CompTIA Server+ (SK0-005) flashcards

A Disk I/O bottleneck occurs when the storage subsystem cannot process read/write requests fast enough, leading to high wait times and reduced application performance.

• Characterized by high disk I/O wait times.
• CPU and memory utilization often remain normal.
• Common in database servers or applications with heavy disk access.
• Can be resolved by faster disks (SSDs), RAID optimization, or increasing disk controllers.

Memory trick: Imagine a server like a highway; if one lane (disk) is jammed, everything slows down.

A database connection timeout occurs when a client application attempts to establish a connection to a database server but the server does not respond within a specified time limit.

• Can be caused by network latency, firewall, or server overload.
• Successful ping/telnet often points to server-side resource issues.
• Requires examining database server performance metrics.

Memory trick: Timeout means server's too tired to talk.

Significant slowdown in a RAID 5 array's read/write operations, often caused by a single failing or degraded drive, even if the array is still functional.

• RAID 5 can operate with one failed drive, but performance is severely impacted.
• A 'failing' drive might not be completely dead but struggling, causing high latency and retries.
• Monitoring individual drive health and I/O statistics is crucial for early detection.

Memory trick: RAID 5: One slow drive makes the whole array a snail!

An enterprise-grade point-to-point serial protocol that connects storage devices (HDDs/SSDs) to servers, offering higher performance, scalability, and reliability than SATA.

• Supports dual-porting for redundancy
• Uses SCSI command set
• Backward compatible with SATA drives (SAS HBA can connect to SATA drives)

Memory trick: SAS is king for enterprise speed, SATA for home, NVMe for ultimate need.

A diagnostic screen displayed by VMware ESXi upon encountering a critical error, indicating a kernel panic or unrecoverable system failure, often due to hardware issues.

• Analogous to a Windows Blue Screen of Death (BSOD).
• Common causes include faulty RAM, CPU issues (overheating, unsupported features), driver bugs, or storage controller problems.
• Memory-related issues (incompatibility, faulty modules) are a very frequent cause, especially after upgrades.
• Requires analysis of the PSOD message and log files for deeper diagnosis.

Memory trick: Purple Screen? Your ESXi host is in a 'Memory' Maze!

Software licensing compliance refers to adhering to the terms and conditions of software licenses, ensuring that an organization has the legal right to use all installed software according to the vendor's agreements.

• Avoids legal penalties and fines
• Requires accurate asset tracking
• Can involve per-device, per-user, or per-core models

Memory trick: License compliance: Count your copies, buy your rights, avoid the fines!

A Microsoft Management Console (MMC) snap-in that allows users to view event logs on a local or remote machine.

• Logs application, security, system, and setup events.
• Essential for troubleshooting and auditing.
• Events contain details like date, time, source, and event ID.

Memory trick: Events tell the story of the server's day.

A standardized client-server interface that allows a computer to boot directly from a network interface, independent of data storage devices or installed operating systems.

• Enables network-based OS installation.
• Requires a DHCP server and a TFTP server.
• Commonly used for bare-metal provisioning.

Memory trick: Network Prep eXactly for Everything

A fully equipped, operational, and geographically separate facility that replicates the primary data center, allowing for immediate switchover with minimal RTO and RPO in a disaster.

• Highest cost, lowest RTO/RPO.
• Fully operational with mirrored data.
• Allows for near-instant failover.

Memory trick: Hot is ready, Warm needs warming, Cold is just a shell.

A set of processes and tools used to identify, acquire, test, and deploy software updates (patches) to maintain consistency, security, and stability across an organization's systems.

• Automates patch deployment.
• Ensures compliance and security.
• Reduces manual effort and errors.

Memory trick: Centralized Control, Consistent Code

RAID Level 5 is a striped set with distributed parity. It provides fault tolerance and improved performance by distributing both data and parity information across multiple disk drives.

• Requires a minimum of 3 disks
• Can sustain a single disk failure
• Good for read-heavy workloads

Memory trick: Redundant Array of Independent Disks: Reliability And Immediate Data Protection!

IT Asset Management (ITAM) is a set of business practices that joins financial, contractual, and inventory functions to support life cycle management and strategic decision making for the IT environment.

