2 Administering Users & 3 Configure Perms

Question 1

User passwd fields

Answer 1

username
passwd
uid
gid
comment
home dir
login shell

Question 2

User shadow fields

Answer 2

-username
-passwd
-days since change
-day before may change
-days before must change
-days until max warned to change
-days to account disable after expire
-days until expire
-reserved

Question 3

/etc/profile

Answer 3

set system wide enviroment variables (e.g. mail notification) and start up programs

Question 4

/etc/bashrc

Answer 4

system wide functions and aliases for new user shells

Question 5

~/.bash_profile

Answer 5

Login shell that can source the .profile file and runs upon user login in the background . Set user-specific variables for new shell login sessions

Question 6

~/.bashrc

Answer 6

Interactive shell that runs the terminal and accepts user inputs for specific outputs. Can apply user-specific variables and configs/preferences for each login session like aliases

Question 7

/etc/skel

Answer 7

files copied to home directory of new user, prepopulates config files life .bashrc with suggested settings or policy docs

Question 8

/etc/login.def

Answer 8

define default account settings:
-mail box location,
- passwd aging values,
-uid,
-guid,
-home dir creation,
-umask,
-pass encryp hash & methods (AES)
display: useradd -D

Question 9

useradd -c -e -m -s -u -D

Answer 9

-c comment
-e expiration yyyy-mm-dd
-m home dir
-s shell
-u uid
-D default settings

Question 10

usermod/del error codes 0,1,2,6,8

Answer 10

0 success
1 couldn’t update passwd file
2 invalid syntax
6 specified user doesn’t exist
8 cannot del, user logged in

Question 11

who , w

Answer 11

who : displays login sessions
w : displays specific users logged in and idle time

Question 12

id {uname}

Answer 12

display uid, guid, group memberships

Question 13

passwd -d -e -l -u

Answer 13

-d del
-e expire passwd for change
-l lock account
-u unlock account

Question 14

chage -l

Answer 14

display:
-last passwd change date
-Password expiration date
-Account inactive date
-account expiration date
-min days between pass changes
-max days between pass changes
- # days before pass expiration before warning

Question 15

chage -l -M -m -W -E

Answer 15

-l display values
-M max # of days between pass changes
-m min # of days between pass changes
-W days before pass expiration before warning
-E lock account after date

Question 16

pam_faillock

Answer 16

tracks login attempts and can configure policies after # failed attempts for lockout

display tally of logins attempts with faillock

Question 17

/etc/group

Answer 17

groups and memberships

Question 18

group commands

Answer 18

groupadd,
groupmod,
groupdel,
gpasswd

Question 19

groupadd error code 0,2,4,9

Answer 19

0 succes
2 invalid syntax argument
4 GID not unique
9 Group name not unique

Question 20

groupmod/del 0,2,6,8,10

Answer 20

0 success
2 invalid command syntax
6 group don’t exists
8 cant remove user primary group (del)
10 cant update group

Question 21

how are users given root privileges

Answer 21

sudo, which is delegated from the /etc/sudoers file but edit must be done from visudo to ensure correctness

-sudo -l displays sudo privileges

Question 22

visudo -c -f -s -x

Answer 22

-s check file for errors
-f edit file in different location
-s check file in strict mode: aliases used before defined will cause error
-x output file in to a file in JSON format

Question 23

how to edit visudoers file to add priviliegs

Answer 23

-full privileges are done with “ uname ALL=(ALL:ALL) ALL “

-specific privileges without passwd “uname ALL=(ALL) NOPASSWD: SHUTDOWN_CMDS”
: assuming
shutdown_cmds is
an alias for all
related
shutdown
commands

-allow use of sudo edit “%editors ALL - sudoedit /path/to/file”

Question 24

wheel group

Answer 24

gives users root privileges with use of sudo

visudo can edit this groups privileges

Question 25

sudoedit /path/to/file

Answer 25

allows edit of files requiring root privileges using their own privileges

Question 26

polkit

Answer 26

delegates specific root actions than sudo allowing aliases of cmd groups

rules for actions written in XML files /usr/share/polkit-1/actions “*.policy”

Question 27

polkit cmds: pkexec

Answer 27

allow user to execute an action

” sudo pkexec useradd uname “

Question 28

polkit cmd: pkaction

Answer 28

diplays details about an action

Question 29

polkit cmd: pkcheck

Answer 29

displays whether a process is authorized

Question 30

polkit cmd: pkttyagent

Answer 30

provide text-based authentication

Question 31

halt processes for users

Answer 31

sudo killall -u uname

Question 32

login processes from boot

Answer 32

1. The operating system boots and the kernel is loaded. Assume the system boots to the CLI and displays an authentication prompt.
2. The user enters a name and password combination. These are checked against the /etc/passwd and /etc/shadow files. Settings such as expired passwords and locked accounts are checked for at this point.
3. System and user profile files are processed, and the user is presented with an authenticated and customized environment.

Question 33

lastlog command

Answer 33

tracks latest login attempts recorded in /var/log/lastlog

Question 34

last command

Answer 34

displays wtmp file including every login and logoff and can filter time stamps

found in /var/log/wtmp

Question 35

chown and chmod

Answer 35

chown : alters ownership and group
chown {user}:{group} or chown :{group}

chgrp : group ownership

chmod : alters permissions of dir/file with rwx

-R recursive

Question 36

rwx

Answer 36

r - read files and list dir
w - save write changes to files : w/ (x) perm - create, rename, execute files in dir
x - run scripts, program, software file, access dir and execute file from dir, or perform task on dir

Question 37

lsattr -R -a -d -v chattr -R -v +i -i

Answer 37

lsattr:
-R recursively list attr in dir and contents
-a ls all files
-d ls dir not files
-v ls version # file
chattr:
-R recursively change attr
-v {version} set version number of file
- “+i” mark as immutable
- “-i” remove immutable

chattr [-R] [-v {version}] [+-{attributes}] {file/directory names}

even root affected by immutable flag

Question 38

setUID or setGID

Answer 38

set users to have similar permissions as file or group owner.
New files set with setGID will inherit the SGID and the dir ID instead of GID of user.
this doesn’t affect existing files even moved

Question 39

how to set SUID or SGID

Answer 39

SUID chmod u+s {file}
GUID chmod g+s {file}

SUID chmod 4— {file}
SUID chmod 2— {file}

removing uses “-“ in symbolic and “0” on the 4/2 in absolute

Question 40

sticky bit and how to set

Answer 40

similar to immutable but protects files in dir from users with wx privileges. root and owner can still delete file/dir

set: +/1 add -/0 remove
chmod {+ or -} t {dir}
chmod {1 or 0}— {dir}

viewed with a t or T (if x perm not set) int the other users x bit

Question 41

ACL

Answer 41

assigns specific perms to individual users instead of only being able to set perm by a user, a group, and all others

also allows multiple users or groups presume ownership of files/dir with rwx perms of a file

doesn’t replace perms

Question 42

getfacl

Answer 42

display exiting ACL settings for a file

Question 43

setfacl -R -s -m -x -b

Answer 43

change ACL file perms:
-R recursively set
ACL options
-s set ACL replacing exiting ACL
-m Modify existing ACL
-x Remove ACL entries
-b Remove all ACL entries

setfacl [-bR] [-mx {u or g}:{u or g name}:{perm}] {file/directory names}

”,” can separate multiple acl_spec entries for u or g entries but don’t use a space