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A Systematic Approach to Server Troubleshooting Diagnosing methodically.WHAT TO ESTABLISH FIRSTWhat exactly is broken, in observable... Archives and Compression Bundling and shrinking files.WHAT tar DOESBundles many files into one, optionally compressed.WHY... Automating Administration Safely Making routine work repeatable.WHAT TO AUTOMATEBackups Log rotation Certificate renewal Updates,... Automating Server Health Checks A script that tells you what is wrong.WHAT TO CHECKDisk space on every mount Inode usage Load... Background Jobs and Long Tasks Running things that outlast your session.WHAT HAPPENS WHEN YOU DISCONNECTProcesses started in... Backups From the Command Line Protecting what is on the server.WHAT TO BACK UPWebsite files Databases Mail Configuration... Building Good Server Habits Practices that prevent incidents.WHAT TO DO BEFORE EVERY DESTRUCTIVE COMMANDRead the path aloud,... Building a Personal Toolkit What to carry between servers.WHAT TO ASSEMBLEA small set of scripts you use repeatedly Your... Changing Permissions and Ownership chmod and chown.WHAT chmod DOESChanges permissions.WHAT THE TWO FORMS ARENumeric, setting... Checking What Is Listening on a Port Finding which process owns a port.WHY THIS COMES UP CONSTANTLYA service will not start because... Choosing Between Managed and Unmanaged Servers What you take on.WHAT UNMANAGED MEANSYou receive a machine and an address, and everything else is... Command History and Efficiency Working faster.WHAT HISTORY PROVIDESA record of commands you have run.HOW TO SEARCH ITControl and... Command Line Confidence Getting comfortable.WHAT PUTS PEOPLE OFFNo visual feedback Unforgiving mistakes Terse error... Command Line Tools Worth Knowing Beyond the essentials.WHAT xargs DOESBuilds command lines from input.WHERE IT HELPSActing on the... Command Line for cPanel Account Owners Shell access without root.WHAT SHELL ACCESS PROVIDES ON SHARED HOSTINGFaster file operations than... Common Beginner Mistakes on Servers What goes wrong repeatedly.RUNNING EVERYTHING AS ROOTNo safety net, and no record of who did... Comparing Files and Directories Finding what differs.WHAT diff DOESShows the differences between two files.WHAT THE USEFUL FORM... Configuration Management Basics Managing many servers.WHAT THE PROBLEM ISServers configured by hand diverge, and nobody knows... Connecting to a Server With SSH Getting a shell remotely.WHAT SSH ISAn encrypted connection to a shell on another machine.WHAT... Creating and Managing Swap Space Adding overflow memory.WHEN TO ADD ITWhen a machine has little memory and occasional spikes.WHEN... Creating, Copying and Moving Files Basic manipulation.WHAT touch DOESCreates an empty file, or updates a file's timestamp.WHAT mkdir... Decommissioning a Server Shutting one down properly.WHAT TO ESTABLISH FIRSTWhat is actually on it.HOWCheck for sites,... Detecting a Compromised Server Recognising intrusion.WHAT SUGGESTS COMPROMISEUnexplained processes Unexpected listening ports... Diagnosing High Server Load Working out what is consuming the machine.WHAT TO ESTABLISH FIRSTWhether load is processor,... Diagnosing Network Problems on a Server Working through connectivity faults.WHAT TO ESTABLISH FIRSTWhether the problem is local, on the... Diagnosing Slow Databases Finding the query at fault.WHAT TO LOOK AT FIRSTThe process list, for queries currently... Disk Space and Storage Finding and freeing space.WHAT df DOESShows space per mounted file system.WHAT THE HUMAN-READABLE... Documenting Server Configuration Recording what exists.WHY IT MATTERSServers outlive memory, and the person who set it up is not... Editing Files on the Server nano and vi.WHAT nano ISA simple editor, with commands shown at the bottom of the screen.WHY IT... Environment Variables and the Shell Environment How the shell knows things.WHAT AN ENVIRONMENT VARIABLE ISA value available to programs the shell... Firewalls and Access Control Controlling what reaches your server.THE PRINCIPLEDeny by default. Allow only what is needed.WHAT... Getting Help on the Server Finding documentation.WHAT man DOESShows the manual for a command.HOW TO NAVIGATE ITAs with less:... Handling Very Large Files When size breaks the usual tools.WHAT BREAKSOpening a file in an editor that loads it entirely... Installing