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NAME | SYNOPSIS | DESCRIPTION | FILES | EXAMPLES | SEE ALSO | COLOPHON |
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tunables.conf(5) File Formats Manual tunables.conf(5)
tunables.conf - tunables configuration file
/etc/tunables.conf
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.
/etc/tunables.conf
/etc/ld.so.cache
Cached copy of tunables.
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
ld.so(8), ldconfig(8)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.19.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2026-09-09. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.19 2026-08-25 tunables.conf(5)
Pages that refer to this page: ldconfig(8)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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