Terminology Flashcards
1
Q
Describe $PATH
A
$PATH is a variable that contains a list of directories that are searched for executable files when a user enters a command.
2
Q
What does . (dot) represent in the command line?
Don’t confuse with the dot (.) regular expression.
A
. The current directory. Its value can be requested using the pwd command.
3
Q
What is an absolute filename?
A
A filename that is complete and starts with the name of the root directory, including all directories up to the current file or directory.
4
Q
In Linux what is an access control list (ACL)?
A
In Linux permissions, a system that makes it possible to grant permissions to more than one user and more than one group. Access control lists also allow administrators to set default permissions for specific directories.
5
Q
What is anacron?
A
A service that ensures that vital cron jobs can be executed when the server is down at the moment that the job normally should be executed. Can be considered an extension to cron.
6
Q
What does AND mean?
A
A logical construction that can be used in scripts. In an AND construction, the second command is executed only after successful execution of the first command.
7
Q
What is an application profile?
A
A collection of packages that may be used to install a specific version of software, according to a specific installation profile.
8
Q
What is an application stream?
A
A specific version of a dnf module that can be installed as such.
9
Q
What is the at utility?
A
A service that can be used to schedule future jobs for one-time execution.
10
Q
What is an **attribute **?
A
A property that can be set to a file or directory and that will be enforced no matter which user with access permission accesses the file.
For instance, a file that has the immutable (i) attribute set cannot be deleted, not even by the root user. However, the root user does have the capability to change the attribute, which would allow the root user to delete the file anyway.
11
Q
What is an audit log?
A
The main log file in /var/log/audit/audit.log, which by default contains all messages that are logged by the auditd service.
12
Q
What is auditd?
A
A service that runs by default on Red Hat Enterprise Linux and can be configured to log very detailed information about what is happening on RHEL.
Auditing is complementary to system logging and can be used for compliancy reasons. On RHEL, the auditing system takes care of logging SELinux-related messages, which makes it a relatively important system.
13
Q
What is autofs?
A
A service that takes care of automatically mounting file systems at the moment that a specific directory is accessed.
This service is very useful to ensure the automatic mounting of home directories for users in a centralized user management system, as can be implemented by the LDAP service.
14
Q
What is automount?
A
The process that is started by the autofs service. See autofs for more details.
15
Q
What is a background process?
A
A process that is running on a system without actively occupying a console.
Processes can be started in the background by adding a & after the command that starts the process. See also foreground process.
16
Q
What is a backup?
A
A copy of important data, which can be restored if at any point in time the original data gets lost.
17
Q
What is Bash?
A
The default shell that is used on Red Hat Enterprise Linux.
18
Q
What is Basic Input/Output System (BIOS)?
A
The first software that is started when a computer starts on older IBM-compatible computers.
Settings in the BIOS can be changed by using the BIOS setup program.
See also Unified Extensible Firmware Interface (UEFI).
19
Q
What is binary?
A
A numbering scheme that is based on bit values that can be on or off.
Binary numbers are 0 and 1. Because binary numbers are difficult to use, decimal, hexadecimal, or octal numbers often are used.
20
Q
What is a boot loader?
A
Program that is started as the very first thing while starting a computer and that takes care of loading the operating system kernel and initramfs.
21
Q
What is BtrFS?
A
A general-purpose Linux file system that is expected to become the default file system on Red Hat Enterprise Linux in a future release.
22
Q
What is bzip2?
A
A compression utility that can be used as an alternative to gzip.
23
Q
What is cache?
A
In memory management, the area of memory where recently used files are stored.
Cache is an important mechanism to speed up reads on servers.
24
Q
What does capability refer to?
A
A specific task that can be performed on Linux.
User root has access to all capabilities; normal users have access to limited sets of capabilities only.
25
What is a **certificate**?
In PKI cryptography, contains the public key of the issuer of the certificate. This public key is signed with the certificate of a certificate authority, which guarantees its reliability.
26
What is a **certificate authority (CA)**?
A commonly known organization that can be used to guarantee the reliability of PKI certificates.
The certificate authority provides a certificate that can be used to sign public key certificates. Instead of using commonly known organizations, self-signed certificates can be used for internal purposes as well.
