USER-KEYRING
Section: Linux Programmer's Manual (7)
Updated: 2017-03-13
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NAME
user-keyring - per-user keyring
DESCRIPTION
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 that
is shared by all processes with that UID.
The user keyring has a name (description) of the form
_uid.<UID>
where
<UID>
is the user ID of the corresponding user.
The user keyring is associated with the record that the kernel maintains
for the UID.
It comes into existence upon the first attempt to access either the
user keyring, the
user-session-keyring(7),
or the
session-keyring(7).
The keyring remains pinned in existence so long as there are processes
running with that real UID or files opened by those processes remain open.
(The keyring can also be pinned indefinitely by linking it
into another keyring.)
Typically, the user keyring is created by
pam_keyinit(8)
when a user logs in.
The user keyring is not searched by default by
request_key(2).
When
pam_keyinit(8)
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 actual serial number of
the calling process's user keyring.
From the
keyctl(1)
utility, '@u' can be used instead of a numeric key ID in
much the same way.
User keyrings are independent of
clone(2),
fork(2),
vfork(2),
execve(2),
and
_exit(2)
excepting that the keyring is destroyed when the UID record is destroyed when
the last process pinning it exits.
If it is necessary for a key associated with a user to exist beyond the UID
record being garbage collected---for example, for use by a
cron(8)
script---then the
persistent-keyring(7)
should be used instead.
If a user keyring does not exist when it is accessed, it will be created.
SEE ALSO
keyctl(1),
keyctl(3),
keyrings(7),
persistent-keyring(7),
process-keyring(7),
session-keyring(7),
thread-keyring(7),
user-session-keyring(7),
pam_keyinit(8)
COLOPHON
This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
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- DESCRIPTION
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- SEE ALSO
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- COLOPHON
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