inodes. filesystems each partition has a filesystem –this filesystem will usually support a...
TRANSCRIPT
inodes
Filesystems• Each partition has a filesystem
– This filesystem will usually support a directory hierarchy
• Every file on a disk partition is allocated an inode number.– Typically this is an index number into an array stored on that disk– Each element in that array is an inode
• inodes store administrative information about a file– Who created it– When it was created– Etc
• inode numbers are stored alongside the filename in the directory– This means directories are tables that associate filenames with inode
numbers
dir1
dir2
file1
file2
file98
file97
1301
1306
1997
2675
An actual inode
1301
1306
1302
1307
1303
1304
1305
filesystem
location on H/D, owner:pdunne, size:2M, etc
location on H/D ,owner:pdunne, size:200K
inode numberfilename
filename inode number
Each filename – inode pair is called a link
The same inode number can appear in more than one link
The inode number is the indexnumber in the inode array
1997
1997
dir1
dir2
file1
file2
file99
file98
file97
1301
1306
1306
1997
2675
The actual inode
1301
1306
1302
1307
1303
1304
1305
filesystem
location on H/D, owner:pdunne, size:2M, etc
location on H/D ,owner:pdunne, size:200K
inode numberfilename
filename inode number
The inode number is the indexnumber in the inode array
Here we have two linksto the same inode
Hard link: Associate two or more file names with the same inode. Hard links share the same data blocks on the hard disk, while they continue to behave as independent files….If you delete one link the other link still points to inode
1997
Create a hard link$ ln TARGET LINK_NAME$ ln /dir1/file1 /dir2/file99
Create a hard link$ ln TARGET LINK_NAME$ ln /dir1/file1 /dir2/file99
dir1
dir2
file1
file2
file99
file98
file97
1301
1306
1997
2675
The actual inode
1301
1306
1302
1307
1303
1304
1305
filesystem
location on H/D, owner:pdunne, size:2M, etc
location on H/D ,owner:pdunne, size:200K
inode numberfilename
filename inode number
The inode number is the indexnumber in the inode array
Here we have two linksto the same inode
Soft link or symbolic link (or for short: symlink): a small file that is a pointer (i.e. contains path) to another file. All commands that read/write follow a link follow and operate on the real file. Symbolic links can span partitions!
1997
dir1
dir2
file1
file2
file99
file98
file97
1301
1306
1306
1997
2675
The actual inode
1301
1306
1302
1307
1303
1304
1305
filesystem
location on H/D, owner:pdunne, size:2M, etc
location on H/D ,owner:pdunne, size:200K
inode numberfilename
filename inode number
Each filename – inode pair is called a link
The inode number is the indexnumber in the inode array
Here we have two linksto the same inode
$ rm /dir1/file1
The direcory link is removed, inode is released and file H/D data blocks released
1997
X
dir1
dir2
file1
file2
file99
file98
file97
1301
1306
1306
1997
2675
The actual inode
1301
1306
1302
1307
1303
1304
1305
filesystem
location on H/D, owner:pdunne, size:2M, etc
location on H/D ,owner:pdunne, size:200K
inode numberfilename
filename inode number
The inode number is the indexnumber in the inode array
Here we have two linksto the same inode
$mv /dir1/file1 /dir1/fileABC The move command, mv, can be used to rename a file if the second parameter is in the same directory as the original file. It creates a new entry with the same inode and then deletes the old link.
1997
fileABC 1301
X