Linux Metadata
Linux Metadata Where is Metadata Stored? struct stat { Metadata in the File dev_t st_dev; /* device */ Metadata in the Directory ino_t st_ino; /* inode */ Crash Recovery mode_t st_mode; /* protection */ The Unix Filesystem nlink_t st_nlink; /* number of hard links File Operations uid_t st_uid; /* user ID of owner */ File System Layout The Windows FAT gid_t st_gid; /* group ID of owner */ File System dev_t st_rdev; /* device type (if inode Dump/Restore off_t st_size; /* total size, in bytes blksize_t st_blksize; /* blocksize for filesystem blkcnt_t st_blocks; /* number of blocks allocated time_t st_atime; /* time of last access time_t st_mtime; /* time of last modification time_t st_ctime; /* time of last status };
1 / 42 Where is Metadata Stored?
Linux Metadata ■ Where is Metadata In the file? Stored? Metadata in the File ■ In the directory entry? Metadata in the Directory ■ Elsewhere? Crash Recovery ■ The Unix Filesystem Split?
File Operations
File System Layout The Windows FAT File System
Dump/Restore
2 / 42 Metadata in the File
Linux Metadata Where is Metadata ■ (Sort of) done by Apple: resource and data Stored? Metadata in the File forks Metadata in the Directory ■ Not very portable — when you copy the file Crash Recovery
The Unix Filesystem to/from other systems, what happens to the File Operations metadata? File System Layout ■ No standardized metadata exchange format The Windows FAT File System
Dump/Restore
3 / 42 Metadata in the Directory
Linux Metadata ■ Where is Metadata Speeds access to metadata Stored? Metadata in the File ■ Makes hard links difficult — need to keep Metadata in the Directory copies of the metadata synchronized Crash Recovery ■ The Unix Filesystem Makes directories larger; often, one doesn’t File Operations need the metadata File System Layout ■ Many newer systems keep at least a few bits of The Windows FAT File System metadata in the directory, notably file type — Dump/Restore knowing if something is or isn’t a directory speeds up tree walks considerably
4 / 42 Crash Recovery
Linux Metadata ■ Where is Metadata Must ensure that file systems are in a Stored? Metadata in the File consistent state after a system crash Metadata in the Directory ■ Example: don’t write out directory entry Crash Recovery Crash Recovery before the metadata Repairing Damage Log-Structured File ■ Example: File systems are generally trees, not Systems Modern Disks graphs; make sure things always point The Unix Filesystem somewhere sane File Operations ■ File System Layout What if the file has blocks but the freelist The Windows FAT File System hasn’t been updated? Dump/Restore ■ Principle: order writes to ensure that the disk is always in a safe state
5 / 42 Repairing Damage
Linux Metadata ■ Where is Metadata At boot-time, run a consistency checker except Stored? Metadata in the File after a clean shutdown Metadata in the Directory ■ Example: fsck (Unix) and scandisk Crash Recovery Crash Recovery (Windows) Repairing Damage Log-Structured File ■ Force things to a safe state; move any Systems Modern Disks allocated but unreferenced blocks and files to a The Unix Filesystem recovery area File Operations
File System Layout The Windows FAT File System
Dump/Restore
6 / 42 Log-Structured File Systems
Linux Metadata ■ Where is Metadata Instead of overwriting data, append the Stored? Metadata in the File changes to a journaling area Metadata in the Directory ■ The file system is thus always consistent, as Crash Recovery Crash Recovery long as writes are properly ordered. Repairing Damage Log-Structured File ■ Hmm — is that a reasonable assumption? Systems Modern Disks
The Unix Filesystem
File Operations
File System Layout The Windows FAT File System
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7 / 42 Modern Disks
Linux Metadata ■ Where is Metadata Modern disks do a lot of buffering Stored? Metadata in the File ■ Cache size on new Seagate drives: 2-16M bytes Metadata in the Directory ■ The drive will reorder writes to optimize seek Crash Recovery Crash Recovery times Repairing Damage Log-Structured File ■ If a bad block has been relocated, you can’t Systems Modern Disks even predict when seeks will occur; only the The Unix Filesystem drive knows File Operations ■ File System Layout What if the power fails when data is buffered? The Windows FAT File System
Dump/Restore
8 / 42 Linux Metadata Where is Metadata Stored? Metadata in the File Metadata in the Directory
Crash Recovery
The Unix Filesystem The Unix Filesystem From the Process Directories The Unix Filesystem Finding a File . and .. I-Nodes What’s in an I-Node? Disk Blocks in the I-Node Multiple Layers of Indirection
File Operations
File System Layout The Windows FAT File System
