Linux passwords class 4
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This document provides information on various topics related to file systems and passwords in Linux/Unix. It begins with discussing password standards and storing passwords. It then covers different file system types including Ext2/3/4 and ZFS, and how the file system manages file access and metadata. The rest of the document discusses features of the ZFS file system in detail. It concludes by mentioning how to change passwords using the passwd command and introduces some common Linux commands.
Linux passwords class 4
- 1. Passwords
- 2. Passwords By : Khawar Nehal 6 October 2021
- 3. Agenda Password standards Storing passwords Changing passwords File System FHS File Names Some commands
- 5. FHS FHS Presentation fhs presentation link to local drive
- 6. File Names
- 7. File Names
- 8. File System Types In computing, file system or filesystem is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one large body of data with no way to tell where one piece of data stops and the next begins.
- 9. File System Types By separating the data into pieces and giving each piece a name, the data is easily isolated and identified. Taking its name from the way paper-based data management system is named, each group of data is called a "file." The structure and logic rules used to manage the groups of data and their names is called a "file system."
- 10. File System Types There are many different kinds of file systems. Each one has different structure and logic, properties of speed, flexibility, security, size and more. Some file systems have been designed to be used for specific applications. For example, the ISO 9660 file system is designed specifically for optical discs.
- 11. File System Types File systems can be used on numerous different types of storage devices that use different kinds of media. As of 2019, hard disk drives have been key storage devices and are projected to remain so for the foreseeable future. Other kinds of media that are used include SSDs, magnetic tapes, and optical discs. In some cases, such as with tmpfs, the computer's main memory (random- access memory, RAM) is used to create a temporary file system for short-term use.
- 12. File System Types Some file systems are used on local data storage devices; others provide file access via a network protocol (for example, NFS, SMB, or 9P clients). Some file systems are "virtual", meaning that the supplied "files" (called virtual files) are computed on request (such as procfs and sysfs) or are merely a mapping into a different file system used as a backing store.
- 13. File System Types Good summary https://en.wikipedia.org/wiki/File_system Comparison https://en.wikipedia.org/wiki/Comparison_of_file_systems
- 14. Important ones to know The ones to know are ext2,3,4 and ZFS. The others are for advanced specific cases when the above ones are not capable or compatible. An example is SSD Drives and NVRAM. Not part of this intro course.
- 15. Important ones to know Ext2, ext3 and ext4 are commonly used in Linux. When you have less than 3 harddisks in a machine. ZFS can be used for making storage servers. When you have at least 3 harddisks in a machine.
- 16. Next topic The rest of the file system slides are to be skipped because they shall be too technical. Keep for reference only. Go to Slide 31
- 17. File System Types The file system manages access to both the content of files and the metadata about those files. It is responsible for arranging storage space; reliability, efficiency, and tuning with regard to the physical storage medium are important design considerations.
- 18. Linux File Systems Linux supports numerous file systems, but common choices for the system disk on a block device include the ext* family (ext2, ext3 and ext4), XFS, JFS, and btrfs. For raw flash without a flash translation layer (FTL) or Memory Technology Device (MTD), there are UBIFS, JFFS2 and YAFFS, among others. SquashFS is a common compressed read-only file system.
- 19. ZFS Examples of features specific to ZFS include: Designed for long-term storage of data, and indefinitely scaled datastore sizes with zero data loss, and high configurability.
- 20. ZFS Hierarchical checksumming of all data and metadata, ensuring that the entire storage system can be verified on use, and confirmed to be correctly stored, or remedied if corrupt. Checksums are stored with a block's parent block, rather than with the block itself. This contrasts with many file systems where checksums (if held) are stored with the data so that if the data is lost or corrupt, the checksum is also likely to be lost or incorrect.
- 21. ZFS Can store a user-specified number of copies of data or metadata, or selected types of data, to improve the ability to recover from data corruption of important files and structures.
- 22. ZFS Automatic rollback of recent changes to the file system and data, in some circumstances, in the event of an error or inconsistency.
- 23. ZFS Automated and (usually) silent self-healing of data inconsistencies and write failure when detected, for all errors where the data is capable of reconstruction. Data can be reconstructed using all of the following: error detection and correction checksums stored in each block's parent block; multiple copies of data (including checksums) held on the disk; write intentions logged on the SLOG (ZIL) for writes that should have occurred but did not occur (after a power failure); parity data from RAID/RAID-Z disks and volumes; copies of data from mirrored disks and volumes.
- 24. ZFS Native handling of standard RAID levels and additional ZFS RAID layouts ("RAID-Z"). The RAID-Z levels stripe data across only the disks required, for efficiency (many RAID systems stripe indiscriminately across all devices), and checksumming allows rebuilding of inconsistent or corrupted data to be minimized to those blocks with defects;
- 25. ZFS Native handling of tiered storage and caching devices, which is usually a volume related task. Because ZFS also understands the file system, it can use file-related knowledge to inform, integrate and optimize its tiered storage handling which a separate device cannot;
- 26. ZFS Native handling of snapshots and backup/replication which can be made efficient by integrating the volume and file handling. Relevant tools are provided at a low level and require external scripts and software for utilization.
- 27. ZFS Native data compression and deduplication, although the latter is largely handled in RAM and is memory hungry.
- 28. ZFS One major feature that distinguishes ZFS from other file systems is that it is designed with a focus on data integrity by protecting the user's data on disk against silent data corruption caused by data degradation, power surges (voltage spikes), bugs in disk firmware, phantom writes (the previous write did not make it to disk), misdirected reads/writes (the disk accesses the wrong block), DMA parity errors between the array and server memory or from the driver (since the checksum validates data inside the array), driver errors (data winds up in the wrong buffer inside the kernel), accidental overwrites (such as swapping to a live file system), etc.
- 29. ZFS A 1999 study showed that neither any of the then-major and widespread filesystems (such as UFS, Ext, XFS, JFS, or NTFS), nor hardware RAID (which has some issues with data integrity) provided sufficient protection against data corruption problems. Initial research indicates that ZFS protects data better than earlier efforts. It is also faster than UFS and can be seen as its replacement.
- 31. Changing the password passwd for the user and root
- 32. Some commands Now we shall continue with some of the hundreds of Linux and Unix commands available to administrators.
- 37. Find locate kfind Find, locate , updatedb and kfind explanation.
- 38. wildcards
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