• Tracks hardware, software, and licenses
• Supports budgeting and procurement
• Ensures compliance and optimizes costs

Memory trick: ITSM: Managing assets, changes, incidents, and problems helps keep the business flowing!

The process by which the server's firmware (BIOS/UEFI) allocates a portion of system RAM for hardware components like integrated graphics or other system functions before the operating system takes control.

• Performed during POST (Power-On Self-Test)
• Often configurable in firmware settings
• Reduces usable RAM for the operating system

Memory trick: Firmware sets the stage, then OS takes the page, CPU controls the flow, RAM is where data will go.

A cryptographic network protocol for operating network services securely over an unsecured network.

• Provides secure remote shell access.
• Encrypts all communication.
• Used for command execution, file transfer (SCP/SFTP), and tunneling.

Memory trick: SSH is the secure key to remote server doors.

When a system runs out of physical RAM and resorts to using a portion of the hard drive (swap space) as virtual memory, leading to severe performance degradation.

• Causes high disk I/O activity and long I/O wait times.
• Results in significantly slower application launches and overall system responsiveness.
• Indicates a need for more physical RAM or optimized memory usage.

Memory trick: Slow server, disk light glows, RAM's low, where swap space goes!

Apache Virtual Hosts allow a single web server to host multiple websites or domains, each with its own distinct configuration, document root, and often its own set of resources.

• Can be IP-based (different IP addresses) or Name-based (different hostnames on the same IP).
• Enables efficient use of server resources for multiple web properties.
• Each virtual host can have its own log files and configuration directives.

Memory trick: Virtual Hosts Handle Diverse Websites Easily.

A security model where the operating system restricts a subject's (e.g., process) ability to access or perform any operation on an object (e.g., file) based on security labels.

• System-enforced, users cannot override these policies.
• Provides a strong defense against privilege escalation and compromised processes.
• Examples include SELinux (Linux) and AppArmor (Linux).

Memory trick: Process Control: MAC is the 'Mandatory' Guardian!

A high-density server memory module that uses a memory buffer chip to isolate command, address, and data lines from the memory controller, allowing more ranks and higher total capacity per DIMM than RDIMM.

• Buffers data lines in addition to command/address (unlike RDIMM)
• Enables highest memory density and capacity in servers
• Slightly higher latency than RDIMM due to buffering

Memory trick: LRDIMM 'loads off' extra weight from every line, even data, to pack in more memory.

The process of replacing a power supply unit in a server while the server remains powered on and operational, relying on redundant power sources.

• Requires redundant PSUs (N+1 or N+N).
• Primary goal is to maintain server uptime.
• Crucial to verify remaining PSU functionality before removal.

Memory trick: Before you 'swap', make sure the 'other' one is 'running'!

The primary configuration file on Debian and its derivatives for defining network interface settings.

• Located at `/etc/network/interfaces`.
• Used for static IP, DHCP, gateway, and DNS settings.
• Requires network service restart or reboot to apply changes.

Memory trick: Interfaces define how the network interacts.

A duplex mismatch occurs when two connected network devices (e.g., a server NIC and a switch port) are configured with different duplex settings (one full-duplex, one half-duplex).

• Leads to severe performance degradation and high error rates.
• Commonly causes late collisions on half-duplex side.
• Often results in retransmissions and slow network speeds.

Memory trick: Duplex drama: half vs. full, a network duel.

Troubleshooting network connectivity often starts with checking physical components like cables, connectors, and link lights, as these are common points of failure.

• Loose or damaged cables can cause intermittent connectivity.
• Link lights provide immediate visual feedback on physical connection status.
• Physical layer issues must be resolved before moving to higher-layer troubleshooting.

Memory trick: Always check the physical connection first; a loose cable can't be ignored.

The combination of GUID Partition Table (GPT) partitioning scheme and Unified Extensible Firmware Interface (UEFI) boot mode is necessary to fully utilize and boot from hard drives larger than 2TB.

• GPT supports drives > 2TB
• UEFI is the modern boot firmware
• MBR/Legacy BIOS are limited to 2TB

Memory trick: UEFI and GPT for big drives, BIOS and MBR for old lives.