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9 / 42 The Unix Filesystem
Linux Metadata ■ Where is Metadata Let’s take a high-level look at the Unix file Stored? Metadata in the File system Metadata in the Directory ■ Though details differ (a lot) for, say, Windows, Crash Recovery
The Unix Filesystem at a high level things are pretty similar The Unix Filesystem ■ From the Process We’ll discuss the actual code paths next time Directories ■ Finding a File Note: all modern operating systems support . and .. I-Nodes multiple file system types; differences hidden What’s in an I-Node? by abstraction layer. Disk Blocks in the I-Node Multiple Layers of Indirection
File Operations
File System Layout The Windows FAT File System
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10 / 42 From the Process
Linux Metadata ■ Where is Metadata The process has two crucial directory Stored? Metadata in the File attributes, the current root and the current Metadata in the Directory working directory Crash Recovery ■ The Unix Filesystem Paths that start with a / (known as absolute The Unix Filesystem From the Process paths) start from the current root; those that Directories Finding a File do not start with a / (relative paths) start . and .. I-Nodes from the current working directory What’s in an ■ I-Node? (Roots other than the real root are a security Disk Blocks in the I-Node Multiple Layers of mechanism; we’ll discuss that later in the Indirection semester.) File Operations
File System Layout The Windows FAT File System
Dump/Restore
11 / 42 Directories
Linux Metadata ■ Where is Metadata On some Unix systems, directories can be read Stored? Metadata in the File like any other file with read(); on Linux, you Metadata in the Directory must (and on other Unix systems you should) Crash Recovery
The Unix Filesystem use readdir() The Unix Filesystem ■ From the Process A directory entry consists of a variable-length Directories Finding a File name and an i-node number . and .. ■ I-Nodes (What’s an i-node?) What’s in an ■ I-Node? By convention, on most Unix systems the first Disk Blocks in the I-Node . .. Multiple Layers of two entries in a directory are and — the Indirection current and parent directories File Operations ■ File System Layout Don’t count on them being there; they’re not The Windows FAT File System guaranteed by the spec!
Dump/Restore
12 / 42 Finding a File
Linux Metadata ■ Where is Metadata Find the next component in the pathname Stored? Metadata in the File ■ Read the current directory looking for it Metadata in the Directory ■ If there’s another component to the path name Crash Recovery
The Unix Filesystem and this element is a directory, repeat, starting The Unix Filesystem From the Process from this element Directories ■ Finding a File When we’re done, the result is an i-node . and .. I-Nodes number What’s in an I-Node? Disk Blocks in the I-Node Multiple Layers of Indirection
File Operations
File System Layout The Windows FAT File System
Dump/Restore
13 / 42 . and ..
Linux Metadata ■ Where is Metadata Note how . and .. work Stored? Metadata in the File ■ . has the i-node number of the current Metadata in the Directory directory — you start again from this node for Crash Recovery
The Unix Filesystem the next component The Unix Filesystem ■ From the Process It’s just another directory; to (this part of) the Directories Finding a File kernel, there’s nothing special about it . and .. ■ I-Nodes The same is true for .. — it “happens” to What’s in an I-Node? point up a level in the directory tree. Disk Blocks in the I-Node ■ Multiple Layers of Following a search path does not rely on the Indirection directory structure being a tree! That’s File Operations
File System Layout primarily needed for orderly tree walks. The Windows FAT ■ File System (Mental exercise: symbolic links do introduce Dump/Restore the possiblity of loops. How can this be dealt with?) 14 / 42 I-Nodes
Linux Metadata ■ Where is Metadata What’s an i-node? Stored? Metadata in the File ■ An i-node holds most of the metadata for a Metadata in the Directory Unix file — on classic Unix, it holds all but the Crash Recovery
The Unix Filesystem i-node number itself The Unix Filesystem ■ From the Process The i-list is a disk-resident array i-nodes Directories ■ Finding a File The i-node number is just an index into this . and .. I-Nodes array What’s in an ■ I-Node? Looked at another way, a directory entry maps Disk Blocks in the I-Node Multiple Layers of a name to an array entry Indirection ■ Files are actually described by i-nodes, not by File Operations
File System Layout names The Windows FAT File System
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15 / 42 What’s in an I-Node?
