Initial Settings : Sudo Settings2022/04/25

	Configure Sudo to separate users' duty if some people share privileges.
[1]	Install Sudo.

root@localhost:~#

apt -y install sudo

[2]	Grant root privilege to a user all.

root@localhost:~#

visudo

# add to the end: user [ubuntu] can use all root privilege

ubuntu    ALL=(ALL:ALL) ALL

# how to write ⇒ [user] [host=(owner)] [command]
# push [Ctrl + x] key to quit visudo

# verify with user [ubuntu]

ubuntu@dlp:~$

/sbin/reboot

Failed to set wall message, ignoring: Interactive authentication required.
Failed to reboot system via logind: Interactive authentication required.
Failed to open initctl fifo: Permission denied
Failed to talk to init daemon.

# denied normally

ubuntu@dlp:~$

sudo /sbin/reboot

[sudo] password for ubuntu:                # password of [ubuntu]

Session terminated, terminating shell...   # run normally

[3]	In addition to the setting of [1], add settings that some commands are not allowed.

root@localhost:~#

visudo

# add alias for the kind of shutdown commands

# Cmnd alias specification

Cmnd_Alias SHUTDOWN = /sbin/halt, /sbin/shutdown, \
/sbin/poweroff, /sbin/reboot, /sbin/init, /bin/systemctl

# add (commands in alias [SHUTDOWN] are not allowed)

ubuntu    ALL=(ALL:ALL) ALL, !SHUTDOWN

# verify with user [ubuntu]

ubuntu@dlp:~$

sudo /sbin/shutdown -r now

[sudo] password for ubuntu:

Sorry, user ubuntu is not allowed to execute '/sbin/shutdown -r now' as root on ubuntu.
# denied normally

[4]	Grant privilege of some commands to users in a group.

root@localhost:~#

visudo

# add alias for the kind of user management comamnds

# Cmnd alias specification
Cmnd_Alias USERMGR = /usr/sbin/adduser, /usr/sbin/useradd, /usr/sbin/newusers, \
/usr/sbin/deluser, /usr/sbin/userdel, /usr/sbin/usermod, /usr/bin/passwd

# add to the end

%usermgr ALL=(ALL) USERMGR

root@localhost:~#

groupadd usermgr

root@localhost:~#

vi /etc/group

# add a user in this group

usermgr:x:1002:

ubuntu

# verify with user [ubuntu]

ubuntu@dlp:~$

sudo /usr/sbin/useradd testuser

ubuntu@dlp:~$

# run normally

ubuntu@dlp:~$

sudo /usr/bin/passwd testuser

Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

[5]	Grant privilege of some commands to a user.

root@localhost:~#

visudo

# add to the end for each user setting

fedora    ALL=(ALL:ALL) /usr/sbin/visudo
centos    ALL=(ALL:ALL) /usr/sbin/adduser, /usr/sbin/useradd, /usr/sbin/newusers, \
                        /usr/sbin/deluser, /usr/sbin/userdel, /usr/sbin/usermod, /usr/bin/passwd
debian    ALL=(ALL:ALL) /usr/bin/vim

# verify with user [fedora]

fedora@dlp:~$

sudo /usr/sbin/visudo

# run normally

## Sudoers allows particular users to run various commands as
## the root user, without needing the root password.

# verify with user [centos]

centos@dlp:~$

sudo /usr/sbin/userdel -r testuser

centos@dlp:~$

# run normally

# verify with user [debian]

debian@dlp:~$

sudo /usr/bin/vim /root/.profile

# run normally

# ~/.profile: executed by Bourne-compatible login shells.

[6]	It's possible to display Sudo logs on Journald ( with [journalctl] command ) or Rsyslogd ( in [/var/log/auth.log] file ), however, if you'd like to keep only Sudo logs in another file, Configure like follows.

root@localhost:~#

visudo

# add to the end

Defaults syslog=local1

root@localhost:~#

vi /etc/rsyslog.d/50-default.conf

# line 8 : add

local1.*                        /var/log/sudo.log

auth,authpriv.*;local1.none     /var/log/auth.log
*.*;auth,authpriv.none          -/var/log/syslog

root@localhost:~#

systemctl restart rsyslog

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