 'drbdsetup /dev/drbd1 disk /dev/sda7 /dev/sda7 internal 
--set-defaults --create-device' terminated with exit code 10

and my drbd.conf looks like this: 

(/dev/sda7 being my /var directory  -which is just plain wrong, -it 
should be a drbd dedicated volume not being used by any part of the OS 

global { usage-count yes; }
       common { syncer { rate 10M; } }
       resource r0 {
            protocol C;
            net {
                 cram-hmac-alg sha1;
                 shared-secret "secretphrase";
            on mybox1.mydomain.com {
                 device    /dev/drbd1;
                 disk      /dev/sda7;
                 meta-disk  internal;
            on mybox2.mydomain.com {
                 device    /dev/drbd1;
                 disk      /dev/sda7;
                 meta-disk  internal;

 -is there some fdisk action that I could perform that would borrow the 
128 Megs from an existing partition so I don't have to do an OS re-install?

Any advice at all would be appreciated.  I picked up on the drbd howto's 
directions after I had a few servers already with centos5 on board, so 
if it's just a matter of a reinstall and some follow-up steps to get 
toward a working setup I think the remaining instructions are clear 
enough.  My ultimate intent is to use these as vsftpd servers running 
drbd and heartbeat2.


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