Linux Metadata ■ Where is Metadata All of the fields from the stat structure Stored? Metadata in the File ■ A few other pieces of user-settable metadata Metadata in the Directory (flags) Crash Recovery ■ The Unix Filesystem Disk block information — where on disk the The Unix Filesystem From the Process file resides? Directories ■ Finding a File How many blocks is enough? . and .. ■ I-Nodes Put another way, how big can a file be? What’s in an I-Node? Disk Blocks in the I-Node Multiple Layers of Indirection
File Operations
File System Layout The Windows FAT File System
Dump/Restore
16 / 42 Disk Blocks in the I-Node
Linux Metadata ■ Where is Metadata If we have a small array, we limit the size of a Stored? Metadata in the File file too much Metadata in the Directory ■ If we have a large array, we waste space in the Crash Recovery
The Unix Filesystem i-list, because most files aren’t huge The Unix Filesystem ■ From the Process We have a modest-size array of block Directories Finding a File addresses, followed by the address of an . and .. indirect block I-Nodes What’s in an ■ I-Node? The indirect block is an array of disk addresses Disk Blocks in the I-Node ■ Multiple Layers of Hmm — suppose the i-node points to ten 4K Indirection blocks, followed by an indirect block. The File Operations
File System Layout maximum size of a file is then The Windows FAT File System 4096 × 10 + (4096/4) × 4096 Dump/Restore ■ That’s 4,235,264 bytes – not nearly big enough
17 / 42 Multiple Layers of Indirection
Linux Metadata ■ Where is Metadata “Any problem in software can be solved by Stored? Metadata in the File adding another layer of indirection” —David Metadata in the Directory Wheeler Crash Recovery ■ The Unix Filesystem The second indirect block is a double indirect The Unix Filesystem From the Process block Directories ■ Finding a File That gives us 4096 × 10 + (4096/4) × 4096 + . and .. I-Nodes ((4096/4) × 4096/4) × 4096 bytes — about 4G What’s in an ■ I-Node? Is that enough? Some systems today have Disk Blocks in the I-Node Multiple Layers of triple indirect blocks. . . Indirection ■ Metanote: PDP-11 Unix had triple indirect File Operations
File System Layout blocks; when file system blocks became 4K The Windows FAT File System (more or less), there was no need for them. Dump/Restore But disks and files grew bigger. . .
