Ubuntu Manpage: drbdlinks - manages links into a shared DRBD partition

NAME

       drbdlinks - manages links into a shared DRBD partition

SYNOPSIS

       drbdlinks [OPTION]... [start|stop|auto|status|monitor|checklinks]

DESCRIPTION

drbdlinks is a program that will manage creation and removal of symbolic links. It is
primarily used with clusters of machines using either shared storage or the "DRBD"
replicated block device.

While the name of the program is "drbdlinks", it can be used in any shared-storage sort of
environment where the shared storage is only mounted on the active node. In cases like
NFS where the shared storage is always mounted on all nodes, drbdlinks is not necessary.

The advantage over creating static symbolic links is that package updates often require
that directories point at real files, so updates can often fail if you do not have the
shared storage mounted.

drbdlinks also supports multiple instances of links, in the case of active/active
clusters. For example, if you have MySQL running in one resource group, and Apache
running in another, you can use the "-c" switch to specify a configuration file for each
resource group.

A simple configuration file, "/etc/drbdlinks.conf", specifies the links. This can be used
to manage links for /etc/httpd, /var/lib/pgsql, and other system directories that need to
appear as if they are local to the system when running applications after a drbd shared
partition has been mounted.

When run with "start" as the mode, drbdlinks will rename the existing files/directories,
and then make symbolic links into the DRBD partition. "stop" does the reverse.

Mode "checklinks" will report any links that do not exist in the destination area. During
initial setup and configuration, this can help check that you have the destination file-
system set up with the required components.

If run with "initialize_shared_storage", destination links specified in the configuration
file will be populated from the source storage. This is useful for initial setup to
populate the shared storage. Preceding paths will be populated if they share the same
name from source to destination.

The "monitor" and "status" modes will check the file-system against the configuration file
and will report "running" (monitor mode) or "OK" (status mode) if all links appear to be
up. Otherwise they report "down" or "stopped" (respectively).

By default, the rename appends .drbdlinks to the name, but this can be overridden in the
configuration file.

The "list" mode just show the list of links, with each line showing the link, destination,
and a 0/1 flag for bindMount status. This may be useful for user scripts without having
to parse the configuration.

An init script is included which runs "stop" before heartbeat starts, and after heartbeat
stops. This is done to try to ensure that when the shared partition isn't mounted, the
links are in their normal state.

OPTIONS

       drbdlinks has several options, using either short or long variants.

       -h, --help
              Print a short help message describing the available options and exit.

       -c, --config-file=CONFIGFILE
              Specify an alternate config file.  The default config file is  /etc/drbdlinks.conf.
              Alternate  config  files  should  have  a  "drbdlinks-"  prefix,  e.g.  "drbdlinks-
              httpd.conf".

       -s, --suffix=SUFFIX
              Name to append to the local file-system name  when  the  link  is  in  place.   The
              default   is   "drbdlinks",   which   would   result   in   a   renamed  file  like
              "/etc/httpd.drbdlinks".

       -v, --verbose
              Increase verbosity level by 1 for every occurrence of this option.

EXAMPLES

       Here are a few examples of how drbdlinks can be used.

       The most straight-forward, and default, method for starting drbdlinks:

              drbdlinks start

       To use a suffix different from the default when linking to a file  or  directory,  the  -s
       option can be used, specifying the desired string:

              drbdlinks -s orig start

       would rename the file-system name to "name.orig".

       Increase the verbosity to assist in debugging:

              drbdlinks -v -v start

       Use an alternate configuration file, possibly from with a DRBD mounted file-system:

              drbdlinks -c /shared1/drbdlinks-httpd.conf start

       This  would  use  the  specified  configuration  file, found on our DRBD device mounted on
       /shared1.  This would allow us to easily keep drbdlinks configurations tied to a  specific
       set of data on a DRBD disk in an active/active sort of HA configuration.

AUTHOR