chap03 managing the solaris oe file system

7/30/2019 Chap03 Managing the Solaris OE File System

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1AITA\SWBU\SOLARIS\08

Managing the Solaris OE File System


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Solaris OE File Systems

Disk-based file systems

Distributed file systems

Pseudo file systems


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Disk-based file systems

ufs

The UNIX file system in the Solaris OE is based

on the Berkeley fast file system.

hsfs The High Sierra file system is a special-purpose

file system developed for use on CD-ROM media.


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pcfs

The PC file system is a UNIX implementation of the DOS

FAT file system. The pcfs allows the Solaris OE to access

PC-DOS formatted file systems.

udfs The Universal Disk Format file system is used for optical

storage targeted at DVD and CD-ROM media.


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Distributed File Systems

NFS

The network file system allows users to share files among

many types of systems on the network.


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Psuedo File Systems

tmps

The temporary file system stores files in memory,

which avoids the overhead of writing to a disk-based

file system. The tmpfs file system is created and

destroyed every time the system is rebooted.

swapfs

The swap file system is used by the kernel tomanage swap space on disks.


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fdfs The file descriptor file system provides explicit names for

opening file by using file descriptors (eg:- /dev/fd/0, /dev/fd/1)in the /dev/fd directory.


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procfs

The process file system contains a list of active processes in the

/proc directory. The processes are listed by process number.

mntfs

The mount file system provides read-only information from the

kernel about locally mounted file systems.


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Viewing the Solaris OE ufs File System

Disk Label (VTOC)

The VTOC contains the partition table for the disk.

The VTOC resides in the first disk sectr (512 bytes blocks).

Only the first disk slice contains a VTOC.


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Boot Block The bootstrap program (bootblk) resides in the 15 disk

sectors that follow the VTOC. Only the / (root) file system

has an active boot block


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Primary Superblock

The superblock resides in the next 16 sectors that follow that boot

block. The superblock contains the following information:

The number of data blocks The number of cylinder groups

The size of a data block and fragment

A description of the hardware, derived from the label The name of the mount point

File system state flag: clean, stable, active, logging or unknown


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Backup Superblocks When the file system is created, each cylinder group

replicates the superblock beginning at Sector 32.

The replication protects the critical data in the superblockagainst catastrophic loss.


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Cylinder Groups

Each file system is divided into cylinder groups with aminimum default size of 16 cylinders per group.

Cylinder groups improve disk access


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Cylinder Group Blocks

Cylinder group block is a table in each cylinder group that describes

the cylinder group: The number of inodes

The number of data blocks in the cylinder group

The number of directories Free blocks, free inodes, and free fragments in the cylinder

group

The free block map

The used inode map


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The ufs inode

An inode contains the following information about a file:

The type of file and the access modes The UID & GID of the files owner and group

The size of the file

The link count

The time the flag was last accessed and modified and the

inode changes

The total number of data blocks used by or allocated to the

file

Two types of pointers: direct pointers and indirect pointers


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Solaris ufs File System Structure

Disk label

bootblk

Primary superblock

First Cylinder Group

Backup superblock

Cylinder Group Block

Inode TableData blocks

Second Cylinder Group

Backup superblock

Cylinder Group BlockInode Table

Data blocks


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Direct Pointers

Inside the inode there are 12 direct pointers, which

contain addresses for the files first 12 data blocks. The 12 direct pointers can each reference 8-Kbyte data

blocks for a file that is upto 96Kbytes


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Indirect Pointers

Single indirect pointer

Refers to a file system block that contains pointers to datablocks.

This file system block contains 2048 additional addresses of

8=Kbyte data blocks, which can point to an additional 16

Mbytes of data


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Double indirect pointer

Refers to file system block that contains single indirectpointers.

Each indirect pointer refers to a file system block that

contains the data block pointer.

Double indirect pointers point to an additional 32Gbytes of

data


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Triple indirect pointer Can reference up to an additional 64 Tbytes of data.

However, the maximum size of a ufs file system is limited to 1

Tbyte due to the maximum address space of 32-bits for thedevice drivers


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Data Blocks

The remaining space allocated to the ufs file system holds data

blocks. Data blocks are allocated, by default, in 8-Kbyte logical block

sizes.

The blocks are further divided into 1-Kbyte fragments.


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Creating a New ufs File System

Using the newfs command As a root user to create a new ufs file system:

# newfs /dev/rdsk/c1t0d0s0

The newfs command asks for confirmation beforecontinuing


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minfree value To display the minfree value for the filesystem:

#fstyp -v /dev/rdsk/c0t0d0s0

To change the minfree value:

#tunefs -m 1 /dev/rdsk/c1t0d0s0

Changes the minfree value from the default 10% to 1%


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Checking the File System by using the fsck

command

Data Inconsistencies checked by the fsck command

Superblock Consistency

Cylinder Group Block Consistency

Inode Consistency Data Block Consistency

The lost+found directory - fsck puts the files and directoriesthat are allocated but unreferenced in this directory


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Noninteractive Mode

During a normal system boot, fsck command operates innoninteractive mode, which is often referred to as preen, orsilent mode.

Addresses only minor inconsistencies.

Interactive Mode

Lists each problem it encounters, followed by a suggestedcorrective action in the form of a question that requires a yesor no response.


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fsck usage

#fsck /dev/rdsk/c0t0d0s7 #fsck /export/home

#fsck -o f,p /dev/rdsk/c0t0d0s5 - checks and repairs the file

system with the force (f) and preen (p) options


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Using Backup Superblocks

To display the alternative superblocks: #newfs -N /dev/rdsk/c0t0d0s7

To use a backup superblock:

#fsck -o b=32 /dev/rdsk/c0t0d0s7


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Monitoring File System Use

df - Displays the number of free disk blocks df -options mount_point

du - Summarizes disk use

du -options directory quot - Summarizes file system ownership

quot -options filesystem

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