27
What is **chrony**?
The service that offers **time synchronization service**s in Red Hat Enterprise Linux.
28
What is **chroot**?
An environment where a part of the file system is presented as if it were the root of the file system.
Chroot is used as a security feature that hides part of the operating system that is not required by specific services.
29
What is **CIFS**?
**Common Internet File System (CIFS) **
The standardized version of the Microsoft Server Message Block (SMB) protocol, which is used to provide access to shared printers, files, and directories in a way that is compatible with Windows servers and clients.
CIFS has become the de facto standard for file sharing in IT.
30
What is a **conditional loop**?
In shell scripting, a set of commands that is executed only if a specific condition has been met.
31
What is a **console**?
In Linux, the primary terminal where a user works. It is also a specific device with the name /dev/console.
32
What is a **container**?
A ready-to-run application that is started from an image and includes all application dependencies.
33
What is a **container engine**?
The code that allows containers to run on top of an operating system.
34
In SELinux, what is **context?**
In SELinux, a label that is used to define the security attributes of users, processes, ports, and directories. These contexts are used in the SELinux policy to define security rules.
35
In SELinux, what is a **context type**?
In SELinux, a label that identifies the SELinux properties of users, ports, and processes.
36
What is **CRI-o**?
| prounced CRY-o
The default container engine on RHEL 9.
| Pronounced CRY-o.
37
What is a **cron**?
A service that takes care of starting services repeatedly at specific times.
38
What is **deduplication **?
A storage technology that analyzes data to be stored on disk and takes out duplicate patterns to allow for more efficient storage.
39
What is **dependency hell**?
Situation where for package installation, other packages are needed, which by themselves could require dependencies as well. The problem of dependency hell has been fixed by the introduction of repository-based systems.
40
In rsyslog, what is a **destination**?
In rsyslog, the place where log messages should be sent by the logging system.
Destinations are often files, but can also be input modules, output modules, users, or hosts.
41
What is a **device file**?
A file that is created in the /dev directory and that is used to represent and interact with a device.
42
What is a **device mapper**?
A service that is used by the Linux kernel to communicate with storage devices.
Device mapper is used by LVM, multipath, and other devices, but not by regular hard disks. Device files that are created by device mapper can be found in the /dev/mapper directory.
43
What is **dmesg**?
dmesg is a utility that can be used to read the kernel ring buffer, which contains log messages that were generated by the Linux kernel.
44
What is **dnf**?
dnf is the new software manager that replaces the yum utility in RHEL 9.
45
What is **Docker**?
A common solution to run containers. Docker was the default container solution in RHEL 8 but is no longer supported and was replaced with CRI-o/podman in RHEL 9.
46
What is **dracut**?
dracut is a utility used to generate the initramfs, an essential part of the Linux operating system that contains drivers and other vital files required to start a Linux system.
47
In RHEL what is **enforcing mode**?
The SELinux mode where SELinux is fully operational and applies all restrictions that have been configured for a specific system.
48
What does the term **environment** mean?
The collection of settings that users or processes are using to do their work.
49
What is **epoch time**
In Linux, the number of seconds that have passed since epoch (corresponds to midnight on January 1, 1970). Some utilities write epoch time instead of real clock time.
Epoch time is also know as unix time.
50
What is **escaping**?
In a shell environment, using special syntax to ensure that specific characters are not interpreted by the shell.
Escaping may be necessary to show specific characters onscreen or to ensure that regular expression metacharacters are not interpreted by the bash shell first.
51
What is the **exec** command used for?
Exec is a system call that replaces the current process with another one; this command does not create a new process, it just replaces the bash with the command to be executed. If the exec command is successful, it does not return to the calling process
See also fork.
52
In NFS what is **export**?
In NFS, a directory that is shared on an NFS server to allow access to other servers.
53
What are the three **Ext** file system version?
**Ext2, Ext3, and Ext4**
Up to RHEL 6, Ext4 was the default file system. It is now considered inadequate for modern storage needs, which is why Ext4 in RHEL 7 was replaced by XFS as the default file system.
54
What is an **extended partition**?
