authorization

tools

getent

[!NOTE|label:references:]
difference between getent passwd <USER> and getent passwd | grep <USER>

getent passwd <USER> -> checking data in /var/lib/sss/mc/passwd
getent passwd | grep <USER> -> checking data in /var/lib/sss/pipes/nss

sss

[!NOTE|label:references]
Chapter 7. SSSD client-side view

# sss_override
$ sudo dnf install -y sssd-tools

sssd

sss_override management

$ sudo dnf install -y sssd-tools

check user

$ sudo sssctl user-checks <username>
user: marslo
action: acct
service: system-auth

SSSD nss user lookup result:
 - user name: marslo
 - user id: 33637
 - group id: 40048
 - gecos: Marslo Jiao (Marslo Jiao)
 - home directory: /home/marslo
 - shell: /bin/bash

InfoPipe operation failed. Check that SSSD is running and the InfoPipe responder is enabled. Make sure 'ifp' is listed in the 'services' option in sssd.conf.InfoPipe User lookup with [marslo] failed.
testing pam_acct_mgmt

pam_acct_mgmt: Success

PAM Environment:
 - no env -

# or
$ getent passwd -s sss marslo

add user name

$ sudo /usr/sbin/sss_override user-add <username> -n secondary-username

# verification
$ id secondary-username
# display the override
$ sudo /usr/sbin/sss_override user-show user-name

override the uid

# check current uid
$ id -u <username>

# overwride
$ sudo /usr/sbin/sss_override user-add <username> -u <new-uid>
$ sudo /usr/sbin/sss_cache --users
# or
$ sudo /usr/sbin/sss_cache --user <username>
$ sudo systemctl restart sssd

override the gid

# check current gid
$ id -g <username>
# or
$ id -nG <username>
# or
$ sudo lid -g <group_name>

# override
$ sudo /usr/sbin/sss_override user-add <username> -g <new-gid>
$ sudo /usr/sbin/sss_cache --users
$ sudo /usr/sbin/sss_cache --user <username>
$ sudo systemctl restart sssd

override the home directory

# check current home directory
$ getent passwd <username>

# override
$ sudo /usr/sbin/sss_override user-add <username> -h /new/home/directory
$ sudo systemctl restart sssd

override the shell attribute

# check current
$ getent passwd <username>

# override
$ sudo /usr/sbin/sss_override user-add <username> -s /new/shell
$ sudo systemctl restart sssd

# or
$ sudo /usr/sbin/sss_override user-add <username> \
       -h </original/home/directory> \
       -s /bin/bash
$ sudo systemctl restart sssd

managing the sssd cache

# clear the cache and update all records
$ sudo /usr/sbin/sss_cache [-E|--everything]

# clear invalidates cache entries for all user records
$ sudo /usr/sbin/sss_cache [-U|--users]

# clear all cached entries for a particular domain
$ sudo /usr/sbin/sss_cache [-E|--everything] [-d|--domain] <ldap_name>

# purge the records for that specific account and leave the rest of the cache intact
$ sudo /usr/sbin/sss_cache [-u|--user] <username>

# invalidates the cache entry for the specified group
$ sudo /usr/sbin/sss_cache [-g|--group] <groupname>

remove account

references:
How do you cleanup after deleting an LDAP user on RHEL 7?

$ sudo sss_override user-del [--debug 1..9] <username>
$ sudo /usr/sbin/sss_cache --everything
$ sudo systemctl restart sssd

# get info
$ loginctl

# logout
$ loginctl kill-user <username>
$ sudo /usr/sbin/sss_cache -u <username>
$ loginctl terminate-user <username>
$ sudo pkill -u <username>
$ systemctl restart sssd
$ systemctl restart accounts-daemon

tricky

sssd account cannot be deleted

$ sudo /usr/sbin/sss_cache -u devops
$ sudo /usr/sbin/sss_cache -E
$ sudo systemctl restart sssd

# verify
$ getent passwd devops
devops:*:41032:10:Service Account-Block-chain:/user/devops:/bin/tcsh
$ id devops
uid=41032(devops) gid=10(uucp) groups=10(uucp),0(root),4(adm),1000(marvell),994(docker)
$ sudo useradd -m -d '/home/devops' -u 1000 -s /bin/bash devops
useradd: user 'devops' already exists

