Filesystem Managementand Backups

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Section Overview

Devices and FilesFilesystem ManagementNetwork FilesystemsBackups

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Kinds of DevicesPhysical Devices Actual hardware Examples

Hard Drives, CDROMs, Floppy Network cards and modems

Logical Devices Pseudo devices Examples

Virtual Terminals Network Ports

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Device Drivers and FilesDevice drivers Software to control hardware Compiled into the kernel Dynamically loaded moduleDevice files Located in /dev Provide application access to device Driver must also be present to use

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Making Device Filesmknod filename type major minor

filename: Name of the device fileType “c” – Character Device “b” – Block Device

Major Number: Type of device driverMinor Number: Instance (which one)/dev/MAKEDEV: Creation program

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Disk GeometryTracksTracksSectorsSectorsRead/write HeadsRead/write Heads

CylindersCylindersPartitionsPartitions

PlattersPlatters

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UNIX FilesystemsDefines how data is stored on drivesMultiple types of filesystems supportedBoot Block (1st block) Stores the bootstrap loader program

Superblock (2nd block) Copies scattered throughout the partition Stores information about the partition

Partition Size Type of File system Block Size Size & Location of inode tables Free Block list

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File systems and Partitions/ (root)

bin varusretchome

scott bobalice bin sbin local lib

man lib srcsharebin

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Why Partition?Not enough space on one diskSeparation of data Read-only areas Spool areas and free space OS upgradesBackupsPerformance

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Managing FilesystemsCreating a new filesystem Similar to DOS format mkfs – creates a filesystem (many aliases)mount – mount a partition Mount point must exist (directory) /etc/fstabumount – Unmount a partitionfsck Check/fix filesystem errors Journaling filesystems

Quotas?

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Network FilesystemsFilesystems shared via NFSClient-side: similar to local mountServer – exports shared filesystems mountd and nfsd /etc/exports and exportfs Access permissions should be selectiveshowmount -eSamba – Microsoft filesystem sharing

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Why Backups?Hardware failuresAccidental deletions or modificationSecurity incidentsUpgrades and Migrations

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Backup Plan Characteristics

Ease of use Automation of backups Selective file/directory restoresTime schedulingBackup verificationOffsite copiesPortability

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Backup MediaFloppy DisksCD-R and CD-RW DrivesRemoval Hard drives and ZipdrivesTape 4mm DAT 8mm DLT

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Backup toolsdump and restore filesystem backups Support for incremental backupstar File by file backups (archives) Easy to recover selected filesdd – Duplicate “raw” devicesmt – Control tape devicesCompression tools compress gzip

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Backup StrategiesFull Backups – Backup entire systemPartial Backups – Selective backupIncremental – Backup modified filesBasic plan Full backup on Sundays Incremental daily