разрешение имен пользователей и групп UNIX для поиска пользователей / групп через Varlink (UNIX user and group name resolution for user/group lookup via Varlink)
Имя (Name)
nss-systemd, libnss_systemd.so.2 - UNIX user and group name
resolution for user/group lookup via Varlink
Синопсис (Synopsis)
libnss_systemd.so.2
Описание (Description)
nss-systemd is a plug-in module for the GNU Name Service Switch
(NSS) functionality of the GNU C Library (glibc), providing UNIX
user and group name resolution for services implementing the
User/Group Record Lookup API via Varlink
This module also ensures that the root and nobody users and
groups (i.e. the users/groups with the UIDs/GIDs 0 and 65534)
remain resolvable at all times, even if they aren't listed in
/etc/passwd or /etc/group, or if these files are missing.
This module preferably utilizes systemd-userdbd.service(8) for
resolving users and groups, but also works without the service
running.
To activate the NSS module, add "systemd" to the lines starting
with "passwd:", "group:", "shadow:" and "gshadow:" in
/etc/nsswitch.conf.
It is recommended to place "systemd" after the "files" or
"compat" entry of the /etc/nsswitch.conf lines so that
/etc/passwd, /etc/group, /etc/shadow and /etc/gshadow based
mappings take precedence.
STATIC DROP-IN JSON USER/GROUP RECORDS
Besides user/group records acquired via the aforementioned
Varlink IPC interfaces and the synthesized root and nobody
accounts, this module also makes user and group accounts
available to the system that are defined in static drop-in files
in the /etc/userdb/, /run/userdb/, /run/host/userdb/ and
/usr/lib/userdb/ directories.
This is a simple mechanism to provide static user and group
records via JSON drop-in files. Such user records should be
defined in the format described by the JSON User Records
-rw-r--r--. 1 root root 723 May 10 foobar.user
-rw-------. 1 root root 123 May 10 foobar.user-privileged
lrwxrwxrwx. 1 root root 19 May 10 4711.user -> foobar.user
lrwxrwxrwx. 1 root root 19 May 10 4711.user-privileged -> foobar.user-privileged
Similarly, group records following the format described in JSON
Group Record
The primary user/group record files (i.e. those with the .user
and .group suffixes) should not contain the "privileged" section
as described in the specifications. The privileged user/group
record files (i.e. those with the .user-privileged and
.group-privileged suffixes) should contain this section,
exclusively.
Note that static user/group records generally do not override
conflicting records in /etc/passwd or /etc/group or other account
databases. In fact, before dropping in these files a reasonable
level of care should be taken to avoid user/group name and
UID/GID conflicts.
Конфигурация в /etc/nsswitch.conf (Configuration in /etc/nsswitch.conf)
Here is an example /etc/nsswitch.conf file that enables
nss-systemd correctly:
passwd: compat systemd
group: compat [SUCCESS=merge] systemd
shadow: compat systemd
gshadow: files systemd
hosts: mymachines resolve [!UNAVAIL=return] files myhostname dns
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis
EXAMPLE: MAPPINGS PROVIDED BY SYSTEMD-MACHINED.SERVICE
The container "rawhide" is spawned using systemd-nspawn(1):
# systemd-nspawn -M rawhide --boot --network-veth --private-users=pick
Spawning container rawhide on /var/lib/machines/rawhide.
Selected user namespace base 20119552 and range 65536.
...
$ machinectl --max-addresses=3
MACHINE CLASS SERVICE OS VERSION ADDRESSES
rawhide container systemd-nspawn fedora 30 169.254.40.164 fe80::94aa:3aff:fe7b:d4b9
$ getent passwd vu-rawhide-0 vu-rawhide-81
vu-rawhide-0:*:20119552:65534:vu-rawhide-0:/:/usr/sbin/nologin
vu-rawhide-81:*:20119633:65534:vu-rawhide-81:/:/usr/sbin/nologin
$ getent group vg-rawhide-0 vg-rawhide-81
vg-rawhide-0:*:20119552:
vg-rawhide-81:*:20119633:
$ ps -o user:15,pid,tty,command -e|grep '^vu-rawhide'
vu-rawhide-0 692 ? /usr/lib/systemd/systemd
vu-rawhide-0 731 ? /usr/lib/systemd/systemd-journald
vu-rawhide-192 734 ? /usr/lib/systemd/systemd-networkd
vu-rawhide-193 738 ? /usr/lib/systemd/systemd-resolved
vu-rawhide-0 742 ? /usr/lib/systemd/systemd-logind
vu-rawhide-81 744 ? /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
vu-rawhide-0 746 ? /usr/sbin/sshd -D ...
vu-rawhide-0 752 ? /usr/lib/systemd/systemd --user
vu-rawhide-0 753 ? (sd-pam)
vu-rawhide-0 1628 ? login -- zbyszek
vu-rawhide-1000 1630 ? /usr/lib/systemd/systemd --user
vu-rawhide-1000 1631 ? (sd-pam)
vu-rawhide-1000 1637 pts/8 -zsh
Смотри также (See also)
systemd(1), systemd.exec(5), nss-resolve(8), nss-myhostname(8),
nss-mymachines(8), systemd-userdbd.service(8),
systemd-homed.service(8), systemd-machined.service(8),
nsswitch.conf(5), getent(1)
Примечание (Note)
1. User/Group Record Lookup API via Varlink
https://systemd.io/USER_GROUP_API
2. JSON User Records
https://systemd.io/USER_RECORD
3. JSON Group Record
https://systemd.io/GROUP_RECORD
