Linux - EVERYTHING Flashcards
(243 cards)
1
Q
Term/Command
A
Description
2
Q
/home
A
Directory containing user home directories
3
Q
/root
A
Home directory for the root user
4
Q
/etc/passwd
A
File containing user account information
5
Q
/etc/shadow
A
File containing encrypted passwords and other security information for user accounts
6
Q
/etc/group
A
File containing group account information
7
Q
/etc/gshadow
A
File containing encrypted passwords and other security information for group accounts
8
Q
/etc/dnf.conf
A
Configuration file for the DNF package manager
9
Q
/etc/ssh/sshd_config
A
Configuration file for the SSH daemon
10
Q
/etc/yum.repos.d/
A
Directory containing YUM repository configuration files
11
Q
/etc/hostname
A
File containing the system hostname
12
Q
/etc/hosts
A
File mapping hostnames to IP addresses
13
Q
/etc/resolv.conf
A
File containing DNS resolver configuration
14
Q
alias
A
Command to create aliases for other commands
15
Q
bash
A
Command to execute the Bash shell
16
Q
cat
A
Command to concatenate and display file contents
17
Q
cut
A
Command to extract sections from each line of files
18
Q
dnf
A
Package manager command for Fedora/RHEL
19
Q
echo
A
Command to display a line of text
20
Q
env
A
Command to display environment variables
21
Q
export
A
Command to export environment variables from parent to child processes
22
Q
file
A
Command to determine file type. file filename
23
Q
grep
A
Command to search text patterns in files
24
Q
gzip
A
Command to compress files
25
gunzip
Command to decompress gzip files
26
head
Command to display the beginning of files
27
history
Command to display command history
28
less
Command to view files with pagination
29
let
Command for (variable) integer arithmetic in Bash. For example: let y="234+58". Echo $y. 292
30
locate
Command to find files by name
31
man
Command to display manual pages
32
nologin
Shell used for users who are not allowed to log in. Not really a shell but more like a placeholder for disabled users.
33
pwd
Command to print current working directory
34
set
Command to set or unset shell options and positional parameters
35
sort
Command to sort lines of text files
36
tail
Command to display the end of files
37
tar
Compress a group of files into an achive
38
tee
Command to read from standard input and write to standard output and files simultaneously
39
tr
Command to translate or delete characters
40
type
Command to display information about commands
41
umask
Command to set default permissions for new files and directories
42
uniq
Command to remove duplicate lines from sorted files
43
unset
Command to unset environment variables
44
wc
Command to count words, lines, and characters in a file
45
whereis
Command to locate binary, source, and manual page files for a command
46
which
Command to display the full path of shell commands
47
whoami
Command to display the current username
48
cp
Command to copy files and directories
49
find
Command to search for files in a directory hierarchy
50
ln
Command to create links between files
51
ls
Command to list directory contents
52
mkdir
Command to create directories
53
mv
Command to move or rename files and directories
54
rm
Command to remove files or directories
55
rmdir
Command to remove empty directories
56
touch
Command to create empty files or update file timestamps
57
bg
Command to move a job to the background
58
chage
Command to change user password expiry information
59
chfn
Command to change user information
60
chgrp
Command to change group ownership of files and directories
61
chmod
Command to change file permissions
62
chown
Command to change file owner and group
63
chsh
Command to change the user's login shell
64
fg
Command to bring a job to the foreground
65
free
Command to display amount of free and used memory in the system
66
groupadd
Command to create a new group
67
groupdel
Command to delete a group
68
groupmod
Command to modify a group
69
iostat
Command to display CPU and I/O statistics
70
jobs
Command to list active jobs
71
kill
Command to send signals to processes
72
killall
Command to kill processes by name
73
nice
Command to run a command with modified scheduling priority
74
passwd
Command to change user password
75
pkill
Command to send signals to processes based on name
76
ps
Command to display information about processes
77
pstree
Command to display a tree of processes
78
renice
Command to alter the priority of running processes
79
rpm
Package manager command for RPM-based Linux distributions
80
shutdown
Command to shut down or reboot the system
81
su
Command to switch user
82
sudo
Command to execute a command as another user with superuser privileges
83
top
Command to display system resource usage and running processes
84
updatedb
Command to update the file database used by locate
85
useradd
Command to create a new user
86
userdel
Command to delete a user
87
usermod
Command to modify user account attributes
88
watch
Command to execute a program periodically and display the output
89
uname
Command to display system information
90
dig
Command-line DNS lookup utility
91
host
Command-line utility for performing DNS lookups
92
hostname
Command to display or set the system's hostname
93
ip
Command to show/manipulate routing, devices, policy routing, and tunnels
94
ping
Command to send ICMP Echo Request to network hosts
95
ping6
Command to send ICMPv6 Echo Request to network hosts
96
ss
Command to investigate sockets
97
tracepath
Command to discover the MTU along the path to a target destination
98
traceroute
Command to trace the route that packets take to reach a network host
99
traceroute6
Command to trace the route that IPv6 packets take to reach a network host
100
nmcli
Command-line interface for NetworkManager
101
ssh
Command to connect to a remote machine securely using the SSH protocol
102
ssh-copy-id
Command to copy SSH keys to a remote server's authorized keys file
103
ssh-keygen
Command to generate, manage, and convert authentication keys for SSH
104
OpenSSH
Suite of secure networking utilities based on the SSH protocol
105
NetworkManager
Daemon managing network connections and devices
106
sshd
SSH daemon responsible for securely accepting connections, providing shell access, etc.
