NAME

       ctl - interface for examination and modification of the library’s internal state.

DESCRIPTION

       The  CTL namespace is organized in a tree structure.  Starting from the root, each node can be either in‐
       ternal, containing other elements, or a leaf.  Internal nodes themselves can only contain other nodes and
       cannot be entry points.  There are two types of those nodes: named and indexed.  Named nodes have  string
       identifiers.   Indexed  nodes represent an abstract array index and have an associated string identifier.
       The index itself is provided by the user.  A collection of indexes present on the path of an entry  point
       is provided to the handler functions as name and index pairs.

       Entry  points are the leaves of the CTL namespace structure.  Each entry point can read from the internal
       state, write to the internal state, exec a function or a combination of these operations.

       The entry points are listed in the following format:

       name | r(ead)w(rite)x(ecute) | global/- | read argument type | write argument type | exec argument type |
       config argument type

       A description of pmem_ctl functions can be found on the following  manual  pages:  libpmemblk_ctl_get(3),
       libpmemlog_ctl_get(3), libpmemobj_ctl_get(3)

CTL EXTERNAL CONFIGURATION

       In  addition  to direct function call, each write entry point can also be set using two alternative meth‐
       ods.

       The first method is to load a configuration directly from the  PMEMBLK_CONF/  PMEMLOG_CONF/  PMEMOBJ_CONF
       environment  variable.  A properly formatted ctl config string is a single-line sequence of queries sepa‐
       rated by `;':

              query0;query1;...;queryN

       A single query is constructed from the name of the ctl write entry point and the argument,  separated  by
       `=':

              entry_point=entry_point_argument

       The entry point argument type is defined by the entry point itself, but there are three predefined primi‐
       tives:

              *) integer: represented by a sequence of [0-9] characters that form
                  a single number.
              *) boolean: represented by a single character: y/n/Y/N/0/1, each
                  corresponds to true or false. If the argument contains any
                  trailing characters, they are ignored.
              *) string: a simple sequence of characters.

       There are also complex argument types that are formed from the primitives separated by a `,':

              first_arg,second_arg

       In summary, a full configuration sequence looks like this:

              (first_entry_point)=(arguments, ...);...;(last_entry_point)=(arguments, ...);

       As an example, to set both prefault at_open and at_create variables:

              PMEMBLK_CONF="prefault.at_open=1;prefault.at_create=1"

       The  second  method  of  loading  an  external  configuration  is  to  set  the  PMEMBLK_CONF_FILE/ PMEM‐
       LOG_CONF_FILE/ PMEMOBJ_CONF_FILE environment variable to point to a file that contains a sequence of  ctl
       queries.  The parsing rules are all the same, but the file can also contain white-spaces and comments.

       To  create a comment, simply use `#' anywhere in a line and everything afterwards, until a new line, will
       be ignored.

       An example configuration file:

              #########################
              # My pmemblk configuration
              #########################
              #
              # Global settings:
              prefault. # modify the behavior of pre-faulting
                  at_open = 1; # prefault when the pool is opened

              prefault.
                  at_create = 0; # but don't prefault when it's created

              # Per-pool settings:
              # ...

SEE ALSO

       libpmemblk_ctl_get(3), libpmemlog_ctl_get(3), libpmemobj_ctl_get(3) and <https://pmem.io>