user-keyring - Per-user keyring


   The  user keyring is a keyring used to anchor keys on behalf of a user.
   Each UID the kernel deals with has its own user keyring.  This  keyring
   is  associated  with  the  record that the kernel maintains for the UID
   and, once created, is retained as long as that record persists.  It  is
   shared amongst all processes of that UID.

   The  user  keyring  is  created  on  demand  when a thread requests it.
   Normally, this happens when pam_keyinit is invoked when a user logs in.

   The user keyring is not searched by default by request_key().  When the
   pam_keyinit  module  creates a session keyring, it adds to it a link to
   the user keyring so that the user keyring will  be  searched  when  the
   session keyring is.

   A  special  serial number value, KEY_SPEC_USER_KEYRING, is defined that
   can be used in lieu of the  calling  process's  user  keyring's  actual
   serial number.

   From  the  keyctl utility, '@u' can be used instead of a numeric key ID
   in much the same way.

   User keyrings are independent of clone(), fork(), vfork(), execve() and
   exit()  excepting  that the keyring is destroyed when the UID record is
   destroyed when the last process pinning it exits.

   If it necessary to for a key associated with a user to exist beyond the
   UID  record  being  garbage  collected  - for example for use by a cron
   script - then the persistent keyring should be used instead.

   If a user keyring does not exist  when  it  is  accessed,  it  will  be




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