usr.sbin/sysconf/sysconf.8

.\" Copyright (c) 2013-2026 Devin Teske <dteske@FreeBSD.org>
.\" Copyright (c) 2021-2026 Faraz Vahedi <kfv@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd September 16, 2026
.Dt SYSCONF 8
.Os
.Sh NAME
.Nm sysconf
.Nd read and modify system configuration files
.Sh SYNOPSIS
.Nm
.Ar target
.Op Fl AcDeFinNqsvVx
.Op Fl j Ar jail | Fl R Ar dir
.Op Fl f Ar file | Fl k Ar module
.Ar name Ns Op Ns Oo +|- Oc Ns = Ns Ar value
.Ar ...
.Nm
.Ar target
.Op Fl ADeFnNqvV
.Op Fl j Ar jail | Fl R Ar dir
.Op Fl f Ar file | Fl k Ar module
.Fl a
.Nm
.Ar target
.Op Fl AaDinNq
.Op Fl j Ar jail | Fl R Ar dir
.Fl d
.Op Ar name ...
.Nm
.Ar target
.Op Fl E
.Op Fl j Ar jail | Fl R Ar dir
.Op Fl k Ar module
.Fl l | L
.Nm
.Cm rc
.Op Ar sysrc_argument ...
.Sh DESCRIPTION
The
.Nm
utility reads and modifies the system configuration files of the base
system,
completing the native configuration trinity alongside
.Xr sysctl 8
.Pq kernel state
and
.Xr sysrc 8
.Pq Xr rc.conf 5 .
The first positional argument selects a
.Ar target
keyword;
options are equally accepted before it.
Each target is documented on its own page
.Pq see Sx TARGETS ;
shared options and assignment syntax are documented here.
.Ss Assignment syntax
A
.Ar name
alone reads the current value of the directive,
while
.Ar name Ns = Ns Ar value
atomically writes it.
Writes echo
.Ql name: old -> new
when the stored value changes,
or
.Ql name: value (unchanged)
when it is already set as requested
.Pq the file is left untouched in that case .
With
.Fl e
those echoes use
.Ql name=...
instead of
.Ql name: ...
.Pq matching read output .
The echo is suppressed by
.Fl q ;
.Fl c
writes nothing to stdout.
A directive not previously set anywhere shows an empty old value.
.Pp
On the
.Cm make
and
.Cm src
targets, a
.Ql WITH_*
or
.Ql WITHOUT_*
build knob
.Pq presence matters; Xr src.conf 5 ignores the value
is shown as
.Ql name (present)
when defined
.Po
any value, including
.Ql =
or
.Ql =t
.Pc ,
rather than printing the value after the colon;
.Fl e
prints the real assignment
.Po
e.g.
.Ql name=
or
.Ql name=t
.Pc ,
and
.Fl n
prints that same value alone
.Pq empty when the assignment is Ql name= .
Setting such a knob with
.Fl s
echoes
.Ql name: (not present) -> (present)
.Po
or
.Ql (present) (unchanged)
when it is already defined
.Pc .
An explicit
.Ar name Ns =
.Pq including empty
always writes the requested value;
a change of placeholder while the knob stays defined echoes
.Ql name: old -> new
like other assignments.
A write of
.Ql WITH_ Ns Ar foo Ns =no
.Pq exact lowercase Ql no
is still performed but warns to use
.Ql WITHOUT_ Ns Ar foo Ns =1
instead.
That message matches
.Pa share/mk/bsd.mkopt.mk
and is emitted here as a precursor so a bad
.Xr make.conf 5
or
.Xr src.conf 5
assignment is caught at write time.
The same advisory is printed on reads
.Po
named queries and
.Fl a
dump
.Pc ,
with
.Ql file:line:
when the authoritative statement is known, so an existing
.Ql WITH_* Ns =no
is not overlooked when presence display shows only
.Ql (present) .
.Fl q
suppresses the read-time form.
.Xr make 1
itself typically warns later during a
.Pa /usr/src
build, when
.Pa bsd.opts.mk
.Pq or Pa src.opts.mk
reloads
.Pa bsd.mkopt.mk
for recognized options such as
.Va MANCOMPRESS .
The same
.Xr make.conf 5
line stays silent for a bare
.Xr make 1
.Pq e.g. Fl C Pa /tmp
or for ports, which do not run that option pass.
