tunables.conf(5)

NAME
tunables.conf - tunables configuration file

SYNOPSIS
/etc/tunables.conf

DESCRIPTION
Tunables are a feature in the GNU C Library that allows application authors and distribution maintainers to alter the runtime library behavior to match their workload.

The file is parsed by ldconfig(8) and the results stored in /etc/ld.so.cache. The resulting data is read when the program starts execution.

Each line in the file /etc/tunables.conf specifies a tunable, a directive, or a filter.

  Tunables
A tunable is specified with a string of the form name=value.

For a list of supported tunables, please consult the glibc manual that corresponds to your installed version of glibc, or run the following command:

    $ ld.so --list-tunables;

  Directives

include path
    The syntax allows lines to start with the keyword include followed by a glob(7) pattern. Files matching that pattern will be processed as if their contents were included at that point.

  Modifiers
Each line may include zero or more keywords or symbols at the beginning, which affect how each tunable affects each processes. The keywords must be separated by whitespace, but the symbols need not be.

overridable
+
    Allow the tunable to be overridden by the GLIBC_TUNABLES environment variable when the process runs (this is the default).

nonoverridable
-
    Do not allow the tunable to be overridden by the environment variable.

onlysecure
@
    The tunable applies only to AT_SECURE processes, such as one started from a set-user-ID program, or one with elevated capabilities.

nonsecure
$
    The tunable applies only to non-AT_SECURE processes (this is the default).

anysecure
*
    The tunable applies to both AT_SECURE and non-AT_SECURE processes.

  Filters
Filters limit the tunables following it. The effects of a filter are terminated by any of the following:

•   The end of the file.
•   The end of an included file.
•   An include directive.
•   A new (possibly empty) filter.

The syntax is:

    [filter:pattern]

proc
    The proc filter limits the following tunables to processes whose name matches the pattern. The pattern may be an absolute path or just the base name.

A filter can also be empty: []. Such a filter has no effects.

FILES

/etc/tunables.conf

/etc/ld.so.cache
    Cached copy of tunables.

EXAMPLES
Example configuration file:

    glibc.malloc.arenas_max=5
    onlysecure glibc.malloc.arenas_max=1
    -glibc.pthread.rseq=1
    [proc:/bin/bad.program]
    -glibc.pthread.rseq=0
    [proc:some.program]
    -glibc.malloc.mmap_threshold=65536

SEE ALSO
ld.so(8), ldconfig(8)