and Managing Software Package management.WHAT A PACKAGE MANAGER DOESInstalls software with its dependencies, from... Keeping Skills Current Staying capable as systems change.WHAT CHANGESInit systems, network tooling and package managers... Kernel and System Updates Keeping the base current.WHY IT MATTERSKernel vulnerabilities permit privilege escalation,... Learning Linux Administration Developing the skill.WHAT TO PRACTISE ONA machine you can destroy.WHAT THAT MEANS PRACTICALLYA... Linux Command Line and Server Administration: Everything That Matters, Briefly The whole category in one page.CHECK WHICH MACHINE YOU ARE ON BEFORE ANY DESTRUCTIVE COMMANDIt is... Linux Distributions and Their Differences Why instructions vary.WHAT A DISTRIBUTION ISA packaged collection of the kernel, tools and a... Managing Cron for Multiple Users Scheduled tasks across accounts.WHERE CRONTABS LIVEOne per user, stored by the system rather than... Managing Databases From the Shell MySQL and MariaDB on the command line.HOW TO CONNECTThe client command, with a user, a password... Managing Log Rotation Stopping logs filling the disk.WHAT ROTATION DOESRenames the current log, starts a new one,... Managing Mail Services From the Shell Exim, queues and delivery.WHAT THE QUEUE ISMessages accepted but not yet delivered.HOW TO SEE ITS... Managing Multiple PHP Versions Running different versions per site.WHY IT ARISESOlder applications require older versions, while... Managing Processes Seeing and controlling what runs.WHAT A PROCESS ISA running program, with an identifier.WHAT ps... Managing Server Access for a Team Several people, one machine.WHAT TO AVOIDA shared account and a shared password.WHYNothing can be... Managing Server Storage Growth Planning for data that accumulates.WHAT GROWS PREDICTABLYDatabases Uploaded files Logs Backups... Managing Services With systemd Starting and stopping what runs.WHAT systemd ISThe system that starts services and manages... Migrating a Server Moving everything to a new machine.WHAT TO PLAN FIRSTAn inventory of what is on the old... Monitoring Server Performance Understanding what the machine is doing.WHAT TO MEASUREProcessor use Memory use Disk activity and... Monitoring and Alerting Basics Knowing before your customers do.WHAT TO MONITOR ON ANY SERVERWhether it responds Disk space Load... Mounting and Managing File Systems Attaching storage.WHAT MOUNTING ISAttaching a file system to a directory in the tree.WHAT A MOUNT... Moving Around the File System Finding your way.WHAT THE STRUCTURE ISA single tree starting at the root, written as a forward... Networking From the Command Line Checking connectivity.WHAT ip DOESShows and configures addresses, routes and interfaces.WHAT... Practical Command Line Recipes Commands worth knowing by shape.FINDING THE LARGEST DIRECTORIESSummarise usage one level deep,... Processing Text sort, cut, awk and sed.WHAT sort DOESOrders lines.WHAT THE USEFUL OPTIONS ARENumeric ordering... Quoting in the Shell Getting text through unchanged.WHY QUOTING EXISTSTo stop the shell interpreting characters you... Rate Limiting and Abuse Control Protecting a server from traffic.WHAT TO ESTABLISH FIRSTWhether the traffic is malicious,... Reading Configuration Files Understanding what you are editing.WHAT MOST CONFIGURATION SHARESComments, usually beginning with... Reading Files From the Shell Looking at contents.WHAT cat DOESPrints a whole file.WHEN TO USE ITShort files only.WHY NOT LONG... Reading System Logs Where the answers are.WHERE LOGS LIVEUnder var and log, traditionally as text files.WHAT THE... Recovering a Server You Cannot Access When SSH will not connect.WHAT TO ESTABLISH FIRSTWhether the machine is running at all.HOWWhether... Redirection and Pipes Connecting commands together.WHAT THE THREE STREAMS AREStandard input Standard output Standard... Reducing Downtime During Maintenance Working on live systems.WHAT TO ESTABLISHWhat will be affected, and for how long.WHAT TO... Responding to a Server Compromise What to do afterwards.WHAT THE ORDER ISContain Preserve Establish scope Remediate Verify... Restoring From Backups Putting things back.WHAT TO ESTABLISH FIRSTWhat exactly is broken, and from when.WHYRestoring... Root, sudo and Privilege Doing things that require authority.WHAT ROOT ISThe account with no restrictions.WHY