xref: /freebsd/share/man/man4/linux.4 (revision 7aa383846770374466b1dcb2cefd71bde9acf463)
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25.\" $FreeBSD$
26.\"
27.Dd February 8, 2010
28.Dt LINUX 4
29.Os
30.Sh NAME
31.Nm linux
32.Nd Linux ABI support
33.Sh SYNOPSIS
34To compile support for this ABI into the kernel,
35place the following line in your
36kernel configuration file:
37.Bd -ragged -offset indent
38.Cd "options COMPAT_LINUX"
39.Ed
40.Pp
41Alternatively, to load the ABI as a
42module at boot time, place the following line in
43.Xr loader.conf 5 :
44.Bd -literal -offset indent
45linux_load="YES"
46.Ed
47.Sh DESCRIPTION
48The
49.Nm
50module provides limited
51Linux ABI (application binary interface) compatibility
52for userland applications.
53The module provides the following significant facilities:
54.Bl -bullet
55.It
56An image activator
57for correctly branded
58.Xr elf 5
59executable images
60.It
61Special signal handling for activated images
62.It
63Linux to native system call translation
64.El
65.Pp
66It is important to note that the Linux ABI support
67it not provided through an emulator.
68Rather, a true (albeit limited) ABI implementation is provided.
69.Pp
70The following
71.Xr sysctl 8
72tunable variables are available:
73.Bl -tag -width compat.linux.oss_version
74.It compat.linux.osname
75Linux kernel operating system name.
76.It compat.linux.osrelease
77Linux kernel operating system release.
78Changing this to something else is discouraged on non-development systems,
79because it may change the way Linux programs work.
80Recent versions of GNU libc are known to use different syscalls depending
81on the value of this sysctl.
82.It compat.linux.oss_version
83Linux Open Sound System version.
84.El
85.Pp
86The
87.Nm
88module can be linked into the kernel statically with the
89.Dv COMPAT_LINUX
90kernel configuration option
91or loaded as required.
92The following command will load the module
93if it is neither linked into the kernel
94nor already loaded as a module:
95.Bd -literal -offset indent
96if ! kldstat -v | grep -E 'linux(aout|elf)' > /dev/null; then
97	kldload linux > /dev/null 2>&1
98fi
99.Ed
100.Pp
101Note that dynamically linked Linux executables
102will require a suitable environment in
103.Pa /compat/linux .
104Specifically, the Linux run-time linker's hints files
105should be correctly initialized.
106For this reason, it is common to execute the following commands
107to prepare the system to correctly run Linux executables:
108.Bd -literal -offset indent
109if [ -x /compat/linux/sbin/ldconfig ]; then
110	/compat/linux/sbin/ldconfig -r /compat/linux
111fi
112.Ed
113.Pp
114For information on loading the
115.Nm
116kernel loadable module automatically on system startup,
117see
118.Xr rc.conf 5 .
119This information applies
120regardless of whether the
121.Nm
122module is statically linked into the kernel
123or loaded as a module.
124.Sh FILES
125.Bl -tag -width /compat/linux/proc -compact
126.It Pa /compat/linux
127minimal Linux run-time environment
128.It Pa /compat/linux/proc
129limited Linux process file system
130.It Pa /compat/linux/sys
131limited Linux system file system
132.El
133.Sh SEE ALSO
134.Xr brandelf 1 ,
135.Xr elf 5 ,
136.Xr linprocfs 5 ,
137.Xr linsysfs 5
138.Sh HISTORY
139Linux ABI support first appeared in
140.Fx 2.1 .
141