man > apparmor(7)

APPARMOR(7)                                   AppArmor                                   APPARMOR(7)

NAME
       AppArmor - kernel enhancement to confine programs to a limited set of resources.

DESCRIPTION
       AppArmor is a kernel enhancement to confine programs to a limited set of resources.
       AppArmor's unique security model is to bind access control attributes to programs rather than
       to users.

       AppArmor confinement is provided via profiles loaded into the kernel via apparmor_parser(8),
       typically through the apparmor.service systemd unit, which is used like this:

               # systemctl start apparmor
               # systemctl reload apparmor

       AppArmor can operate in two modes: enforcement, and complain or learning:

       •   enforcement  -   Profiles  loaded  in  enforcement mode will result in enforcement of the
           policy defined in the profile as well as reporting policy violation attempts to syslogd.

       •   complain - Profiles loaded in  "complain" mode will not enforce policy.  Instead, it will
           report policy violation attempts. This mode is convenient  for  developing  profiles.  To
           manage   complain   mode   for  individual  profiles  the  utilities  aa-complain(8)  and
           aa-enforce(8) can be used.  These utilities take a program name as an argument.

       Profiles are traditionally stored in files  in  /etc/apparmor.d/  under  filenames  with  the
       convention  of  replacing  the  / in pathnames with . (except for the root /) so profiles are
       easier to manage (e.g. the /usr/sbin/nscd profile would be named usr.sbin.nscd).

       Profiles are applied to a process at exec(3) time  (as  seen  through  the  execve(2)  system
       call):  once  a  profile  is  loaded for a program, that program will be confined on the next
       exec(3). If a process is already running under a profile, when one replaces that  profile  in
       the kernel, the updated profile is applied immediately to that process.  On the other hand, a
       process that is already running unconfined cannot be confined.

       AppArmor  supports  the Linux kernel's securityfs filesystem, and makes available the list of
       the profiles currently loaded; to mount the filesystem:

               # mount -tsecurityfs securityfs /sys/kernel/security
               $ cat /sys/kernel/security/apparmor/profiles
               /usr/bin/mutt
               /usr/bin/gpg
                  ...

       Normally, the initscript will mount securityfs if it has not already been done.

       AppArmor also restricts what privileged operations a confined process may  execute,  even  if
       the process is running as root. A confined process cannot call the following system calls:

               create_module(2) delete_module(2) init_module(2) ioperm(2)
               iopl(2) ptrace(2) reboot(2) setdomainname(2)
               sethostname(2) swapoff(2) swapon(2) sysctl(2)

   Complain mode
       Instead  of  denying  access  to  resources the profile does not have a rule for AppArmor can
       "allow" the access and log a message for the operation  that  triggers  it.  This  is  called
       complain  mode.  It is important to note that rules that are present in the profile are still
       applied, so allow rules will still quiet or force audit messages, and deny rules  will  still
       result  in  denials and quieting of denial messages (see Turn off deny audit quieting if this
       is a problem).

       Complain mode can be used to develop profiles incrementally as an application  is  exercised.
       The  logged  accesses  can  be  added  to  the  profile  and then can the application further
       excercised to discover further  additions  that  are  needed.  Because  AppArmor  allows  the
       accesses the application will behave as it would if AppArmor was not confining it.

       Warning  complain  mode does not provide any security, only auditing, while it is enabled. It
       should not be used in a hostile environment or bad behaviors may be logged and added  to  the
       profile as if they are resource accesses that should be used by the application.

       Note  complain mode can be very noisy with new or empty profiles, but with developed profiles
       might not log anything if the profile covers the application behavior well.  See  Audit  Rate
       Limiting if complain mode is generating too many log messages.

       To  set a profile and any children or hat profiles the profile may contain into complain mode
       use

               aa-complain /etc/apparmor.d/<the-application>

       To manually set a specific profile in complain  mode,  add  the  "complain"  flag,  and  then
       manually reload the profile:

               profile foo flags=(complain) { ... }

       Note that the "complain" flag must also be added manually to any hats or children profiles of
       the profile or they will continue to use the previous mode.

       To enable complain mode globally, run:

               echo -n complain > /sys/module/apparmor/parameters/mode

       or to set it on boot add:

               apparmor.mode=complain

       as a kernel boot paramenter.

       Warning Setting complain mode gloabally disables all apparmor security protections. It can be
       useful  during  debugging or profile development, but setting it selectively on a per profile
       basis is safer.