.Ql WITHOUT_* Ns =no ,
.Ql WITH_* Ns =NO ,
and other values do not warn here or there.
.Va WITHOUT_MODULES
is not a presence knob
.Pq its value is a module list
and is excluded from
.Fl s
and presence display.
.Pp
For directives whose value is a space-separated list
.Po
.Va kld_list Ns -style ;
see for example
.Va kernels
in
.Xr loader.conf 5
.Pc ,
.Ar name Ns += Ns Ar word
appends each given word not already present and
.Ar name Ns -= Ns Ar word
strikes each given word,
after the fashion of
.Xr sysrc 8 .
Striking words from a directive set nowhere is reported like any other
unknown directive.
.Pp
For
.Xr make 1 Ns -syntax
targets
.Po
.Cm make
and
.Cm src ;
see
.Xr sysconf-make 8
and
.Xr sysconf-src 8
.Pc ,
.Ql +=
is instead the
.Xr make 1
append operator and
.Ql -=
strikes words from the last matching assignment fragment.
.Pp
Files are never modified in place:
updates are streamed to a temporary file which is flushed to stable storage
and atomically renamed over the target
.Pq see Xr bsdconf_put 3 .
How multi-file targets choose the file to read or rewrite is documented in
.Xr sysconf-targets 8 .
.Sh TARGETS
The following target keywords are supported:
.Bl -tag -width indent
.It Cm loader
Boot loader configuration
.Pq Xr loader.conf 5 .
See
.Xr sysconf-loader 8 .
.It Cm sysctl
Kernel state set at boot
.Pq Xr sysctl.conf 5 .
See
.Xr sysconf-sysctl 8 .
.It Cm make
System-wide
.Xr make 1
settings
.Pq Pa /etc/make.conf .
See
.Xr sysconf-make 8 .
.It Cm src
The
.Pa /usr/src
build triad
.Pq Pa src-env.conf , make.conf , src.conf .
See
.Xr sysconf-src 8 .
.It Cm rc
Pass-through to
.Xr sysrc 8 .
See
.Xr sysconf-rc 8 .
.It Cm generic
Foreign or unknown format;
requires
.Fl f .
See
.Xr sysconf-generic 8 .
.El
.Pp
Cross-cutting rules for multi-file sourcing,
defaults,
and where writes versus removals land are in
.Xr sysconf-targets 8 .
Built-in format descriptors and file-list discovery are in
.Xr bsdconf_format 3 .
.Sh OPTIONS
The options are as follows:
.Bl -tag -width indent
.It Fl A
Widen dump scope to include directives still at their system default
.Po
named reads always reflect the defaults;
see
.Xr sysconf-targets 8
.Pc .
With no
.Ar name
arguments,
dumps everything
.Po
as
.Fl a ,
defaults included
.Pc .
.Pp
Combined with
.Fl D ,
the scoping of
.Fl D
wins and
.Fl A
retains only its dump-implying role,
so
.Ql -ADd
describes all defaults and only defaults,
as in
.Xr sysrc 8 .
Only valid for targets with a defaults file
.Pq see Xr sysconf-loader 8 .
.It Fl a
Dump all configured directives from the target:
the union of the target's files,
wherein directives in later files override earlier ones.
Directives whose value still comes from the defaults file alone are out
of scope
.Pq widen with Fl A .
.It Fl c
Check mode.
For each
.Ar name Ns = Ns Ar value
argument,
compare the effective value against
.Ar value
without modifying any file
.Po
with
.Fl x ,
check that
.Ar name
is absent
.Pc .
Exit with success if no changes would be required,
else error.
.It Fl D
Consult only the target's defaults file,
reporting the system default value of each
.Ar name
.Po
or, with
.Fl a ,
dumping every default
.Pc .
Defaults are read-only;
combining
.Fl D
with an assignment is an error.
Only valid for targets with a defaults file
.Pq see Xr sysconf-loader 8 .
.It Fl d
Show the description of each
.Ar name
instead of its value.
.Pp
For targets with a defaults file,
the description is the inline comment trailing the directive's default
assignment,
continued across subsequent lines of whitespace followed by a comment
character.
A commented-out default
.Pq e.g., Ql #comconsole_speed=\(dq115200\(dq # Set the ...
still yields its description.