$ hexdump -C /var/lib/sss/mc/passwd
00000000  01 00 00 f0 01 00 00 00  01 00 00 00 01 00 00 00  |................|
00000010  b1 e9 04 d3 80 ff 7f 00  66 66 00 00 c0 cc 0c 00  |........ff......|
00000020  38 00 00 00 b8 ff 7f 00  20 66 80 00 00 00 00 00  |8....... f......|
00000030  01 00 00 f0 00 00 00 00  00 00 00 f0 74 00 00 00  |............t...|
00000040  a7 14 ac 66 00 00 00 00  ff ff ff ff ff ff ff ff  |...f............|
00000050  70 db 02 00 1c 36 02 00  ff ff ff ff 00 00 00 f0  |p....6..........|
00000060  10 00 00 00 48 a0 00 00  0a 00 00 00 3c 00 00 00  |....H.......<...|
00000070  64 65 76 6f 70 73 00 2a  00 53 65 72 76 69 63 65  |devops.*.Service|
00000080  20 41 63 63 6f 75 6e 74  2d 42 6c 6f 63 6b 2d 63  | Account-Block-c|
00000090  68 61 69 6e 00 2f 75 73  65 72 2f 64 65 76 6f 70  |hain./user/devop|
000000a0  73 00 2f 62 69 6e 2f 74  63 73 68 00 ff ff ff ff  |s./bin/tcsh.....|
000000b0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
*
......

solution

[!TIP|label:references:]
login to root to execute the following commands; or use any sudo local account, otherwise the sssd account will be unavailable when sssd service is stopped !

# login to root or any sudo local account
$ sudo su -

# clean cache
$ sudo /usr/sbin/sss_cache -u devops
$ sudo /usr/sbin/sss_cache -E
$ sudo systemctl restart sssd

# stop sssd service and remove /var/lib/sss/mc/passwd
$ sudo systemctl stop sssd.service
$ sudo mv /var/lib/sss/mc/passwd{,.bak}

# create local user
$ sudo useradd -m -d '/home/devops' -u 1001 -g devops -s /bin/bash devops
$ id devops
uid=1001(devops) gid=1001(devops) groups=1001(devops)

# start sssd service
$ sudo systemctl start sssd.service

backup and restore

# export
$ /usr/sbin/sss_override user-export user-export.bak
$ /usr/sbin/sss_override group-export group-export.bak

# restore
$ /usr/sbin/sss_override user-import user-import.bak
$ /usr/sbin/sss_override group-import group-import.bak

list all override

$ /usr/sbin/sss_override user-find

sssd config

After this in /etc/sssd/sssd.conf file Specify ldap_default_bind_dn and ldap_default_authtok as default bind dn and password respectively, this depends upon your ldap setup.
references:
Chapter 13. Configuring Authentication

# optional
$ yum install -y sssd \
                 realmd \
                 oddjob \
                 oddjob-mkhomedir \
                 adcli \
                 samba-common \
                 samba-common-tools \
                 krb5-workstation \
                 openldap-clients \
                 policycoreutils-python \
                 authselect-compat \
                 ntpdate \
                 ntp
$ authselect select sssd
$ authselect select sssd with-mkhomedir
$ systemctl enable oddjobd.service
$ systemctl start oddjobd.service

$ authconfig --enablesssd \
             --enablesssdauth \
             --enablelocauthorize \
             --enableldap \
             --enableldapauth \
             --ldapserver=ldap://ipaserver.example.com:389 \
             --disableldaptls \
             --ldapbasedn=dc=example,dc=com \
             --enablerfc2307bis \
             --enablemkhomedir \
             --enablecachecreds \
             --update

other sssd config

references:
2.2. PAM Configuration Files
Chapter 4. Hardening Your System with Tools and Services
21.2.2. Mounting NFS File Systems using autofs
13.2.28. Managing the SSSD Cache

