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selinux(8) SELinux Command Line documentation selinux(8)
NAME
SELinux - NSA Security-Enhanced Linux (SELinux)
DESCRIPTION
NSA Security-Enhanced Linux (SELinux) is an implementation of a flexible mandatory access
control architecture in the Linux operating system. The SELinux architecture provides
general support for the enforcement of many kinds of mandatory access control policies,
including those based on the concepts of Type Enforcement(R), Role- Based Access Control,
and Multi-Level Security. Background information and technical documentation about
SELinux can be found at http://www.nsa.gov/research/selinux.
The /etc/selinux/config configuration file controls whether SELinux is enabled or dis-
abled, and if enabled, whether SELinux operates in permissive mode or enforcing mode. The
SELINUX variable may be set to any one of disabled, permissive, or enforcing to select one
of these options. The disabled option completely disables the SELinux kernel and applica-
tion code, leaving the system running without any SELinux protection. The permissive
option enables the SELinux code, but causes it to operate in a mode where accesses that
would be denied by policy are permitted but audited. The enforcing option enables the
SELinux code and causes it to enforce access denials as well as auditing them. Permissive
mode may yield a different set of denials than enforcing mode, both because enforcing mode
will prevent an operation from proceeding past the first denial and because some applica-
tion code will fall back to a less privileged mode of operation if denied access.
The /etc/selinux/config configuration file also controls what policy is active on the sys-
tem. SELinux allows for multiple policies to be installed on the system, but only one
policy may be active at any given time. At present, multiple kinds of SELinux policy
exist: targeted, mls for example. The targeted policy is designed as a policy where most
user processes operate without restrictions, and only specific services are placed into
distinct security domains that are confined by the policy. For example, the user would
run in a completely unconfined domain while the named daemon or apache daemon would run in
a specific domain tailored to its operation. The MLS (Multi-Level Security) policy is
designed as a policy where all processes are partitioned into fine-grained security
domains and confined by policy. MLS also supports the Bell And LaPadula model, where pro-
cesses are not only confined by the type but also the level of the data.
You can define which policy you will run by setting the SELINUXTYPE environment variable
within /etc/selinux/config. You must reboot and possibly relabel if you change the policy
type to have it take effect on the system. The corresponding policy configuration for
each such policy must be installed in the /etc/selinux/{SELINUXTYPE}/ directories.
A given SELinux policy can be customized further based on a set of compile-time tunable
options and a set of runtime policy booleans. system-config-selinux allows customization
of these booleans and tunables.
Many domains that are protected by SELinux also include SELinux man pages explaining how
to customize their policy.
FILE LABELING
All files, directories, devices ... have a security context/label associated with them.
These context are stored in the extended attributes of the file system. Problems with
SELinux often arise from the file system being mislabeled. This can be caused by booting
the machine with a non SELinux kernel. If you see an error message containing file_t,
that is usually a good indicator that you have a serious problem with file system label-
ing.
The best way to relabel the file system is to create the flag file /.autorelabel and
reboot. system-config-selinux, also has this capability. The restorecon/fixfiles com-
mands are also available for relabeling files.
AUTHOR
This manual page was written by Dan Walsh <dwalsh AT redhat.com>.
FILES
/etc/selinux/config
SEE ALSO
booleans(8), setsebool(8), sepolicy(8), system-config-selinux(8), togglesebool(8),
fixfiles(8), restorecon(8), setfiles(8), semanage(8), sepolicy(8), seinfo(8), sesearch(8)
Every confined service on the system has a man page in the following format:
<servicename>_selinux(8)
For example, httpd has the httpd_selinux(8) man page.
man -k selinux
Will list all SELinux man pages.
dwalsh AT redhat.com 29 Apr 2005 selinux(8)
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