A solution to create more than four partitions on an MBR disk.
55
What is an **external command**?
A command that exists as a file on disk.
56
In rsyslogd what is **facility**?
**facility** in rsyslogd is the source where log information comes from.
A strictly limited number of facilities have been defined in rsyslogd.
57
What is **FHS**?
**Filesystem Hierarchy Standard (FHS)** A standard that defines which Linux directories should be used for which purpose. Read man 7 file-hierarchy for a specification of the FHS.
58
What is a **file descriptor**?
A pointer that is used by a Linux process to refer to files that are in use by the process.
59
What is the default management tool for firewall rules in RHEL?
**firewalld** is the modern service (replacing iptables) that is used since RHEL 7 to implement firewalling based on the Linux kernel firewalling framework.
60
What is a **foreground process**?
A process that is running on a system and occupies the console it is running on.
Linux processes that are started by users can be started in the foreground or in the background. If a process has been started as a foreground process, no other processes can be started in the same terminal until it finishes or is moved to the background.
See also background process.
61
What does **fork** mean when refering to processes?
A system call that starts a new process as a child of the current process.
This is the default way commands are executed.
See also exec.
62
What is **fstab**?
**fstab** a configuration file that is used on Linux to mount file systems automatically when the system starts.
| [An intro to /etc/fstab file](https://www.redhat.com/sysadmin/etc-fstab)
63
What is a **hard link**?
A name associated with an inode. Inodes are used to store Linux files.
An inode contains the complete administration of the file, including the blocks in which the file is stored. A file that does not have at least one hard link is considered a deleted file. To increase file accessibility, more than one hard link can be created for an inode.
64
What is **hardware time**?
The time that is provided by computer hardware, typically the BIOS clock.
65
What is **init**?
The first process that is started once the Linux kernel and initramfs have been loaded.
From the init process, all other processes are started. As of RHEL 7, the init process has been replaced by Systemd.
66
What is **initramfs**?
The initial RAM file system. Contains drivers and other files that are needed in the first stages of booting a Linux system.
On Red Hat Enterprise Linux, the initramfs is generated during installation and can be manually re-created using the dracut utility.
67
What is **inode**?
A structure that contains the complete administration of a file.
Every Linux file has an inode, and the inode contains all properties of the file but not the filename.
68
In rsyslog, what is an **input module**?
In rsyslog, an input module allows rsyslog to receive log messages from specific sources.
69
What is an **internal command**?
An **internal command** is a part of the shell and does not exist as a file on disk.
70
What is **iptables** used for?
iptables is an older solution to create firewall rules on the Linux operating system. As of RHEL 7, iptables has been replaced by firewalld.
It interfaces with the netfilter Linux kernel firewalling functionality and was the default solution to create software firewalls on earlier versions of RHEL.
71
What is **journalctl**?
The command used to manage systemd-journald.
72
What is **journald**?
systemd-**journald** is the part of Systemd that takes care of logging information about events that have been happening.
The introduction of journald ensures that information about all services can be logged, regardless of how the service itself is configured to deal with information that is to be logged.
73
What is the linux **kernel**?
**kernel** is the central component of the operating system.
It manages I/O requests from software and translates them into data processing instructions for the hardware in the computer.
74
What is the **kernel ring buffer**?
The **kernel ring buffer** is a part of memory where messages that are generated by the kernel are stored.
The dmesg command enables you to read the contents of the kernel ring buffer.
75
What is **kernel space**?
**kernel space** is the part of memory that is reserved for running privileged instructions.
Kernel space is typically accessible by the operating system kernel, kernel extensions, and most device drivers. Applications normally run in user space, which ensures that a faulty application cannot crash the computer system.
76
What does **KVM** stand for?
**Kernel-based Virtual Machine (KVM)**
The Linux kernel module that acts as a hypervisor and makes it possible to run virtual machines directly on top of the Linux kernel.
77
What is the **kill** command?
**kill** is a command that can be used to send a signal to a Linux process. Many signals are defined (see man 7 signal), but only a few are commonly used, including SIGTERM and SIGKILL, both of which are used to stop processes.
78
Within the file system, what is a **label**?