107
systemctl
Command to control systemd system and service manager
108
systemctl --version
Command to display the systemd version
109
systemctl is-active
Command to check if a unit is active
110
systemctl isolate multi-user.target
Command to change the system state to multi-user mode
111
systemctl isolate graphical.target
Command to change the system state to graphical mode
112
systemctl status x.service
Command to display status of a specific service
113
systemctl stop x.service
Command to stop a specific service
114
systemctl enable x.service
Command to enable a specific service to start automatically at boot
115
systemctl disable x.service
Command to disable a specific service from starting automatically at boot
116
systemctl list-dependencies x.service
Command to list dependencies of a specific service
117
systemctl list-dependencies x.target
Command to list dependencies of a specific target
118
systemctl list-units
Command to list loaded units (services)
119
systemctl list-units --type service
Command to list loaded services
120
systemctl list-unit-files
Command to list installed unit files
121
/etc/systemd/
Directory containing systemd configuration files
122
/usr/lib/systemd/system/
Directory containing systemd unit files
123
/etc/systemd/system/
Directory containing user-created systemd unit files
124
/etc/systemd/system/default.target
Symbolic link to the default systemd target unit
125
/etc/systemd/system/multi-user.target.wants/
Directory containing symlinks to services that should be started when the system enters multi-user mode
126
/etc/systemd/system/multi-user.target
Symbolic link to the multi-user target unit
127
/etc/systemd/system/sysinit.target
Symbolic link to the sysinit target unit
128
/etc/systemd/system/basic.target
Symbolic link to the basic target unit
129
/etc/systemd/system/graphical.target
Symbolic link to the graphical target unit
130
^Z
Keyboard shortcut to suspend a process
131
^C
Keyboard shortcut to interrupt/terminate a process
132
^D
Keyboard shortcut to signal end-of-file (EOF)
133
&
Special character used for job control and running processes in the background
134
Process Attributes and States
Different states a process can be in: Running (R), Sleeping (S), Stopped (T), Dead (D), Idle (I), Zombie (Z)
135
Environment variables
Variables that define the environment in which a process runs
136
Standard input
Default input stream for a process
137
Standard output
Default output stream for a process
138
Standard error
Default error output stream for a process
139
Healthy Multiuser System
Maintaining system health and stability with multiple users
140
Regular Maintenance
Scheduled tasks and routines to ensure system reliability
141
Software Update with RHEL
Updating software packages and repositories with Red Hat Enterprise Linux (RHEL)
142
Usernames and UserIDs (UIDs)
Identifiers used to uniquely identify users on a Unix-like operating system
143
root account
Superuser account with administrative privileges
144
system accounts
Special user accounts used by system services and daemons
145
user accounts
Accounts created for individual users
146
Network Interface Names
Naming conventions for network interfaces
147
Security Best Practices
Best practices for ensuring system and network security
148
Public and Private Keys
Cryptographic keys used for authentication and encryption
149
File globbing
Pattern matching for file and directory names
150
Absolute and relative paths
Methods for specifying the location of files and directories
151
File formats
Formats and structures of commonly used system files
152
/etc/passwd
Format of the password file containing user account information
153
/etc/group
Format of the group file containing group account information
154
Importance of Software Updates
Importance of keeping software up to date to address security vulnerabilities and bugs
155
Concept of Package Management
Managing software installation, updates, and removal in a systematic manner
156
Dependency concept
Relationship between software packages and their dependencies
157
Package Managers
Tools used for installing, upgrading, configuring, and removing software packages
158
RPM Package Manager
Package management system used in Red Hat-based Linux distributions
159
chown command
Changes file ownership. The -R option recursively changes the ownership of a directory tree.