DIRECT ROOT... SSL Certificates From the Command Line Issuing and checking.WHAT TO CHECK ON A LIVE SITEThe certificate presented, its dates, and the... Scheduling Tasks With Cron Running things automatically.WHAT cron ISA service that runs commands on a schedule.WHAT A... Searching Inside Files grep and its relatives.WHAT grep DOESPrints lines matching a pattern.WHAT THE USEFUL OPTIONS... Searching for Files find and locate.WHAT find DOESWalks a directory tree and matches files by criteria.WHAT THE BASIC... Securing a Linux Server Basic hardening.WHAT TO DO FIRSTKeep the system updated.WHY FIRSTMost compromises exploit known... Server Administration in the Nigerian Context Local realities.WHAT CONSTRAINS WORK HEREConnectivity that drops mid-session Power affecting... Setting Up a New Server The first hour.WHAT TO DO FIRSTUpdate everything.WHAT NEXTCreate a named account for yourself Add... Shell Scripting Basics Automating with scripts.WHAT A SCRIPT ISA file of commands, run in sequence.WHAT THE FIRST LINE... Signals and How Processes Respond Beyond kill.WHAT A SIGNAL ISA notification sent to a process.WHAT THE COMMON ONES ARETerminate,... Swap and Memory Management When memory runs short.WHAT SWAP ISDisk space used as an overflow for memory.WHY IT IS SLOWDisk... Time, Time Zones and Synchronisation Keeping clocks correct.WHY IT MATTERSLogs from different machines cannot be correlated if clocks... Transferring Files Between Machines scp, rsync and sftp.WHAT scp DOESCopies over an SSH connection.WHAT ITS WEAKNESS ISIt restarts... Understanding Exit Codes and Error Messages Reading what commands tell you.WHAT AN EXIT CODE ISA number a command returns on finishing.WHAT... Understanding File Descriptors and Open Files Why deleted files still use space.WHAT A FILE DESCRIPTOR ISA process's handle to an open file.WHY... Understanding File Permissions Who can do what.THE THREE PERMISSIONSRead, write, execute.THE THREE GROUPSThe owner, the group,... Understanding Load Average Interpreting the three numbers.WHAT IT MEASURESThe average number of processes running or... Understanding Memory Usage Reports Reading free and top correctly.WHAT CONFUSES EVERYONEA server reporting almost no free memory... Understanding Symbolic and Hard Links Files in more than one place.WHAT A SYMBOLIC LINK ISA file pointing at another path.WHAT A HARD... Understanding Web Server Logs Reading access and error logs.WHAT AN ACCESS LOG RECORDSEvery request: source, time, what was... Understanding What Actually Breaks Servers The common causes, ranked.WHAT CAUSES MOST INCIDENTSA full disk A configuration change An expired... Understanding the Boot Process What happens before you can log in.WHY IT MATTERSWhen a machine does not come back, knowing the... Users and Groups Accounts on the system.WHAT A USER HASA name A numeric identifier A home directory A shell Group... Using Version Control on Servers Tracking changes to configuration.WHY IT APPLIES TO SERVERSConfiguration changes, and knowing... Web Server Basics From the Shell Apache, nginx and LiteSpeed.WHAT TO ESTABLISH FIRSTWhich web server is actually running.HOWList... What the Command Line Actually Is The shell, and why it exists.WHAT IT ISA program that reads what you type, runs it, and shows the... When to Ask for Help Recognising the limit.WHEN TO STOP AND ASKWhen the next step could lose data When you do not... Wildcards and Shell Expansion What the shell does before running a command.WHAT EXPANSION MEANSThe shell rewrites your command... Working Safely on Production Servers Rules for live systems.WHAT TO ESTABLISH BEFORE TOUCHING ANYTHINGWhich machine, and what depends... Working With Text File Formats Line endings and encodings.WHAT THE LINE ENDING PROBLEM ISWindows uses two characters to end a... Working With Two Servers at Once Migrations and parallel work.WHERE THIS ARISESMigrating between servers Comparing a working... Working With cPanel Servers From the Shell Command line on a managed server.WHAT TO UNDERSTAND FIRSTThe panel manages configuration, and... Writing Safe and Useful Scripts Scripts that do not cause incidents.WHAT TO DO BEFORE ANY DESTRUCTIVE ACTIONCheck that the... systemd Timers The modern alternative to cron.WHAT THEY AREScheduled units managed by systemd.WHAT THEY PROVIDE...
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