A **label** is a name that can be assigned to a file system.
Using labels can be a good idea, because once a label is assigned, it will never be changed, which guarantees that the file system can still be mounted, even if other parameters such as the device name have changed.
However, UUIDs are considered safer than labels because the chance of having a duplicate label by accident is much higher than the chance of having a duplicate UUID. See also universally unique ID (UUID).
79
In regex what is a **line anchor**?
line anchor in regular expressions is a character that refers to a specific position in a line.
80
In systemd what is **linger**?
**linger** is the Systemd feature that is needed to start Systemd user units at system boot and not at user login.
81
What is a **logical extent**?
**logical extent** is the building block that is used in LVM to create logical volumes.
It normally has a size of a few megabytes that corresponds to the size of the physical extents that are used.
82
What is a **logical partition**?
**logical partition** A partition that is created in an extended partition. See also extended partition.
83
What is a **logical partition**?
**logical partition** A partition that is created in an extended partition. See also extended partition.
84
What does **LVM** stand for?
**Logical Volume Manager (LVM)**
The software that makes it possible to work with logical volumes.
85
What is the **login shell**?
**login shell**
The shell that is opened directly after a user has logged in.
86
What does **MBR** stand for?
**Master Boot Record (MBR)**
On a BIOS system, the first 512 bytes on the primary hard disk. It contains a boot loader and a partition table that give access to the different partitions on the hard disk of that computer.
87
In **DNF** what is a **module**?
A collection of software packages that can be managed as one entity and can contain different versions of a software solution.
88
What is a **namespace**?
A namespace is an isolated environment that is created by the Linux kernel and allows for running containers in complete isolation.
Namespaces exist for multiple aspects of the operating system, including mounts, processes, users, and more.
89
What is a **netfilter**?
The netfilter is the part of the Linux kernel that implements firewalling.
90
What does **NFS** stand for?
**Network File System (NFS)**
A common UNIX solution to export physical file systems to other hosts on the network. The other hosts can mount the exported NFS directory in their local file system.
91
What are **nftables**?
nftables are the service that manages kernel firewalling.
It is a replacement of the older iptables service.
92
What is the **nice** command used for?
The nice command lets you run a command at a priority lower than the command's normal priority.
A negative nice value will make the process more aggressive, giving it a higher priority (which is expressed by a lower priority number); a positive nice value will make a process less eager so that it gives priority to other processes.
93
What is the **octal** numeral system?
octal is numbering scheme that uses the numbers 0 through 7 only.
Used when working with Linux permissions using the umask setting or the chmod command.
94
In the Linux file system what is **ownership**?
ownership In file system permissions, the basis of the effective permissions that a user has. Every file has a user owner and a group owner assigned to it.
95
What is a **package**?
A **package** is a bundle that is used to distribute software. A package typically contains a compressed archive of files and metadata that includes instructions on how to install those files.
96
What is a **package group**?
A package group is a group of packages that can be installed as such using the dnf groups install command.
97
In DNF what is a **package group**?
In package group (in dnf) is a group of software packages that can be installed with a single command.
| DNF or Dandified YUM
98
What is a **pager** program?
pager is a program that can be used to browse page by page through a text file.
The less utility provides one of the most common Linux pagers.
99
What is the **parent shell**?
The parent shell is the environment from which a shell script or program is started. Processes or child scripts will inherit settings from the parent shell.
100
In SELinux what is **permissive mode**?
permissive mode is the SELinux mode where nothing is blocked but everything is logged in the audit log. This mode is typically used for troubleshooting SELinux issues.
101
What is a **physical extent**?
A physical extent is the physical building block that is used when creating LVM physical volumes.
Typically, the size is multiple megabytes.
102
What is a **physical volume**?
A physical volume is the foundation building block of an LVM configuration.
The physical volume typically corresponds to a partition or a complete disk device.
103
What does **PID** stand for?
process identification number
104
What is a **pipe**?
A pipe Is a structure that can be used to forward the output of one command to be used as input for another command.
105
What is **POSIX**?
**Portable Operating System Interface (POSIX)**
A standard that was created to maintain compatibility between operating systems. The standard mainly applies to UNIX and guarantees that different flavors of Linux and UNIX are compatible with one another.