For the
.Ql sysctl
target,
descriptions come from the running kernel
.Po
as with
.Xr sysctl 8
.Fl d ;
see
.Xr sysconf-sysctl 8
.Pc .
.Pp
Combined with
.Fl a ,
.Fl A ,
or
.Fl D ,
dumps the description of every directive in scope
.Po
of the configured directives,
of everything defaults included,
or of the defaults alone,
respectively
.Pc ,
after the fashion of
.Xr sysrc 8
.Fl \&Ad .
A directive the defaults never mention prints an empty description.
.It Fl E
With
.Fl l
or
.Fl L ,
list only files that exist on disk.
.It Fl e
Print values in
.Ar name Ns = Ns Ar value
format,
suitable for feeding back into the configuration file.
Applies to both reads and the informational echo from assignments
.Po
replacing the default
.Ql name: value
form;
changed writes use
.Ql name=old # -> new ,
matching
.Xr sysrc 8
.Pc .
For the
.Ql loader
target the value is quoted.
.It Fl F
Show the pathname of the file holding each directive's effective
.Pq authoritative
value instead of the value itself.
For a directive still at its system default,
this truthfully names the defaults file.
.It Fl f Ar file
Operate on
.Ar file ,
in the format of the
.Ar target
keyword,
instead of the target's standard files;
mutually exclusive with
.Fl k .
For read operations
.Ar file
may be a non-seekable stream
.Po
a fifo or
.Pa /dev/stdin ,
for example
.Pc ;
write operations require a regular file.
A
.Ar file
of
.Ql -
means standard input
.Pq a synonym for Pa /dev/stdin ,
exempt from
.Fl R .
See
.Xr sysconf-targets 8
and
.Xr sysconf-generic 8 .
.It Fl h , Fl Fl help
Print a short usage statement
.Pq or, for the long form, the full option summary
to stderr and exit.
.It Fl Fl version
Print
.Nm
and linked
.Xr bsdconf 3
versions and exit.
.It Fl i
Ignore unknown names
.Pq and suppress the warning when writing an unknown sysctl OID .
.It Fl j Ar jail
Operate within the jail
.Ar jail
.Pq name or numeric id ;
mutually exclusive with
.Fl R .
.It Fl k Ar module
Include the kernel module drop-in file for
.Ar module
in the target's file list
.Pq e.g., Pa /etc/sysctl.kld.d/ Ns Ar module Ns Pa .conf .
Only valid for targets with a module drop-in directory
.Pq see Xr sysconf-sysctl 8 .
.It Fl l
List the pathnames of the files backing the target,
in sourcing order,
and exit.
The read-only defaults file is never listed
.Po
.Fl l
enumerates only files
.Nm sysconf
may modify;
see
.Xr sysconf-targets 8
.Pc .
.It Fl L
Like
.Fl l ,
but additionally list every drop-in candidate:
for targets with a module drop-in directory,
one candidate per loaded kernel module
.Pq whether or not the file exists yet
plus any drop-in already on disk.
The read-only defaults file is likewise never listed.
.It Fl n
Show only directive values,
not their names.
.It Fl N
Show only directive names,
not their values.
.It Fl q
Quiet.
Suppress warnings about unknown directives and the
.Ql old -> new
echo of write operations.
.It Fl R Ar dir
Operate within the root directory
.Ar dir
rather than
.Pa / ;
mutually exclusive with
.Fl j .
.It Fl s
Set empty
.Ql WITH_*
and
.Ql WITHOUT_*
build knobs on the
.Cm make
and
.Cm src
targets
.Po
equivalent to
.Ar name Ns =
with no value;
see
.Xr sysconf-make 8
and
.Xr sysconf-src 8
.Pc .
Each bare
.Ar name
must begin with
.Ql WITH_
or
.Ql WITHOUT_ .
An already-present knob
.Pq any value
is left unchanged by
.Fl s .
An explicit
.Ar name Ns =
including empty always writes.
Mutually exclusive with
.Fl x .
.It Fl v
Verbose.
Print the pathname of the configuration file holding the final effective
value
.Pq the last file in sourcing order that assigned the directive .
.It Fl V
Trail.
For each named read
.Pq and for Fl a ,
print every assignment step that contributed to the effective value:
.Ql file:line: nameopfragment ,
and when the running effective value differs from the fragment,
.Ql -> effective .