ERRORS
       When a confined process tries to access a file it does not have  permission  to  access,  the
       kernel will report a message through audit, similar to:

               audit(1386511672.612:238): apparmor="DENIED" operation="exec"
                 parent=7589 profile="/tmp/sh" name="/bin/uname" pid=7605
                 comm="sh" requested_mask="x" denied_mask="x" fsuid=0 ouid=0

               audit(1386511672.613:239): apparmor="DENIED" operation="open"
                 parent=7589 profile="/tmp/sh" name="/bin/uname" pid=7605
                 comm="sh" requested_mask="r" denied_mask="r" fsuid=0 ouid=0

               audit(1386511772.804:246): apparmor="DENIED" operation="capable"
                 parent=7246 profile="/tmp/sh" pid=7589 comm="sh" pid=7589
                 comm="sh" capability=2  capname="dac_override"

       The  permissions  requested  by  the process are described in the operation= and denied_mask=
       (for files - capabilities etc. use a slightly different log format).  The "name" and  process
       id  of the running program are reported, as well as the profile name including any "hat" that
       may be active, separated by "//". ("Name" is in quotes, because the process name  is  limited
       to 15 bytes; it is the same as reported through the Berkeley process accounting.)

       For  confined  processes  running  under  a  profile  that  has been loaded in complain mode,
       enforcement will not take place and the log messages reported to audit will be of the form:

               audit(1386512577.017:275): apparmor="ALLOWED" operation="open"
                 parent=8012 profile="/usr/bin/du" name="/etc/apparmor.d/tunables/"
                 pid=8049 comm="du" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0

               audit(1386512577.017:276): apparmor="ALLOWED" operation="open"
                 parent=8012 profile="/usr/bin/du" name="/etc/apparmor.d/tunables/"
                 pid=8049 comm="du" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0

       If the userland auditd is not running, the kernel will send audit events to klogd; klogd will
       send the messages to syslog, which will log  the  messages  with  the  KERN  facility.  Thus,
       REJECTING   and   PERMITTING   messages   may   go   to  either  /var/log/audit/audit.log  or
       /var/log/messages, depending upon local configuration.

DEBUGGING
       AppArmor provides a few  facilities  to  log  more  information,  which  can  help  debugging
       profiles.

   Enable debug mode
       When  debug  mode  is  enabled,  AppArmor will log a few extra messages to dmesg (not via the
       audit subsystem). For example, the logs will tell  whether  environment  scrubbing  has  been
       applied.

       To enable debug mode, run:

               echo 1 > /sys/module/apparmor/parameters/debug

       or to set it on boot add:

               apparmor.debug=1

       as a kernel boot paramenter.

   Turn off deny audit quieting
       By  default,  operations that trigger "deny" rules are not logged.  This is called deny audit
       quieting.

       To turn off deny audit quieting, run:

               echo -n noquiet >/sys/module/apparmor/parameters/audit

       or to set it on boot add:

               apparmor.audit=noquiet

       as a kernel boot paramenter.

   Force audit mode
       AppArmor can log a message for every operation that triggers a rule configured in the policy.
       This is called force audit mode.

       Warning! Force audit mode can be extremely noisy even for a single profile,  let  alone  when
       enabled globally.

       To set a specific profile in force audit mode, add the "audit" flag:

               profile foo flags=(audit) { ... }

       To enable force audit mode globally, run:

               echo -n all > /sys/module/apparmor/parameters/audit

       or to set it on boot add:

               apparmor.audit=all

       as a kernel boot paramenter.

       Audit Rate Limiting

       If auditd is not running, to avoid losing too many of the extra log messages, you will likely
       have to turn off rate limiting by doing:

               echo 0 > /proc/sys/kernel/printk_ratelimit

       But even then the kernel ring buffer may overflow and you might lose messages.

       Else, if auditd is running, see auditd(8) and auditd.conf(5).

FILES
       /etc/apparmor.d/
       /var/cache/apparmor/
       /var/log/audit/audit.log
       /var/log/messages

SEE ALSO
       apparmor_parser(8),  aa_change_hat(2),  apparmor.d(5),  aa-autodep(1),  clean(1),  auditd(8),
       aa-unconfined(8), aa-enforce(1), aa-complain(1), and <https://wiki.apparmor.net>.

AppArmor 4.0.1                               2026-04-13                                  APPARMOR(7)