config files

file

comments

/etc/krb5.keytab

host keytab file

/etc/nsswitch.conf

Name Service Switch (NSS) configuration file

/etc/sssd/sssd.conf

sssd configure file

/etc/auto.master

mount NFS

/etc/auto.misc

automount utility can mount and unmount NFS

/etc/pam.d/password-auth

PAM module

/etc/pam.d/system-auth

PAM module

/var/lib/sss/db/*

sssd cache

/etc/security/access.conf

local login access control table

discovery domain

$ realm discover my.com [--server-software=active-directory]
my.com
  type: kerberos
  realm-name: MY.COM
  domain-name: my.com
  configured: no
  server-software: active-directory
  client-software: sssd
  required-package: oddjob
  required-package: oddjob-mkhomedir
  required-package: sssd
  required-package: adcli
  required-package: samba-common-tools

join the system

$ realm join <my.domain> -U <account> [--membership-software=samba] [--verbose] [--install]

troubleshooting

sudo: unable to dlopen /usr/lib/libsss_sudo.so

[!NOTE|label:issue:]

sudo: unable to load /usr/lib/x86_64-linux-gnu/libsss_sudo.so: /usr/lib/x86_64-linux-gnu/libsss_sudo.so: cannot open shared object file: No such file or directory
sudo: unable to initialize SSS source. Is SSSD installed on your machine?

$ sudo apt install libsss-sudo

local

user

`subuid` & `subgid`

[!NOTE|label:references:]
Podman
check subuid and subgid from /etc/subuid and /etc/subgid

# rootless mode
$ sudo usermod --add-subuids 10000-75535 USERNAME
$ sudo usermod --add-subgids 10000-75535 USERNAME

# or
$ echo USERNAME:10000:65536 >> /etc/subuid
$ echo USERNAME:10000:65536 >> /etc/subgid

references:
how to list users and groups on linux
How to Create Groups in Linux (groupadd Command)
understanding /etc/shadow file format on linux
understanding the /etc/shadow file
linux: instructions on using commands about user and group on linux

find users
/etc/passwd
/etc/shadow
/etc/pam.d/passwd more on users
/etc/login.defs

local user management

useradd

create user devops

$ useradd -c "comments here" \
          -m \
          -d "/home/devops" \
          -u 1000 \
          -g 1000 \
          -s /bin/bash \
          devops

$ useradd --comment "comments here" \
          --create-home \
          --home-dir /home/devops \
          --shell /bin/bash \
          --uid 1000 \
          --gid 1000 \
          --user-group devops
          devops

full steps

$ uid='1000'
$ gid='1000'
$ user='devops'

$ mkdir -p /home/${user}
$ chown -R ${uid}:${gid} /home/${user}
$ groupadd -g ${gid} ${user}
$ useradd -c "create user ${user}" \
          -d "/home/${user}" \
          -u ${uid} \
          -g ${gid} \
          -m \
          -s /bin/bash \
          ${user}

deluser for ubunut

[!NOTE|label:references:]
deluser - remove a user from the system
userdel - delete a user account and group ( if possible )

deluser, delgroup - remove a user or group from the system

SYNOPSIS
deluser [options] [--force] [--remove-home] [--remove-all-files] [--backup] [--backup-to DIR] user
deluser --group [options] group
delgroup [options] [--only-if-empty] group
deluser [options] user group

$ deluser <account> <group>

new user with root uid

[!TIP]
username: test1
password: password1

$ /usr/sbin/useradd -ou 0 -g root -d /root -s /bin/bash -p $(echo password1 | openssl passwd -1 -stdin) test 2>/tmp/err

generate secure password to userwith chpasswd

$ echo "encryptedpassword" | openssl passwd -1 -stdin

# or
$ echo "test:$(echo password | openssl passwd -1 -stdin -salt abcde)" | sudo chpasswd -e

group

/etc/group
/etc/passwd
/etc/shadow

references:
Linux groupadd command

get group

list all groups

$ getent group

# or
$ getent group <GID|GNAME>

get gid

$ sudo lid -g <group_name>
# or
$ getent group <group_name>

create group

create group with random gid

$ sudo groupadd <group_name>

get available gid

for error:

groupadd: GID 'xxxx' already exists

$ gname='mytestgroup'
$ sudo groupadd ${gname}

$ getent group ${gname} | cut -d: -f3
# or
$ sed -nr "s/^${gname}:x:([0-9]+):.*/\1/p" /etc/group
# or
$ grep "^${gname}" /etc/group | cut -d: -f3