18 / 42 Opening a File
Linux Metadata ■ Where is Metadata When a file is opened, the i-node is read into Stored? Metadata in the File memory (if necessary) and its reference count Metadata in the Directory is incremented Crash Recovery ■ The Unix Filesystem A file table entry is created for it File Operations ■ The index in the file table is passed back to Opening a File Creating a File the application as the file descriptor Reading a File Writing a File ■ Virtually all operating systems have this notion Seek Closing a File — a file handle — that is a short way of Linking to a File Unlinking a File referring to an open file. Updating Metadata Creating Directories ■ More complex for special files — wait a few Deleting Directories Renaming days I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 19 / 42 Creating a File
Linux Metadata ■ Where is Metadata See if there’s a directory entry. Stored? Metadata in the File ■ If there is, it’s like opening a file (but you may Metadata in the Directory have to truncate it) Crash Recovery ■ The Unix Filesystem If there’s no entry, create one. File Operations ■ That involves writing to the directory, which is Opening a File Creating a File a lot like writing to a regular file Reading a File Writing a File ■ It also involves finding and allocating a free Seek Closing a File i-node Linking to a File Unlinking a File ■ Directory entries are free if the i-node number Updating Metadata Creating Directories is 0; i-nodes are free if the link count is 0 Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 20 / 42 Reading a File
Linux Metadata ■ Where is Metadata Convert the current byte offset to a block Stored? Metadata in the File number Metadata in the Directory ■ Read that block from the disk Crash Recovery ■ The Unix Filesystem Pass the proper bytes back to the user File Operations ■ Update the current byte offset Opening a File Creating a File ■ Optional: if access to the file appears to be Reading a File Writing a File sequential, start — but don’t wait for — the Seek Closing a File read of the next block Linking to a File Unlinking a File ■ Get it in the buffer cache ahead of use, to Updating Metadata Creating Directories improve performance Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 21 / 42 Writing a File
Linux Metadata ■ Where is Metadata Are we writing to the middle of a block? Stored? Metadata in the File ■ If so, read that block in Metadata in the Directory ■ If not, allocate a new block from the freelist Crash Recovery
The Unix Filesystem and add it to the i-node File Operations ■ Copy the data from the user to a buffer Opening a File Creating a File ■ Mark that buffer dirty, so that it will Reading a File Writing a File (eventually) be written out Seek Closing a File ■ Update the file offset pointer Linking to a File Unlinking a File Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 22 / 42 Seek
Linux Metadata ■ Where is Metadata Simply change the current byte offset Stored? Metadata in the File ■ Does not actually move the disk arm Metadata in the Directory ■ Doing that is probably pointless on a Crash Recovery
The Unix Filesystem multitasking system
File Operations Opening a File Creating a File Reading a File Writing a File Seek Closing a File Linking to a File Unlinking a File Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 23 / 42 Closing a File
Linux Metadata ■ Where is Metadata Decrement the i-node’s reference count Stored? Metadata in the File ■ Delete the file table entry Metadata in the Directory ■ If the i-node’s link count is 0, the file has been Crash Recovery
The Unix Filesystem deleted; see below File Operations ■ Everything else is automatic Opening a File Creating a File Reading a File Writing a File Seek Closing a File Linking to a File Unlinking a File Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 24 / 42 Linking to a File
Linux Metadata ■ Where is Metadata Create a new directory entry Stored? Metadata in the File ■ But — the i-node number is the number of the Metadata in the Directory existing file Crash Recovery ■ The Unix Filesystem Increment the i-node’s link count
File Operations Opening a File Creating a File Reading a File Writing a File Seek Closing a File Linking to a File Unlinking a File Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 25 / 42 Unlinking a File
Linux Metadata ■ Where is Metadata Decrement the link-count Stored? Metadata in the File ■ If the link-count is still non-zero, the file has Metadata in the Directory other names; do nothing more Crash Recovery ■ The Unix Filesystem If the link-count is now 0 (and the in-memory File Operations reference count is 0), the file is being deleted Opening a File Creating a File ■ Return all of its blocks to the free list Reading a File Writing a File ■ (Note: you can unlink an open file; it isn’t Seek Closing a File actually deleted until it’s closed. Query: what Linking to a File Unlinking a File happens if the system crashes with a file in Updating Metadata Creating Directories that state?) Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 26 / 42 Updating Metadata
