Job Scheduling - Part 2

Duration: 20 min

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Module outline

Numerical Ability & Problem Solving: Speed Mathematics and Basic Mathematics, Arithmetic, Number System, HCF LCM, Divisibility Rules, Percentage, Ratio and Proportion (Ratios), Average, Profit and Loss, Simple Interest and Compound Interest, Mixture and Alligation, Time and Work, Pipe and Cistern, Speed Time and Distance, Age Problems, Partnership, Data Interpretation, Mental Ability, Sequence and Series (Series), Powers and Exponents (Surds and Indices), Algebra, Statistics, Logarithm, Mensuration and Geometry, Permutation and Combination, Probability, Sequences and Series, Powers, Surds and Logarithms, Subject-Verb Agreement, Sentence Completion, Geometry, Sentence Structure and Correction, Data Sufficiency, Trigonometry, Measurement and Quantity Take-Off, Signal Space and Optimum Detection, Probability, Statistics, Algebra, Time and Work, Speed, Time and Distance, Data Interpretation, Combinatorics
Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Seating Arrangements, Blood Relations, Directions (Direction Test), Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Analytical Reasoning (Counting Figures Reasoning), Puzzle Solving (Puzzles), Calendar, Clock, Cubes & Dices, Logical Sequence Of Words, Venn Diagram, Data Arrangement, Inequality, Analogy, Ranking, Order and Sequence, Selection Decision Table (Decision Making), Alphabet and Word Tests, Numerical Reasoning, Number System, Averages, Mixtures and Alligation, Percentages, Series Completion, Analogy and Classification, Patterns in Two-Dimensional Figures, Coding and Decoding, Mathematical Operations, Direction Sense, Logical Deduction and Induction, Syllogisms and Venn Diagrams, Critical Reasoning, Order, Ranking and Sequence, Reading Comprehension, Profit, Loss and Discount, Constraint Puzzles, Traverse Surveying, Ratio and Proportion, Mensuration, Permutations and Combinations, Clocks and Calendars, Assembling and Grouping of Shapes, Transformation of Shapes, Three-Dimensional Patterns and Visualization, Cubes and Dice, Vocabulary, Blood Relations
General Knowledge & Current Affairs (India + Rajasthan): History, Geography, Polity, Indian Economy, Static General Knowledge, State Wise GK, GK- Current Affairs, Environment, Physics
Computer Fundamentals & Operating Systems: Basics of COA, Floating Point Rep, Digital Systems & Boolean Basics, Number Representation, Number System, Introduction to OS, File Management, Windows OS, Unix OS, Linux OS, Register Transfer and Microoperations, Virtual Memory
Computer Networks: Introduction to CN, Data Communication, DLL: Error Control, DLL: Access Control, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Application Layer, Hardware Basics, Network Security
Cyber Security: Cyber Threats and Malware Attacks, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Electronic Data Interchange and E-Commerce, Physical Security and Cryptography Basics, Intrusion Detection Systems (IDS), Cyber Safety and Security, Ethical Hacking
Programming (C & OOP): C Fundamentals, Control Flow, Arrays & Pointers, Functions, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, OOPS with C++, Operators & Expressions, Sorting Algorithms, Java Fundamentals, Java
MS Office & Data Processing: MS Office Applications, Basics of DBMS
Internet & Web Technology: Society, Law & Ethics, Terms & Abbreviations, Keyboard Shortcuts, Emerging Tech Trends, Artificial Intelligence, Emerging Technologies, Internet Fundamentals, Website, Browser & Services, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security

AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture segment, titled '3.2 Job Scheduling - Part 2', systematically covers advanced job scheduling mechanisms in Linux, progressing from the syntax of Cron expressions to one-time and load-based schedulers. The session begins by detailing the four special characters used in Cron expressions: the asterisk, comma, hyphen, and slash. The instructor uses a structured table to define each symbol's meaning and provides concrete examples, such as using a hyphen for a range of values (e.g., 9-17) or a slash for step intervals (e.g., */5). Following this, the lesson transitions to one-time job scheduling using the 'at', 'atq', and 'atrm' commands. A practical terminal demonstration shows how to schedule a backup job for 10:00 PM, list the queue with 'atq', and remove a job using 'atrm'. The lecture then introduces the 'batch' command, contrasting it with 'at' by explaining that batch is load-based rather than time-based. Finally, the instructor covers 'anacron', a scheduler designed for systems that are not running continuously. This includes an explanation of the 'anacrontab' configuration file and its basic format (period, delay, job-identifier, command). The segment concludes with a comparative table summarizing the basic differences between Cron, at, batch, and anacron.

Chapters

0:00 – 2:00 00:00-02:00
The lecture introduces the 'Cron Special Characters' slide, which explains how symbols define and control schedules. A table is presented listing the Asterisk (every value), Comma (multiple values), Hyphen (range of values), and Slash (step/interval). The instructor highlights each row sequentially, underlining examples such as '0 9-17 * * *' for a range and '*/5 * * * *' for an interval.
2:00 – 5:00 02:00-05:00
The lesson transitions to one-time job scheduling in Linux using the 'at', 'atq', and 'atrm' commands. A terminal demonstration shows a user scheduling a job with the command 'at 10:00 PM' followed by an echo statement. The instructor explains that the job is submitted using Ctrl+D (or <EOT>), and demonstrates how to view the queue with 'atq' and delete a specific job using 'atrm 7'.
5:00 – 10:00 05:00-10:00
The instructor continues the breakdown of the 'at' command, using red hand-drawn circles and arrows to emphasize the syntax components: the time, the command to execute, and the submission signal. The segment then introduces the 'batch' command, defining it as a tool to schedule jobs when system load is low. A two-column table contrasts 'at' (time-based) with 'batch' (load-based), noting that both are used for one-time jobs.
10:00 – 15:00 10:00-15:00
The focus shifts to 'anacron', described as a job scheduler for periodic jobs on systems that may not be running continuously. An example is provided where a daily backup job is executed only after the system starts if it was missed. Key features listed include its use for periodic jobs, day-based intervals, and the ability to catch up on missed executions when the system becomes available.
15:00 – 19:46 15:00-19:46
The lecture details the 'anacrontab' configuration file located at '/etc/anacrontab'. The basic format is explained as period, delay, job-identifier, and command, illustrated by the example '1 5 daily-backup /home/user/backup.sh'. The segment concludes with a summary slide titled 'Cron vs at vs batch vs anacron', featuring a table that compares the four tools across their main purpose, scheduling basis, repetition capabilities, and best-suited use cases.

The lecture follows a logical progression from recurring to one-time and finally to conditional scheduling. It starts by reinforcing the syntax of Cron expressions, ensuring students understand how to manipulate time fields using special characters. It then moves to the 'at' family of commands, providing a clear workflow for creating, monitoring, and deleting one-time tasks. The introduction of 'batch' serves as a direct contrast to 'at', highlighting the difference between time-based and load-based triggers. Finally, 'anacron' is presented as a solution for the common problem of missed schedules on non-continuous systems. The final comparative table serves as a consolidation tool, helping students distinguish which scheduler is appropriate for specific administrative tasks based on their frequency and system availability.