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The default options for the command are stored in the file mke2fs.conf, usually in the /etc directory. Depending on the implementation and the specific file system requested, the command may have many options that can be specified such as inode size, block size, volume label, and other features. [7] (See file system for details)
save critical ext2/ext3/ext4 filesystem metadata to a file e2label change the label on an ext2/ext3/ext4 filesystem e2scrub check a filesystem "online" (i.e. without having to unmount it) in the case where the filesystem is on an LVM LV e2undo replay an undo log for an ext2/ext3/ext4 filesystem e4defrag online defragmenter for ext4 filesystem ...
A more common use case is the invocation of badblocks as part of e2fsck when passing the option "-c" to scan for bad blocks and prevent data from being stored on these blocks. This is done by adding the list of found bad blocks to the bad block inode to prevent the affected sectors from being allocated to a file or directory.
The Linux kernel allows extended attribute to have names of up to 255 bytes and values of up to 64 KiB, [15] as do XFS and ReiserFS, but ext2/3/4 and btrfs impose much smaller limits, requiring all the attributes (names and values) of one file to fit in one "filesystem block" (usually 4 KiB).
A block, a contiguous number of bytes, is the minimum unit of storage that is read from and written to a disk by a disk driver.The earliest disk drives had fixed block sizes (e.g. the IBM 350 disk storage unit (of the late 1950s) block size was 100 six-bit characters) but starting with the 1301 [8] IBM marketed subsystems that featured variable block sizes: a particular track could have blocks ...
ext4 (fourth extended filesystem) is a journaling file system for Linux, developed as the successor to ext3.. ext4 was initially a series of backward-compatible extensions to ext3, many of them originally developed by Cluster File Systems for the Lustre file system between 2003 and 2006, meant to extend storage limits and add other performance improvements. [4]
With larger disks and larger files, fragmented reads became more of a problem. To combat this, BSD originally increased the filesystem block size from one sector to 1 K in 4.0 BSD; and, in FFS, increased the filesystem block size from 1 K to 8 K. This has several effects. The chance of a file's sectors being contiguous is much greater.
The reason for some limits of ext2 are the file format of the data and the operating system's kernel. Mostly these factors will be determined once when the file system is built. They depend on the block size and the ratio of the number of blocks and inodes. [citation needed] In Linux the block size is limited by the architecture page size.