Linux Metadata ■ Where is Metadata When a file is read, the access time needs to Stored? Metadata in the File be updated Metadata in the Directory ■ When a file is written, the modified time needs Crash Recovery
The Unix Filesystem to be updated File Operations ■ If the user changes things like file permissions, Opening a File Creating a File make the appropriate changes Reading a File Writing a File ■ Mark the in-memory i-node as dirty Seek Closing a File ■ Also update the i-node change time Linking to a File Unlinking a File ■ Periodically, dirty i-nodes are rewritten to disk Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 27 / 42 Creating Directories
Linux Metadata ■ Where is Metadata Similar to creating a file Stored? Metadata in the File ■ But — the kernel first writes the . and .. Metadata in the Directory entries Crash Recovery ■ The Unix Filesystem Increment the link count in the parent File Operations directory — .. points to it Opening a File Creating a File ■ (All writes to directories are done by Reading a File Writing a File specialized system calls; user programs cannot Seek Closing a File write directories directly via write() on any Linking to a File Unlinking a File modern Unix) Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 28 / 42 Deleting Directories
Linux Metadata ■ Where is Metadata First make sure the directory is empty except Stored? Metadata in the File for . and .. Metadata in the Directory ■ Then delete it the same way a normal file is Crash Recovery
The Unix Filesystem deleted File Operations ■ But – the link count in the parent directory is Opening a File Creating a File decremented Reading a File Writing a File ■ It’s possible to delete the current working Seek Closing a File directory, or even its parent! Linking to a File Unlinking a File Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 29 / 42 Renaming
Linux Metadata ■ Where is Metadata Create a link with the new name Stored? Metadata in the File ■ Remove the link with the old name Metadata in the Directory ■ But — it must be done in the kernel, since the Crash Recovery
The Unix Filesystem first step involves creating a hard link to a File Operations directory Opening a File Creating a File Reading a File Writing a File Seek Closing a File Linking to a File Unlinking a File Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 30 / 42 I’ve Glossed Over Stuff
Linux Metadata ■ Where is Metadata There’s a fair mount of locking going on, to Stored? Metadata in the File ensure consistency Metadata in the Directory ■ I have not mentioned proper order of Crash Recovery
The Unix Filesystem operations to ensure file system consistency File Operations ■ There are a variety of less-important system Opening a File Creating a File calls Reading a File Writing a File ■ File permissions Seek Closing a File ■ Special files and symbolic links Linking to a File Unlinking a File Updating Metadata Creating Directories Deleting Directories Renaming I’ve Glossed Over Stuff
File System Layout The Windows FAT File System
Dump/Restore 31 / 42 Components of a File System
Linux Metadata ■ Where is Metadata Boot record, superblock Stored? Metadata in the File ■ i-list Metadata in the Directory ■ Freelist Crash Recovery ■ The Unix Filesystem Data area
File Operations
File System Layout Components of a File System Boot Record and Superblock The I-List Data Area The Windows FAT File System
Dump/Restore
32 / 42 Boot Record and Superblock
Linux Metadata ■ Where is Metadata The boot record is at the start of the disk; it’s Stored? Metadata in the File used by the BIOS for booting (called the Metadata in the Directory Master Boot Record (MBR) on PCs) Crash Recovery ■ The Unix Filesystem This area also stores the disk label — File Operations information on how the disk is partitioned File System Layout ■ Components of a Next is the superblock — contains essential File System Boot Record and file system parameters Superblock The I-List ■ Among other things: how to find the i-list; the Data Area The Windows FAT “clean shutdown” flag, to indicate that the file File System
Dump/Restore system is believed to be in a consistent state
33 / 42 The I-List
Linux Metadata ■ Where is Metadata Once, the i-list was an array of blocks just Stored? Metadata in the File after the superblock Metadata in the Directory ■ Today, it’s distributed — a piece of the i-list is Crash Recovery
The Unix Filesystem in each cylinder group File Operations ■ A cylinder group contains a portion of the File System Layout Components of a i-list, a freelist for blocks within the cylinder File System Boot Record and group, and a data area Superblock The I-List ■ Newly-created files get their initial block Data Area The Windows FAT allocations within the cylinder group; later File System
Dump/Restore blocks are allocated in groups in other cylinder groups ■ What is the purpose of cylinder groups? ■ Locality of reference — try to avoid long seeks