# and finally remove the group
$ sudo groupdel ${gname}

create group with particular gid

$ sudo groupadd -g <gid> <group_name>

create group with existing gid

[!TIP]

-o (--non-unique) option the groupadd command allows you to create a group with non-unique GID

troubleshooting

issue:

/usr/bin/id: cannot find name for group ID xxxx

solution
```
$ groupadd --gid <GID> <GROUP_NAME>
```

$ sudo groupadd -o -g <new_gid> <group_name>

create group with password
```
$ groupadd -p secretpassword writers
```

add system group

[!NOTE|label:-r or --system ]

$ groupadd -r hardwareteam
$ groupadd --system hardwareteam

modify group

[!NOTE|label:references:]
Change gid of a specific group

$ sudo groupmod -o -g <gid> <group_name>

# change file mode
$ find / -gid OLD_GID ! -type l -exec chgrp NEW_GID {} \;

groupmod: group 'xxx' does not exist in /etc/group

$ getent group 994
gl3:*:994:

# check available GID
$ getent group 1994

# modify GID
$ sudo groupmod -o -g 1994 gl3
groupmod: group 'gl3' does not exist in /etc/group
$ sudo echo 'gl3:*:994:' >> /etc/group
$ grep gl3 /etc/group
gl3:*:994:

$ sudo groupmod -o -g 1994 gl3
$ sudo groupmod -o -g 994 docker

# verify
$ getent group docker
docker:x:994:marslo,devops
$ getent group gl3
gl3:*:1994:

manager group users

add user into group

$ sudo usermod -a -G adm,root,docker,wheel devops
$ sudo usermod -a -G sudo devops

remove user from group

How to Add or Remove a User from a Group in Linux

$ gpasswd -d <account> <group>

# or ubuntu
$ sudo deluser <account> <group>

tips

list account permission

$ sudo -l -U marslo
User marslo may run the following commands on kuberentes-01:
    (ALL) NOPASSWD: ALL
    (ALL) NOPASSWD: /usr/bin/su - devops

check account locale

[!NOTE|label:references:]
* iMarslo: check and set locale

$ sudo su -l -c locale marslo
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=en_US.UTF-8

logout

$ pkill -KILL -u ${useranme}

$ who -uH
NAME     LINE         TIME             IDLE          PID COMMENT
devops   pts/0        2022-06-14 05:44 00:17       41455 (192.168.1.1)
marslo   pts/1        2022-06-14 05:58   .         50162 (192.168.1.1)
$ sudo kill  41455
$ who -uH
NAME     LINE         TIME             IDLE          PID COMMENT
marslo   pts/1        2022-06-14 05:58   .         50162 (192.168.1.1)

or : loginctl

# get login details
$ loginctl

# logout
$ loginctl kill-user <username>

view users password properties in linux

$ chage -l marslo
Last password change      : Mar 09, 2022
Password expires          : never
Password inactive         : never
Account expires           : never
Minimum number of days between password change    : 0
Maximum number of days between password change    : 99999
Number of days of warning before password expires : 7

hash_algorithm

Code

Algorithm

$1

MD5 hashing algorithm

$2

Blowfish Algorithm

$3

Eksblowfish Algorithm

$4

NT hashing algorithm

$5

SHA-256 Algorithm

$6

SHA-512 Algorithm

authentication in RHEL

[!NOTE|label:references:]
Configuring authentication and authorization in RHEL

$ sudo dnf install -y oddjob-mkhomedir
$ sudo systemctl enable --now oddjobd.service

$ sudo authconfig --enablemkhomedir --update
$ sudo authselect select sssd with-mkhomedir --force

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Last updated 2 months ago

Was this helpful?

tools

getent

sss

sssd

sss_override management

check user

add user name

override the uid

override the gid

override the home directory

override the shell attribute

managing the sssd cache

remove account

backup and restore

list all override

sssd config

other sssd config

troubleshooting

local

user

subuid & subgid

local user management

group

get group

create group

modify group

manager group users

tips

list account permission

check account locale

logout

view users password properties in linux

hash_algorithm

authentication in RHEL

`subuid` & `subgid`