A warning from a RAID controller or drive monitoring system (like S.M.A.R.T.) indicating that a drive is likely to fail in the near future, based on detected errors or degrading performance metrics.

• The drive has not yet failed, and the array may still be redundant.
• Indicates a high risk of imminent failure.
• Requires proactive replacement and data protection measures.

Memory trick: Drive's warning, array's still fine? Backup first, then draw the line!

Manually assigning network parameters (IP, gateway, DNS) to a network interface on a Linux server.

• Ensures consistent network identity.
• Requires specific configuration files based on distribution.
• Overrides DHCP settings if configured.

Memory trick: Interfaces define the network's face, resolv tells names where to race.

The document root is the directory on a web server where web content (HTML, images, etc.) is stored and served from.

• Must exist and be accessible by the web server process.
• Typically specified in the Apache configuration file (httpd.conf/apache2.conf).
• Common default locations include /var/www/html or /srv/www.

Memory trick: Root folder missing, web server's fizzing.

A suite of protocols that provides cryptographic security, including authentication and encryption, for communication over an Internet Protocol (IP) network.

• Operates at the network layer (Layer 3).
• Used to create secure VPN tunnels.
• Provides confidentiality, integrity, and authenticity.

Memory trick: IPsec secures the entire IP packet, not just the application.

A command-line utility used to control the systemd system and service manager, which is the default init system for most modern Linux distributions.

• Manages services, units, and targets.
• Enables/disables services at boot.
• Replaced SysVinit and Upstart tools.

Memory trick: System Control, Start Smart

A RAID level that provides fault tolerance against two simultaneous drive failures by using two independent parity blocks distributed across all drives in the array.

• Minimum 4 drives
• N-2 usable capacity
• High fault tolerance, good performance

Memory trick: RAID 0 is fast, RAID 1 mirrors past, RAID 5 one parity, RAID 6 two drives last.

An open, vendor-neutral, industry-standard application protocol for accessing and maintaining distributed directory information services.

• Used for centralized identity and access management.
• Stores user accounts, groups, and network resources.
• Commonly used with Active Directory and OpenLDAP.

Memory trick: LDAP is the phone book for users and their permissions.

The process of dividing a physical server into multiple isolated virtual servers (virtual machines), each capable of running its own operating system and applications.

• Maximizes hardware utilization.
• Provides isolation between applications/OSes.
• Simplifies server provisioning and management.

Memory trick: Virtualize for Value

In a RAID 1 (mirroring) array, one drive can fail without causing data loss or interruption to server operation due to data redundancy.

• Server remains operational with one failed drive.
• Redundancy is lost until the drive is replaced.
• Hot-swapping is often supported to replace the drive without downtime.

Memory trick: One drive down? RAID 1's crown: hot-swap it, no server frown!

Circuit breakers protect electrical circuits by tripping and cutting power when the current exceeds a safe limit, often due to a sustained or transient overload from connected devices.

• Rated for maximum current flow.
• Trip when current exceeds rating, even momentarily.
• Continuous loads should ideally not exceed 80% of breaker capacity to prevent nuisance trips.

Memory trick: If the power keeps cutting, the breaker's likely strutting its stuff too much.

A Windows security feature that helps prevent unauthorized changes to the operating system by prompting for administrative approval, even for administrators, when attempting actions that require elevated privileges.

• Restricts even administrator accounts by default.
• Requires elevation for certain system-level actions.
• Can interfere with applications expecting full administrator rights.

Memory trick: Access denied, even as admin? UAC's probably trying to win.

An error message indicating that the server actively denied an SSH connection attempt, often because the SSH service is not running or a firewall is blocking it.

• Implies network connectivity to the server exists.
• Often points to issues with the SSH daemon (sshd) service.
• Could also be a server-side firewall blocking port 22.

Memory trick: SSH no go? Check the daemon, let the service flow!

Lightweight Directory Access Protocol; an open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services.

• Hierarchical structure.
• Centralized identity management.
• Widely compatible (e.g., Active Directory, OpenLDAP).

Memory trick: LDAP is like a 'library' for users and their info.

