---
name: "tunables.conf"
section: "5"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/tunables.conf"
---

# tunables.conf(5)

tunables configuration file

## 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)](/ldconfig/8.md) 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)](/glob/7.md) 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)](/ld.so/8.md), [**ldconfig**(8)](/ldconfig/8.md)