[Pacemaker] DRBD with Pacemaker on CentOs 6.5

Wed Nov 12 01:49:24 CET 2014

Hi,

I'm fluent in English so I doubt it's a language barrier. I have reasonable
user experience in Linux, though not extensive experience in the various
system commands, and I have zero experience in HA. I'm in fact trying to
make things as simple as possible by simply following the "Clusters from
Scratch" guide step by step, and only modifying/omitting steps when they
don't work.

I know a block device (like /dev/sda) is simply a device (such as a hard
disk) that appears like a file in Linux, allowing users buffered access to
the device.
I know a file system is like FAT/NTFS/ext2/etc.
I know a mount point is a directory that you can mount an image file with a
file system onto it. Once mounted, it would be as if the entire file system
has the mount point as its root directory.

I set up DRBD almost exactly like the instructions from Chapter 7 of
"Clusters from Scratch". The only differences are in our setups. The guide
assumes Fedora 13, DRBD 8.3 while I'm using CentOS 6.5 and DRBD 8.4.

Since I was following the guide from start to finish, /var/www/html already
has index.html already in there. node01 has it's own index.html, and node02
has its own index.html, both with different content. The guide did not
instruct me to delete these files, and seems to configure the mount point
to be /var/www/html (Chapter 7.4) with an ext4 file system, hence mounting
the image onto a directory that already has files in it. Is this a problem?

On Tue, Nov 11, 2014 at 6:07 PM, Lars Ellenberg <lars.ellenberg at linbit.com>
wrote:

> On Tue, Nov 11, 2014 at 12:27:23PM +0800, Sihan Goi wrote:
> > Hi,
> >
> > DocumentRoot is still set to /var/www/html
> > ls -al /var/www/html shows different things on the 2 nodes
> > node01:
> >
> > total 28
> > drwxr-xr-x. 3 root root  4096 Nov 11 12:25 .
> > drwxr-xr-x. 6 root root  4096 Jul 23 22:18 ..
> > -rw-r--r--. 1 root root    50 Oct 28 18:00 index.html
> > drwx------. 2 root root 16384 Oct 28 17:59 lost+found
> >
> > node02 only has index.html, no lost+found, and it's a different version
> of
> > the file.
>
> I'm unsure if there is just a language barrier,
> or if you just have not enough experience with linux in general,
> or if you try to make things more complicated as they are.
>
> Do you know
>  * what a block device is?
>  * what a file system is?
>  * what a mount point is?
>  * that a mount point may not be empty, even though it typically is?
>  * what it means to mount a file system to a mount point?
>
> Assuming you set up DRBD in a sane way,
> and it is mounted on *one* node (the node where it is Primary),
> then on the *other* node, where it is NOT mounted,
> you will only see the mount point,
> and whatever happens to be in there.
>
> You probably should clear out the contents of that mount point,
> so that you'd have an empty mount point.
>
> Or, if you like, replace it with some "dummy" content
> that clearly shows that this is the mount point,
> and not the file system that is intended to be mounted there.
>
> > Status URL is enabled in both nodes.
>
> As for the "DocumentRoot must be a directory",
> please double check for typos...
>
>
> > On Oct 30, 2014 11:14 AM, "Andrew Beekhof" <andrew at beekhof.net> wrote:
> >
> > >
> > > > On 29 Oct 2014, at 1:01 pm, Sihan Goi <goister at gmail.com> wrote:
> > > >
> > > > Hi,
> > > >
> > > > I've never used crm_report before. I just read the man file and
> > > generated a tarball from 1-2 hours before I reconfigured all the DRBD
> > > related resources. I've put the tarball here -
> > >
> https://www.dropbox.com/s/suj9pttjp403msv/unexplained-apache-failure.tar.bz2?dl=0
> > > >
> > > > Hope you can help figure out what I'm doing wrong. Thanks for the
> help!
> > >
> > > Oct 28 18:13:38 node02 Filesystem(WebFS)[29940]: INFO: Running start
> for
> > > /dev/drbd/by-res/wwwdata on /var/www/html
> > > Oct 28 18:13:39 node02 kernel: EXT4-fs (drbd1): mounted filesystem with
> > > ordered data mode. Opts:
> > > Oct 28 18:13:39 node02 crmd[9870]:   notice: process_lrm_event: LRM
> > > operation WebFS_start_0 (call=164, rc=0, cib-update=298,
> confirmed=true) ok
> > > Oct 28 18:13:39 node02 crmd[9870]:   notice: te_rsc_command: Initiating
> > > action 7: start WebSite_start_0 on node02 (local)
> > > Oct 28 18:13:39 node02 apache(WebSite)[30007]: ERROR: Syntax error on
> line
> > > 292 of /etc/httpd/conf/httpd.conf: DocumentRoot must be a directory
> > >
> > > Is DocumentRoot still set to /var/www/html?
> > > If so, what happens if you run 'ls -al /var/www/html' in a shell?
> > >
> > > Oct 28 18:13:39 node02 apache(WebSite)[30007]: INFO: apache not running
> > > Oct 28 18:13:39 node02 apache(WebSite)[30007]: INFO: waiting for apache
> > > /etc/httpd/conf/httpd.conf to come up
> > >
> > > Did you enable the status url?
> > >
> > >
> http://clusterlabs.org/doc/en-US/Pacemaker/1.1-plugin/html/Clusters_from_Scratch/_enable_the_apache_status_url.html
>
>
> --
> : Lars Ellenberg
> : http://www.LINBIT.com | Your Way to High Availability
> : DRBD, Linux-HA  and  Pacemaker support and consulting
>
> DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
>
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>

-- 
- Goi Sihan
goister at gmail.com
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