MPMs are modules that determine how Apache handles client requests, managing network connections, and dispatching requests to handler processes or threads.

• Different MPMs are optimized for different workloads and server architectures.
• Common MPMs include prefork, worker, and event.
• Choosing the right MPM can significantly impact server performance and resource utilization.

Memory trick: Many Processes Manage Efficient Traffic.

A firmware command for solid-state drives (SSDs) that permanently erases all data blocks, making data irrecoverable.

• Specific to flash-based storage.
• Overcomes wear-leveling complexities.
• Different from traditional HDD wiping.

Memory trick: SSDs need a 'secure' wipe, magnets don't work right.

The SSH daemon (sshd) is the server-side component that listens for and handles incoming SSH connections on a Linux system. If it's not running or misconfigured, SSH connections will fail.

• Responsible for accepting SSH connections.
• Listens on port 22 by default.
• Can be checked using 'systemctl status sshd' or 'service sshd status'.
• Configuration file is typically '/etc/ssh/sshd_config'.

Memory trick: If the door won't open, check if the doorkeeper (daemon) is there and has the right key.

DCOM error 10016 is a common Windows event log entry indicating that a specific COM component tried to launch or activate without the necessary permissions for a particular user or service.

• Often seen with application crashes or failures to start.
• Indicates a permission issue with Distributed Component Object Model (DCOM) components.
• Resolved by modifying security permissions for the specific COM component in 'Component Services'.
• Usually involves granting Local Launch, Local Activation, Remote Launch, or Remote Activation permissions.

Memory trick: Windows applications are like tiny houses; DCOM is the lock on the door.

SMBv1 (Server Message Block version 1) is an outdated and insecure network file sharing protocol that is often disabled by default on modern operating systems.

• Superseded by SMBv2 and SMBv3.
• Known for security vulnerabilities (e.g., WannaCry).
• Disabling it can break compatibility with older clients/devices.

Memory trick: Old protocols block new connections.

A security method that encrypts all data on a hard drive or storage device, including the operating system and user files.

• Protects data at rest.
• Requires authentication at boot.
• Can be hardware or software-based.

Memory trick: Data at rest, needs a 'full' lock.

A group of independent servers (nodes) that work together to increase the availability and scalability of applications and services. Failover clustering provides high availability by automatically moving workloads to another node in case of a failure.

• Eliminates single points of failure.
• Ensures continuous service (high availability).
• Requires shared storage and heartbeat networks.

Memory trick: Cluster for Continuous Care

The number of programs and services configured to launch automatically at system startup can significantly impact boot times, even if the system performs well once fully loaded.

• Many startup items consume CPU, memory, and disk I/O.
• Can be managed via OS utilities (e.g., msconfig, systemctl).
• Does not always impact post-boot performance.

Memory trick: Long boot, but fine after? Too many programs on the startup roster.

A web server configuration that allows a single server to host multiple domain names, each with its own content and settings.

• Uses the 'Host' header in HTTP requests to differentiate sites.
• Can be IP-based or name-based.
• Commonly used in Apache and Nginx.

Memory trick: Virtual hosts are like apartments in one building, each with its own address.

A command-line utility that provides a dynamic, real-time view of a running Linux system.

• Displays process CPU and memory usage.
• Can be sorted by various metrics.
• Useful for identifying performance bottlenecks.

Memory trick: Top shows the 'top' performers (or misbehavers) on your server's stage.

High CPU utilization indicates that the processor is overworked, potentially due to legitimate workloads, inefficient software, or malicious processes.

• Identify the processes consuming CPU resources.
• Check for unexpected or unknown processes.
• Malicious software (malware, cryptominers) can cause high CPU.

Memory trick: CPU's hot, processes plot, find the culprit, make it stop!

A VM template, or golden image, is a pre-configured virtual machine that serves as a master copy for creating new VMs with identical settings, OS, and applications.

• Ensures consistency across multiple VM deployments.
• Significantly reduces deployment time and effort.
• Ideal for scaling out identical server roles (e.g., web servers, test environments).

Memory trick: Templates Create Rapid, Identical Virtual Machines.

