Documentation/sysctl/user.txt

   1 Documentation for /proc/sys/user/*      kernel version 4.9.0
   2         (c) 2016                Eric Biederman <ebiederm@xmission.com>
   3
   4 ==============================================================
   5
   6 This file contains the documetation for the sysctl files in
   7 /proc/sys/user.
   8
   9 The files in this directory can be used to override the default
  10 limits on the number of namespaces and other objects that have
  11 per user per user namespace limits.
  12
  13 The primary purpose of these limits is to stop programs that
  14 malfunction and attempt to create a ridiculous number of objects,
  15 before the malfunction becomes a system wide problem.  It is the
  16 intention that the defaults of these limits are set high enough that
  17 no program in normal operation should run into these limits.
  18
  19 The creation of per user per user namespace objects are charged to
  20 the user in the user namespace who created the object and
  21 verified to be below the per user limit in that user namespace.
  22
  23 The creation of objects is also charged to all of the users
  24 who created user namespaces the creation of the object happens
  25 in (user namespaces can be nested) and verified to be below the per user
  26 limits in the user namespaces of those users.
  27
  28 This recursive counting of created objects ensures that creating a
  29 user namespace does not allow a user to escape their current limits.
  30
  31 Currently, these files are in /proc/sys/user:
  32
  33 - max_cgroup_namespaces
  34
  35   The maximum number of cgroup namespaces that any user in the current
  36   user namespace may create.
  37
  38 - max_ipc_namespaces
  39
  40   The maximum number of ipc namespaces that any user in the current
  41   user namespace may create.
  42
  43 - max_mnt_namespaces
  44
  45   The maximum number of mount namespaces that any user in the current
  46   user namespace may create.
  47
  48 - max_net_namespaces
  49
  50   The maximum number of network namespaces that any user in the
  51   current user namespace may create.
  52
  53 - max_pid_namespaces
  54
  55   The maximum number of pid namespaces that any user in the current
  56   user namespace may create.
  57
  58 - max_user_namespaces
  59
  60   The maximum number of user namespaces that any user in the current
  61   user namespace may create.
  62
  63 - max_uts_namespaces
  64
  65   The maximum number of user namespaces that any user in the current
  66   user namespace may create.