34 / 42 Data Area
Linux Metadata ■ Where is Metadata Most of the file is allocated in blocks of 4-8K Stored? Metadata in the File bytes Metadata in the Directory ■ Left-over pieces of the file are stored in Crash Recovery
The Unix Filesystem fragments, which are composed of 512-byte File Operations blocks File System Layout ■ Components of a Dual block size saves RAM and disk space for File System Boot Record and large files, but doesn’t waste too much for Superblock The I-List short files Data Area The Windows FAT File System
Dump/Restore
35 / 42 The Windows FAT File System
Linux Metadata ■ Where is Metadata Limited-size root directory Stored? Metadata in the File ■ 8.3 file names Metadata in the Directory ■ Metadata in the directory entry Crash Recovery ■ The Unix Filesystem Directory points to FAT table entry
File Operations
File System Layout The Windows FAT File System The Windows FAT File System File Allocation Table Supporting Long Names
Dump/Restore
36 / 42 File Allocation Table
Linux Metadata ■ Where is Metadata The FAT keeps track of allocated blocks Stored? Metadata in the File ■ Each entry in the FAT — on disk and in RAM Metadata in the Directory — is just a pointer to the next block Crash Recovery ■ The Unix Filesystem Implements a linked list of blocks, without the File Operations need to read each block File System Layout ■ Maximum file size limited by number of bits in The Windows FAT File System The Windows FAT a disk block address — current is using 28-bit File System File Allocation Table addresses Supporting Long Names
Dump/Restore
37 / 42 Supporting Long Names
Linux Metadata ■ Where is Metadata For Windows 98, they wanted to support Stored? Metadata in the File longer names than 8.3 permitted Metadata in the Directory ■ But — must maintain substantial name Crash Recovery
The Unix Filesystem compatibility with older versions of Windows File Operations and DOS File System Layout ■ First: use recognizable part of long name for The Windows FAT File System The Windows FAT 8.3 version File System ■ File Allocation Table Second: create fake, invalid directory entries Supporting Long Names that precede the real one Dump/Restore ■ DOS will ignore them, because they appear invalid ■ Have a checksum in case the real, short-name version of the file is deleted while running DOS
38 / 42 Dumping a Disk
Linux Metadata ■ Where is Metadata Must have a way to dump and restore disks — Stored? Metadata in the File some people make backups Metadata in the Directory ■ More than — we want a way to to create Crash Recovery
The Unix Filesystem incremental dumps: all files changed since the File Operations last dump File System Layout ■ Unix has multiple levels of backup: 0 is The Windows FAT File System everything; 1 is everything since the last level Dump/Restore Dumping a Disk 1; 2 is everything since the last level 1; etc. Dump Strategies Mapping a ■ Can select files by date modified or by a Filesystem Dumping a Filesystem “dirty” bit ■ Some systems have a way to exclude some files from being dump (i.e., swap files or very sensitive files)
39 / 42 Dump Strategies
Linux Metadata ■ Where is Metadata Could do a physical image dump Stored? Metadata in the File ■ Safe and simple, but wasteful — dumps empty Metadata in the Directory blocks, can’t do incremental dump, might try Crash Recovery
The Unix Filesystem to dump bad blocks, etc. File Operations ■ only restorable to disk with identical geometry File System Layout ■ Instead — dump a filesystem The Windows FAT File System
Dump/Restore Dumping a Disk Dump Strategies Mapping a Filesystem Dumping a Filesystem
40 / 42 Mapping a Filesystem
Linux Metadata ■ Where is Metadata Must map the file system to see what files Stored? Metadata in the File must be dumped Metadata in the Directory ■ For incremental dumps, must be able to Crash Recovery
The Unix Filesystem “dump” deletions — those are changes to the File Operations parent directory File System Layout ■ Must also dump all parent directories, up to The Windows FAT File System the root, of any dumped files Dump/Restore Dumping a Disk ■ Dump selection is based on metadata (and Dump Strategies Mapping a metadata must be dmped) Filesystem Dumping a Filesystem
41 / 42 Dumping a Filesystem
Linux Metadata ■ Where is Metadata The actual dump can’t go through the file Stored? Metadata in the File system on Unix; want to avoid dumping file Metadata in the Directory system “holes” Crash Recovery ■ The Unix Filesystem The actual dump file is based on i-node File Operations numbers, not file names; the file names are in File System Layout the dumped directories The Windows FAT File System ■ Restores can be done through the file system Dump/Restore Dumping a Disk ■ To do incremental restores, must restore each Dump Strategies Mapping a level in sequence, to build the proper directory Filesystem Dumping a Filesystem structure
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