RAID 6 stripes data with double distributed parity across all drives, tolerating two simultaneous drive failures at the cost of two drives' worth of capacity.

• Usable capacity = (n-2) x drive size
• Requires a minimum of 4 drives
• Can survive two simultaneous drive failures

Memory trick: RAID 6 always gives up two drives to double parity guards.

Dynamic Host Configuration Protocol is a network management protocol used on Internet Protocol (IP) networks for dynamically distributing network configuration parameters, such as IP addresses, for interfaces and services.

• Automates IP address assignment
• Distributes subnet mask, gateway, DNS
• Reduces manual configuration errors

Memory trick: Don't Have Confusing Protocols, Just DHCP for IPs!

A network storage protocol that allows SCSI commands to be sent over a standard TCP/IP network, providing block-level access to storage devices over Ethernet.

• Provides block-level storage access.
• Leverages existing Ethernet infrastructure, reducing costs.
• Can be implemented with standard NICs or specialized iSCSI HBAs.
• Commonly used for SANs where Fibre Channel is too expensive or complex.

Memory trick: iSCSI: 'I See SCSI' over IP.

A networking protocol that provides centralized authentication, authorization, and accounting (AAA) management for users connecting to a network service.

• Centralized AAA services.
• Widely used for network access.
• Operates over UDP.

Memory trick: RADIUS: Reach All Devices, Identify Users Securely.

Custom OS installation involves installing an operating system with specific, non-standard components like custom kernels or drivers, often necessitated by unique hardware or application requirements.

• Requires detailed knowledge of the OS and hardware.
• Often involves manual steps for driver injection or kernel compilation.
• Less common in virtualized or commodity hardware environments.

Memory trick: Manual Install Handles Unique Hardware Effectively.

Scripting languages are used to automate administrative tasks, manage systems, and interact with OS features, offering flexibility and efficiency.

• Key considerations include cross-platform support, module availability, and ease of use.
• Popular choices: Python, PowerShell, Bash.
• Different languages excel in different environments or for specific task types.

Memory trick: Python Powers Universal System Automation.

The practice of using multiple, independent power sources and paths to ensure continuous operation of a server or system in case of a power component failure.

• Requires redundant PSUs in the server
• Each PSU must have its own independent power path
• Protects against failure of a single PDU, UPS, or power feed

Memory trick: Separate paths, separate power, always stay up, never fail an hour.

NIC bonding is a technique that combines multiple network interface cards into a single logical interface to provide redundancy, load balancing, and increased throughput.

• Enhances network reliability through failover.
• Increases available bandwidth for network traffic.
• Requires compatible network switches and proper mode configuration (e.g., active-backup, LACP).

Memory trick: Bonding Links Many NICs for Resilient Data.

The practice of identifying and minimizing the number of possible points where an unauthorized user could try to enter or extract data from an environment, often by disabling unnecessary functionalities.

• Reduces avenues for exploitation.
• Involves disabling unused services and closing ports.
• A fundamental hardening technique.

Memory trick: Shrink the attack surface, fewer places to get in.

A data center cooling layout where rack fronts face cold aisles (intake) and rack backs face hot aisles (exhaust) to separate hot and cold airflow.

• Cold aisle: perforated tiles deliver cool air to equipment intakes
• Hot aisle: exhaust heat is captured and returned to cooling units
• Prevents mixing of hot and cold air, improving efficiency

Memory trick: Fronts kiss cold, backs breathe hot — never let the two meet.

The default gateway is a router that forwards traffic from a local network to other networks, including the internet. Its correct configuration is essential for external network connectivity.

• Allows devices to communicate outside their local subnet.
• Misconfiguration leads to external connectivity loss.
• Internal communication remains unaffected by gateway issues.

Memory trick: If you can talk to neighbors but not the world, check your gateway's unfurled.

In a server with redundant power supplies, the failure of one PSU means the system loses its fault tolerance for power, operating on a single point of failure until the failed unit is replaced.

• Server remains operational with one failed PSU.
• Loss of redundancy is the immediate consequence.
• Replacement is critical to restore fault tolerance.

Memory trick: Two PSUs are nice and dandy, but one goes out, redundancy's scanty.