106
What is the **portmapper**?
portmapper (Remote Procedure Call)
A Remote Procedure Call service that needs to run on systems that provide RPC services.
Portmapper uses dynamic ports that do not correspond to specific TCP or UDP ports; the service will pick a UDP or TCP port that will be used as long as the process is active.
When the process is restarted, chances are that different ports are used. They need to be mapped to fixed UDP and TCP ports in order to make it possible to open the firewall for these ports. Portmapper is still used by components of the NFS service.
107
What is a **primary group**?
A primary group the group that is listed in the group membership field for a user in /etc/passwd.
Every Linux user is a member of a primary group. Apart from that, users can be made a member of secondary groups as well.
108
What is the **primary partition**?
The primary partition in MBR, one of a maximum of four partitions that can be created in the Master Boot Record. See also extended partition.
109
What is does **priority** mean in process handling?
priority (in process handling) Specifies the importance of a process.
Process priority is expressed with a number (which can be modified using nice). Processes with a lower priority number are serviced before processes with a higher priority number.
110
What is does **priority** mean in rsyslog?
In rsyslog, priority is used to specify the severity of a logged event.
Based on the severity, specific actions can be taken.
111
What is **proc**?
proc is a kernel interface that provides access to kernel information and kernel tunables. This interface is available through the /proc file system.
112
What is a **process**?
A process is a task that is running on a Linux machine. Roughly, a process corresponds to a program, although one program can start multiple processes.
113
What is a **process identification number (PID)**?
process identification number (PID) is a unique number that is used to identify a process running on a Linux system.
114
In **tuned** what is a **profile**?
A profile in tuned, a collection of performance settings that can easily be applied.
Tuned is a Linux feature that monitors a system and optimizes its performance under certain workloads.
115
What does PV stand for?
Physical volume
116
What does **RTC** stand for?
**real-time clock (RTC)**
The hardware clock that is installed on the computer motherboard.
117
What does the **reboot** command do?
reboot is the procedure of stopping the computer and starting it again.
118
What does **RPM** stand for?
**Red Hat Package Manager (RPM)**
The name for the package format that is used on RHEL for software packages and for the Package Management software. RPM has become the standard for package management on many other Linux distributions as well.
119
What is a **reference clock**?
A reference clock is a clock that is used as a time source in an NTP time configuration.
Typically, a reference clock is a highly reliable clock on the Internet, but it can be an internal clock on the computer’s motherboard as well.
120
What is a **regular expression**?
A regular expression is a search pattern that allows users to search text patterns in a flexible way.
Not to be confused with shell metacharacters.
121
What is a **relative filename**?
A relative filename is a filename that is relative to a directory that is not the root directory.
122
What is a **Remote Procedure Calls (RPC)**?
**Remote Procedure Calls (RPC)**
A method for interprocess communication that allows a program to execute code in another address space. Remote Procedure Calls is an old protocol and as such is still used in the Network File System.
123
What is a **repository (repo)**?
A repository is an installation source that contains installable packages and an index that contains information about the installable packages so that the installation program dnf can compare the version of packages currently installed with the version of packages available in the repository.
124
What is **rsyslogd**?
rsyslogd is the generic daemon that logs messages.
125
What is **samba**?
Samba is the name for the Linux service that implements the SMB protocol.
126
What is the **scheduler**?
The scheduler is the part of the Linux kernel that monitors the queue of runnable processes and allocates CPU time to these processes.
127
What is a **secondary group**?
The secondary group is a group that a user is a member of but which membership is not defined in the /etc/passwd file.
When new files are created, the secondary group will not automatically become the owner of those files.
128
What does **SSH** stand for?
**Secure Shell (SSH) **
A solution that allows users to open a shell on a remote server where security is implemented by using public/private key cryptography.
129
What **SELinux**?
SELinux is a Linux kernel security module that provides a mechanism for supporting access control security policies.
130
What is a **SELinux Policy**?
**SELinux Policy**
The collection of rules that is used to define SELinux security.
131
What does **SMB** stand for?
