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®, 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 disabled, 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 application 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 application 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  system.   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 processes 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 labeling.

       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 restorcon/fixfiles commands are also available for
       relabeling files.

AUTHOR

       This manual page was written by Dan Walsh <dwalsh@redhat.com>.

FILES

       /etc/selinux/config

SEE ALSO

       booleans(8), setsebool(8), sepolicy(8), system-config-selinux(8), togglesebool(8), restorecon(8),
       fixfiles(8), setfiles(8), semanage(8), sepolicy(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.