Metadata is data about data. Data is basically the same thing as information, although it is often in a form that is easier for humans and/or computers to use and manipulate.
Major functions of computer filesystems are the storing of metadata about files and facilitating the locating and manipulation of files. The metadata about a file on a Unix-like operating system includes its file type (e.g., data file, directory, link), name, timestamps (i.e., dates of creation, last access and modification), location on the filesystem, size (in bytes), its physical location (i.e., the addresses of the blocks of storage containing the file’s data on a disk), ownership (usually the same as its creator), access permissions (i.e., which users are permitted to read, write and/or execute the file) and file type.
An inode is a data structure on a Unix-like operating system that stores all the metadata about a file except its name(s); the name(s) and the actual data of the file are stored elsewhere. A data structure is a way of storing information in a computer so that it can be used efficiently.
An inode is a data structure on a file-system on Linux and other Unix-like operating systems that stores all the information about a file except its name and its actual data.
Inode is a structure contains the information necessary for a process to access a file. Exist in a static form on disk and the kernel reads them into an in-core inode consists of:
- file owner identifier.
- file type.
- file access permissions.
- file access times.
- number of links to the file.
- table of contents for the disk address of data in a file.
- file size.
Inode Contains all the details about a file like owner, permission, type etc. But it doesn’t Contain the “Filename” for the particular file.
A data structure is a way of storing data so that it can be used efficiently. Different types of data structures are suited to different types of applications, and some are highly specialized for specific types of tasks.
Superblock
The superblock is a structure that represents a file system. It includes the necessary information to manage the file system during operation. It includes the file system name (such as ext2), the size of the file system and its state, a reference to the block device, and metadata information (such as free lists and so on). The superblock is typically stored on the storage medium but can be created in real time if one doesn’t exist.
Finding out the backup superblock.
root@dell:~# dumpe2fs /dev/sda2 |grep -i superblock
dumpe2fs 1.41.2 (02-Oct-2008)
Primary superblock at 0, Group descriptors at 1-3
Backup superblock at 32768, Group descriptors at 32769-32771
Backup superblock at 98304, Group descriptors at 98305-98307
Backup superblock at 163840, Group descriptors at 163841-163843
Backup superblock at 229376, Group descriptors at 229377-229379
Backup superblock at 294912, Group descriptors at 294913-294915
Backup superblock at 819200, Group descriptors at 819201-819203
Backup superblock at 884736, Group descriptors at 884737-884739
Backup superblock at 1605632, Group descriptors at 1605633-1605635
Backup superblock at 2654208, Group descriptors at 2654209-2654211
Backup superblock at 4096000, Group descriptors at 4096001-4096003
Backup superblock at 7962624, Group descriptors at 7962625-7962627
TCP Connections by State
TCP Connections by State probe identifies the total number of TCP connections, as well as the quantity of each in the following states:
TIME_WAIT — The socket is waiting after close for remote shutdown transmission so it may handle packets still in the network.
CLOSE_WAIT — The remote side has been shut down and is now waiting for the socket to close.
FIN_WAIT — The socket is closed, and the connection is now shutting down.
ESTABLISHED — The socket has a connection established.
SYN_RCVD — The connection request has been received from the network.
Shared Memory?
Shared memory (SHM) is another method of interprocess communication (IPC) whereby 2 or more processes share a single chunk of memory to communicate. The shared memory system can also be used to set permissions on memory, allowing for things like malloc debuggers to be written.
Types of Shared memory available
Basically there are two different types of shared memory available for most flavors of UNIX. As you may have guessed, each of the two orignal ancestors of modern UNIX have their own implementation, altough almost all modern UNIX flavors implement both. The names of the respective implementations are System V IPC, and BSD mmap.