160
umask command
Displays or sets the default file permissions for newly created files.
161
Default umask values for Bash
Defined in /etc/login.defs and might be affected by settings in /etc/profile, /etc/bashrc, files in /etc/profile.d, or user's shell initialization files.
162
suid, sgid, and sticky bits
Special permissions providing additional access-related features to files.
163
Process
A running instance of an executable program, with states including running, sleeping, stopped, or zombie.
164
ps command
Lists processes running on the system.
165
Terminal Session
Each terminal has its own session, with a foreground process and independent background processes.
166
jobs command
Displays processes within a terminal session.
167
Signal
A software interrupt reporting events to an executing program.
168
kill command
Sends a signal to control processes.
169
pkill command
Sends a signal to control processes based on process names.
170
killall command
Sends a signal to control processes based on process names.
171
Load Average
An estimate of how busy the system is.
172
top command
Displays dynamic real-time information about running processes and system resource usage.
173
uptime command
Displays how long the system has been running and the average system load over different time intervals.
174
w command
Displays information about currently logged-in users and what they are doing, including load average.
175
systemd
Provides a method for activating system resources, server daemons, and other processes at boot time and on a running system.
176
systemctl start/stop/reload/enable/disable [service]
Commands used with systemctl to manage services, including starting, stopping, reloading, enabling, and disabling.
177
systemd utility
Used to manage service units, socket units, and path units.
178
systemctl status [unit]
Command used to determine the status of system daemons and network services started by the systemd utility.
179
systemctl list-dependencies [unit]
Command to list all service units that a specific service unit depends on.
180
Masking a service unit
systemd feature allowing a service unit to be masked so that it does not run, even to satisfy dependencies.
181
ssh command
Allows users to securely access remote systems using the SSH protocol.
182
Known Hosts files (~/.ssh/known_hosts and /etc/ssh/ssh_known_hosts)
Files where client systems store identities of remote servers.
183
SSH authentication types
Supports both password-based and key-based authentication methods.
184
ssh-keygen command
Generates an SSH key pair for authentication.
185
ssh-copy-id command
Exports the public key to remote systems for key-based authentication.
186
sshd service
Implements the SSH protocol on Red Hat Enterprise Linux systems.
187
/etc/ssh/sshd_config file
Configuration file for advanced SSH settings.
188
Recommended SSH configurations
Disable remote logins as root and require public key authentication instead of password-based authentication.
189
TCP/IP network model
A simplified, four-layered model describing how different protocols interoperate for sending traffic over the internet.
190
IPv4
The primary network protocol used on the internet today.
191
IPv6
Intended as a replacement for IPv4 network protocol.
192
Dual-stack mode
Red Hat Enterprise Linux operates using both IPv4 and IPv6 protocols simultaneously by default.
193
Network routes
Determine the correct network interface to send packets to a particular network.
194
NetworkManager daemon
Monitors and manages network configuration.
195
nmcli command-line tool
Configures network settings with the NetworkManager daemon.
196
Network configurations directory
In Red Hat Enterprise Linux 9, the default location is /etc/NetworkManager/system-connections.
197
System's static hostname
Stored in the /etc/hostname file.
198
hostnamectl command
Modifies or views the status of the system's hostname and related settings.
199
Red Hat Subscription Management
Provides tools for entitlements, updates, and tracking support contracts and subscriptions.
200
RPM packages
Software provided in RPM format for installation, upgrading, and uninstallation on the system.
201
rpm command
Can query local database for package information and install downloaded package files.
202
dnf utility
A powerful command-line tool for installing, updating, removing, and querying software packages.