**Server Message Block (SMB)**
An application-level protocol that is used to provide shared access to files, printers, and serial ports, which on Linux is implemented in the Samba server.
132
In **firewalld** what does **service** mean?
service (in firewalld) is a configuration of firewall settings that is used to allow access to specific processes.
133
In **systemd** what are **services**?
in Systemd services are processes that need to be started to provide specific functionality.
134
What is **shebang**?
A shebang starts with a #, which is followed by a ! and the complete pathname of the shell, such as #!/bin/bash.
The characters used in a script to indicate which shell should be used for executing the code in the shell script. If no shebang is used, the script code will be interpreted by the parent shell, which may lead to errors in some cases.
135
What is the **shell**?
The **shell** is the environment from which commands can be executed. Bash is the default shell on Linux, but other shells exist as well.
136
What are **shell metacharacters**?
shell metacharacters are characters such as `
*, ?, and [a-z]
`
that allow users to refer to characters in filenames in a flexible way.
137
What is a **signal**?
A signal is an instruction that can be sent to a process.
Common signals exist, such as SIGTERM and SIGKILL, but the Linux kernel allows a total of 32 different signals to be used. To send a signal to a process, use the kill command.
138
What is **software time**?
**software time / system time**
The time that is maintained by the operating system. When a Linux system boots, system time is set to the current hardware time, and while the operating system is running, it is often synchronized using the Network Time Protocol (NTP).
139
In **SELinux** what is **source context**?
In SELinux source context is the context of the processes or users that initiate an action.
A context in SELinux is a label that identifies allowed operations. Everything in an SELinux environment has a context.
140
What does **STDERR** mean?
standard error (STDERR) The default location where a program sends error messages.
141
What does **STDIN** mean?
standard input (STDIN) The default location where a program gets its input.
142
What does **STDOUT**?
standard output (STDOUT) The default location where a program sends its regular output.
143
What is **star**?
star A legacy extended version of tar, which offers support for extended attributes. Currently no longer required, as all of its functionality has been integrated in tar.
144
What is **Stratis**?
**Stratis** is the new volume managing file system that was introduced in RHEL 8.
145
What is the **subshell**?
The subshell is a shell that is started from another shell. Typically, a subshell is started by running a shell script.
146
What is a **symbolic link**?
symbolic link is a special type of file that contains a reference to another file or directory in the form of an absolute or relative path.
147
What is **sysfs**?
sysfs is the kernel interface that is mounted on the /sys directory and which is used to provide access to parameters that can be used for managing hardware settings.
148
What is a **system call**?
system call is a low-level operating system instruction.
149
What is **system time**?
system time is the time that is maintained by the operating system.
When a Linux system boots, system time is set to the current hardware time, and while the operating system is running, it is often synchronized using the Network Time Protocol (NTP).
150
What is **systemd**?
Systemd is the service manager on RHEL 9.
Systemd is the very first process that starts after the kernel has loaded, and it takes care of starting all other processes and services on a Linux system.
151
What is **systemd-journald**?
systemd-journald is the part of Systemd that takes care of logging information about events that have been happening.
The introduction of journald ensures that information about all services can be logged, regardless of how the service itself is configured to deal with information that is to be logged.
152
What is a **tainted kernel**
A **tainted kernel** is a kernel in which unsupported kernel modules have been loaded.
[Tainted kernels](https://docs.kernel.org/admin-guide/tainted-kernels.html)
153
What does **tar** stand for?
The **Tape Archiver**; the default Linux utility that is used to create and extract backups.
154
In Systemd what is a **tartget**?
In Systemd a target, is a collection of unit files that can be managed together.
155
In **SELinux** what is **target context**?
In SELinux, target context is the context that is set to a target object, such as a port, file, or directory.
156
What is a **terminal**?
**terminal**
Originally, the screen that was used by a user to type commands on.
On modern Linux systems, pseudo terminals can be used as a replacement. A pseudo terminal offers a shell window from which users enter the commands that need to be executed.
157
What is **thin allocation**?
**thin allocation**
In storage, an approach that enables the system to present more storage to the storage user than what is really available by using smart technologies to store data, like deduplication.
158
What is a **thread**?
