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Mon, 03 Aug 2026 15:21:39 -0400 X-MC-Unique: 35LocJMcNpawct38xVFmVQ-1 X-Mimecast-MFC-AGG-ID: 35LocJMcNpawct38xVFmVQ_1785784898 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 53E9B180034A; Mon, 3 Aug 2026 19:21:38 +0000 (UTC) Received: from greed.delorie.com (unknown [10.22.88.221]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 08EC7195608E; Mon, 3 Aug 2026 19:21:37 +0000 (UTC) Received: from greed.delorie.com.redhat.com (localhost [127.0.0.1]) by greed.delorie.com (8.16.1/8.16.1) with ESMTP id 673JLV2p3318293; Mon, 3 Aug 2026 15:21:31 -0400 From: DJ Delorie To: Alejandro Colomar Cc: linux-man@vger.kernel.org Subject: [PATCH v4 2/4] man/man5/tunables.conf: Document system-wide tunables config Date: Mon, 03 Aug 2026 15:21:31 -0400 Message-ID: Precedence: bulk X-Mailing-List: linux-man@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Signed-off-by: DJ Delorie --- man/man5/tunables.conf.5 | 132 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 132 insertions(+) create mode 100644 man/man5/tunables.conf.5 diff --git a/man/man5/tunables.conf.5 b/man/man5/tunables.conf.5 new file mode 100644 index 000000000..44b32d40c --- /dev/null +++ b/man/man5/tunables.conf.5 @@ -0,0 +1,132 @@ +.TH tunables.conf 5 (date) "Linux man-pages (unreleased)" +.SH NAME +tunables.conf \- tunables configuration file +.SH SYNOPSIS +.nf +.B /etc/tunables.conf +.fi +.SH 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. +For a list of supported tunables, +please consult the glibc manual +that corresponds to your installed version of glibc, +or run the following command: +.P +.in +4n +.EX +ld.so \-\-list\-tunables +.EE +.P +The file is parsed by +.BR \%ldconfig (8) +and the results stored in +.IR /etc/ld.so.cache . +The resulting data is read when a new process is created by +.IR ld.so . +.P +Each line in the file +.I /etc/tunables.conf +specifies a tunable, +which is specified with a string of the form +.IB name = value \f[R].\f[] +.P +The syntax allows lines to start with the keyword +.I include +followed by a +.BR \%glob (7) +pattern. +Files matching that pattern will be processed +as if their contents were included at that point. +.P +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. +.TP +.B overridable +.TQ +.B + +Allow the tunable to be overridden by the +.B GLIBC_TUNABLES +environment variable when the process runs +(this is the default). +.TP +.B nonoverridable +.TQ +.B \- +Do not allow the tunable to be overridden by the environment variable. +.TP +.B onlysecure +.TQ +.B @ +The tunable applies only to +.B AT_SECURE +processes, +such as one started from a set-user-ID program, +or one with elevated capabilities. +.TP +.B nonsecure +.TQ +.B $ +The tunable applies only to +.RB non- AT_SECURE +processes (this is the default). +.TP +.B anysecure +.TQ +.B * +The tunable applies to both +.B AT_SECURE +and +.RB non- AT_SECURE +processes. +.P +The file may also contain +.IR filters , +which limit the tunables following it, +up to the end of the file +(or end of the included file, +or start of a new included file) +or a line with only +.B [] +on it. +The syntax is: +.P +.in +4n +.EX +.RI [ filter : pattern ] +.EE +.in +.TP +.B proc +The +.B 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. +.SH FILES +.TP +.I /etc/tunables.conf +.TP +.I /etc/ld.so.cache +cached copy of tunables +.SH EXAMPLES +Example configuration file: +.P +.in +4n +.EX +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 +.EE +.in +.SH SEE ALSO +.BR ld.so (8), +.BR ldconfig (8) -- 2.47.3