.Pp
For writes, print the same
.Ql file:line:
shape for the change:
.Ql file:line: name=old -> name=new ,
.Ql name=value (unchanged) ,
.Ql name=value (added)
when a new statement is created,
or
.Ql nameopfragment (removed)
when a statement is deleted,
using the statement operator
.Ql = / += / ...
as appropriate .
.Pp
Uses the same accumulation model as ordinary reads
.Pq make(1) `+=' et al. ,
so the last effective value matches
.Fl v
and,
for linear conf files without
.Ql .if ,
.Nm make Fl V
.Pq see Xr sysconf-make 8 and Xr sysconf-src 8 .
.It Fl x
Remove the named directive(s) from every file of the target listing them
.Pq see Xr sysconf-targets 8 .
With
.Fl v
or
.Fl V ,
a successful removal echoes
.Ql name (removed)
.Pq or a trail form with Fl V .
.El
.Sh ENVIRONMENT
.Bl -tag -width "LOADER_DEFAULTS"
.It Ev BSDCONF_MAX_BYTES
Maximum bytes
.Nm
will read from a configuration file or stream;
see
.Xr bsdconf 3 .
.It Ev LOADER_DEFAULTS
Defaults file for the
.Ql loader
target;
see
.Xr sysconf-loader 8 .
.It Ev SRC_ENV_CONF , Ev __MAKE_CONF , Ev SRCCONF
Paths for the
.Cm src
triad;
see
.Xr sysconf-src 8 .
.El
.Sh FILES
See the per-target manuals
.Pq Xr sysconf-loader 8 , Xr sysconf-sysctl 8 , Xr sysconf-make 8 , Xr sysconf-src 8
for the files each keyword consults.
Common paths include
.Pa /boot/loader.conf ,
.Pa /etc/sysctl.conf ,
.Pa /etc/make.conf ,
and
.Pa /etc/src.conf .
.Sh EXIT STATUS
.Ex -std
In check mode
.Pq Fl c ,
an exit status of zero means no changes are required.
.Sh EXAMPLES
Read and set a boot loader directive:
.Pp
.Dl sysconf loader zfs_load
.Dl sysconf loader zfs_load=\(dqYES\(dq
.Pp
Raise a sysctl applied at boot:
.Pp
.Dl sysconf sysctl kern.maxfiles=65536
.Pp
List files backing the loader target:
.Pp
.Dl sysconf loader -l
.Pp
Append to a space-separated list:
.Pp
.Dl sysconf loader kernels+=kernel_test
.Pp
Append a
.Xr make 1
flag and set a
.Pa src.conf
knob:
.Pp
.Dl sysconf make CFLAGS+=-DDEBUG
.Dl sysconf src -s WITHOUT_LLDB
.Dl sysconf src WITHOUT_LLDB=
.Pp
Further examples for each target appear in
.Xr sysconf-loader 8 ,
.Xr sysconf-sysctl 8 ,
.Xr sysconf-make 8 ,
.Xr sysconf-src 8 ,
.Xr sysconf-rc 8 ,
and
.Xr sysconf-generic 8 .
.Sh SEE ALSO
.Xr bsdconf 3 ,
.Xr bsdconf_format 3 ,
.Xr bsdconf_put 3 ,
.Xr loader.conf 5 ,
.Xr src.conf 5 ,
.Xr sysctl.conf 5 ,
.Xr jail 8 ,
.Xr sysconf-generic 8 ,
.Xr sysconf-loader 8 ,
.Xr sysconf-make 8 ,
.Xr sysconf-rc 8 ,
.Xr sysconf-src 8 ,
.Xr sysconf-sysctl 8 ,
.Xr sysconf-targets 8 ,
.Xr sysctl 8 ,
.Xr sysrc 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 16.0 .
.Sh AUTHORS
.An Devin Teske Aq Mt dteske@FreeBSD.org
.An Faraz Vahedi Aq Mt kfv@FreeBSD.org
.Sh SECURITY CONSIDERATIONS
Read-only invocations
.Po
including
.Fl c
checks, which never modify files
.Pc
run inside a
.Xr capsicum 4
sandbox:
the backing files are opened first and the process then relinquishes all
other capabilities before any file content is parsed.
.Pp
Write operations replace files atomically and never in place;
see the
.Sx SECURITY CONSIDERATIONS
section of
.Xr bsdconf_put 3
for the properties of the write transaction.