A thread is a subdivision of a process.
Many processes are single threaded, which means that process is basically one entity that needs to be serviced.
On a multicore or multi-CPU computer system, working with multithreaded processes makes sense.
That way, the different cores can be used to handle the different threads, which allows a process to benefit from multicore or multithreaded environments.
159
What is **time synchronization**?
time synchronization is a system that ensures that multiple servers are using the exact same time.
To accomplish time synchronization, it is common to use an external time server, as defined in the Network Time Protocol (NTP).
160
What is the **timer** command used for?
timer is a Systemd unit type that can be used as an alternative to cron jobs and run units at a specific time.
161
What does **TLS** stand for?
**Transport Layer Security (TLS) **
A cryptographic protocol that is created to ensure secured communications over a computer network. In TLS, public and private keys are used, and certificates authenticate the counterparty.
TLS was formerly known as SSL.
162
What is **TTY**?
TTY is a program that provides a virtual terminal on Linux.
Every terminal still has a TTY name, which is either tty1-6 for virtual TTYs or /dev/pts/0-nn for pseudo terminals.
TTY stands for "teletypewriter.
163
What is **tuned**?
tuned is a service on RHEL that enables administrators to easily apply performance settings by using profiles.
164
What is **udev**?
udev is a service that works with the Linux kernel to initialize hardware.
165
What does **UEFI** stand for?
**Unified Extensible Firmware Interface (UEFI)**
A replacement of the Basic Input/Output System used on older IBM-compatible computers as the first program that runs when the computer is started. UEFI is the layer between the operating system and the computer firmware.
166
What is **umask**?
umask is an octal value that defines the default permissions as a shell property.
167
What does the **umount** command do?
umount is the command that is used to decouple a file system from the directory on which it is mounted.
168
What is a **unit**?
unit is an item that is managed by Systemd.
Different types of units exist, including service, path, mount, and target units.
169
What does **UUID** stand for?
**universally unique ID (UUID)** is an identification number consisting of a long random hexadecimal number that is globally unique.
170
What is an **unprivileged user**?
unprivileged user is a regular non-root user account to which access restrictions apply, as applied by permissions.
171
What is the definition of a **user**?
A user is an entity that is used on Linux to provide access to specific system resources.
Users can be used to represent people, but many services also have a dedicated user account, which allows the service to run with the specific permissions that are needed for that service.
172
What is **user space**?
user space is the area of memory that is accessible by application software that has been started with non-root privileges.
173
What does **UTC** stand for?
Coordinated Universal Time.
174
What is a **value**?
value is the data that is assigned to a specific property, variable, or record.
175
What is a **variable**?
variable is a label that contains a specific value that can be changed dynamically. In scripting, variables are frequently used to allow the script to be flexible.
176
What is **VFAT**?
VFAT is the Linux kernel driver that is used to access FAT-based file systems.
FAT is a commonly used file system in Windows environments. The Linux VFAT driver allows usage of this file system.
177
What does **VG** stand for?
**volume group (VG)**
The abstraction layer that in Logical Volume Manager is used to represent all available storage presented by physical volumes from which logical volumes can be created.
178
In systemd what are **wants**?
want is an indication for a Systemd unit file that it is supposed to be started from a specific Systemd target.
Wants= A weaker version of Requires=. Units listed in this option will be started if the configuring unit is.
However, if the listed units fail to start or cannot be added to the transaction, this has no impact on the validity of the transaction as a whole.
179
What is **XFS**?
XFS is a high-performance 64-bit file system that was created in 1993 by SGI and which in RHEL 9 is used as the default file system.
180
What is **Xz**?
Xz is a compression utility that can be used as an alternative to gzip or bzip2.
181
What is **YUM**?
**Yellowdog Update, Modified** the full name for **Yum**, the meta package handler that on older versions of RHEL was used to install packages from yum repositories.
Now replaced with dnf.
182
What is a **zombie** process?
A zombie is a process that has lost contact with its parent and for that reason cannot be managed using regular tools.
183
In **firewalld** what is a **zone**?
zone In firewalld, a collection of one or more network interfaces that specific firewalld rules are associated with.