203
Application Streams
Red Hat's feature to provide a single repository hosting multiple versions of application packages and dependencies.
204
For hardening purposes, what is the primary benefit of having the file /etc/shadow?
It stores encrypted user passwords, making them unreadable directly.
205
Which of the following represents the symbolic permission to give the owner read and write access, the group only read access, and others no access?
u=rw,g=r,o=-
206
If a Linux file has the permissions -rw-r--r--, who has the ability to write to the file?
Only the owner
207
Which of the following files contains encrypted passwords of users?
/etc/shadow
208
Setting the 's' bit on a file in the user ownership does which of the following:
All processes created using that file run with the user ownership of the command file
209
To be able to change into directory Dir1, what is the minimum permissions necessary for the Dir1 directory?
Execute (x)
210
What is the octal permission of a directory that allows the owner to access files if they know their names, but not to list or to change the file names?
100
211
Setting the 's' bit on a directory in the group ownership does which of the following:
All files created in that directory will have the same group ownership as the parent directory
212
The UID and GID for a user can be found in which file?
/etc/passwd
213
The /etc/group file contains information about:
Group memberships
214
For system hardening purposes, how can an administrator restrict a specific user from using the sudo command to gain superuser privileges?
Explicitly deny the user in the /etc/sudoers file or associated configurations.
215
In the context of Linux access controls, what does DAC stand for?
Discretionary Access Control
216
Setting the 's' bit on a file in the group ownership does which of the following:
All processes created using that file run with the group ownership of the command file
217
In an empty directory, you run the commands: touch ??? *** ; chmod 111 * chmod 444 ??? ; chmod 666 '***' ; chmod 333 * What permissions are on file ??? after above commands?
-wx -wx -wx
218
What is the octal mode of a directory that allows only the user to cd into it and list the names in it and create any new files?
700
219
Which command is used to change the ownership of a file in Linux?
chown
220
Which of the following commands is used to show the user's own identity and group information?
id
221
Which of the following commands can be used to change the ownership of a file in Linux?
chown
222
Which file in Linux contains the encrypted passwords of users?
/etc/shadow
223
Which command is used to modify an existing user's information in Linux?
usermod
224
Which of the following commands is used to change a user's default login shell?
chsh
225
In the file /etc/group, what does the last field represent?
List of users
226
What is the easiest way for root to allow a regular user in Red Hat Enterprise Linux to run any administrator commands with sudo?
Add the user to the wheel group
227
What value of umask gives the permissions below to a new file: rw-rw-r--
2
228
You are working at the Linux command line and your username is “homer”. You execute the command ls and see the following output: -rw-rw-r-- 1 homer homer 387 Nov 28 08:26 bigfoot -rwxr-xr-x 1 homer homer 1851882 Nov 28 08:26 dragon -rwxrwxr-x 1 homer homer 15957213 Nov 28 08:26 kraken What command can you type which will remove execute permission from the file dragon for all users except yourself?
chmod 744 dragon
229
Refer to the exhibit above. What would be the permissions of f1.txt after executing the last command?
700
230
When hardening a server system, which account should have its direct login access blocked?
Root user
231
In a Linux system, which account type is created for running specific services or applications?
System users
232
If an administrator wants to efficiently manage multiple users' default settings upon creation, which directory plays a critical role?
/etc/skel
233
What Linux command can be used to set the default permissions for all newly created files?
umask
234
Which command allows you to view the groups a user belongs to?
id
235
If an administrator wishes to prevent a specific user from using the sudo command, they should edit which file?
/etc/sudoers
236
What command is used to create a new group?
groupadd
237
To ensure a user cannot directly log into the system, which shell should be assigned in /etc/passwd?
/bin/nologin
238
In a multi-user GNU/Linux environment, which command is the safest to use when changing a user's default shell?
chsh
239
What Linux command can be used to change the group of a file?
chgrp
240
You are working at the Linux command line. What command can you type which will result in a new file being given the following permissions by default: - The file owner can read and write to the file, but not execute it. - Everyone other than the owner can read the file, but not write to or execute it.
umask 133
241
The filename /etc/passwd is a(n) _________________.
Absolute path
242
Which of the following is not true of the root user?
The root user can access any computer on the network.
243
Which Access Control Technique is based on security labels and is mandatory regardless of the user's wishes?
MAC
