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MentOS
0.8.0
The Mentoring Operating System
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The superblock contains all the information about the configuration of the filesystem. More...
Public Attributes | |
| uint32_t | inodes_count |
| Total number of inodes in file system. | |
| uint32_t | blocks_count |
| Total number of blocks in file system. | |
| uint32_t | r_blocks_count |
| Number of blocks reserved for superuser. | |
| uint32_t | free_blocks_count |
| Total number of unallocated blocks. | |
| uint32_t | free_inodes_count |
| Total number of unallocated inodes. | |
| uint32_t | first_data_block |
| Block number of the block containing the superblock. | |
| uint32_t | log_block_size |
| The number to shift 1024 to the left by to obtain the block size (log2 (block size) - 10). | |
| uint32_t | log_frag_size |
| The number to shift 1024 to the left by to obtain the fragment size (log2 (fragment size) - 10). | |
| uint32_t | blocks_per_group |
| Number of blocks in each block group. | |
| uint32_t | frags_per_group |
| Number of fragments in each block group. | |
| uint32_t | inodes_per_group |
| Number of inodes in each block group. | |
| uint32_t | mtime |
| Last mount time (in POSIX time). | |
| uint32_t | wtime |
| Last written time (in POSIX time). | |
| uint16_t | mnt_count |
| Number of times the volume has been mounted since its last consistency check (fsck). | |
| uint16_t | max_mnt_count |
| Number of mounts allowed before a consistency check (fsck) must be done. | |
| uint16_t | magic |
| Ext2 signature (0xef53), used to help confirm the presence of Ext2 on a volume. | |
| uint16_t | state |
| File system state. | |
| uint16_t | errors |
| What to do when an error is detected. | |
| uint16_t | minor_rev_level |
| Minor portion of version (combine with Major portion below to construct full version field). | |
| uint32_t | lastcheck |
| POSIX time of last consistency check (fsck). | |
| uint32_t | checkinterval |
| Interval (in POSIX time) between forced consistency checks (fsck). | |
| uint32_t | creator_os |
| Operating system ID from which the filesystem on this volume was created. | |
| uint32_t | rev_level |
| Major portion of version (combine with Minor portion above to construct full version field). | |
| uint16_t | def_resuid |
| User ID that can use reserved blocks. | |
| uint16_t | def_resgid |
| Group ID that can use reserved blocks. | |
| uint32_t | first_ino |
| First non-reserved inode in file system. (In versions < 1.0, this is fixed as 11) | |
| uint16_t | inode_size |
| Size of each inode structure in bytes. (In versions < 1.0, this is fixed as 128) | |
| uint16_t | block_group_nr |
| Block group that this superblock is part of (if backup copy). | |
| uint32_t | feature_compat |
| Optional features present (features that are not required to read or write, but usually result in a performance increase). | |
| uint32_t | feature_incompat |
| Required features present (features that are required to be supported to read or write) | |
| uint32_t | feature_ro_compat |
| Features that if not supported, the volume must be mounted read-only). | |
| uint8_t | uuid [16] |
| File system ID (what is output by blkid). | |
| uint8_t | volume_name [16] |
| Volume name (C-style string: characters terminated by a 0 byte). | |
| uint8_t | last_mounted [64] |
| Path volume was last mounted to (C-style string: characters terminated by a 0 byte). | |
| uint32_t | algo_bitmap |
| Compression algorithms used. | |
| uint8_t | prealloc_blocks |
| Number of blocks to preallocate for files. | |
| uint8_t | prealloc_dir_blocks |
| Number of blocks to preallocate for directories. | |
| uint16_t | padding0 |
| (Unused) | |
| uint8_t | journal_uuid [16] |
| Journal ID. | |
| uint32_t | journal_inum |
| Inode number of journal file. | |
| uint32_t | jounral_dev |
| Device number of journal file. | |
| uint32_t | last_orphan |
| Start of list of inodes to delete. | |
| uint32_t | hash_seed [4] |
| HTree hash seed. | |
| uint8_t | def_hash_version |
| Ddefault hash version to use. | |
| uint16_t | padding1 |
| Padding. | |
| uint8_t | padding2 |
| Padding. | |
| uint32_t | default_mount_options |
| The default mount options for the file system. | |
| uint32_t | first_meta_block_group_id |
| The ID of the first meta block group. | |
| uint8_t | reserved [760] |
| Reserved. | |
The superblock contains all the information about the configuration of the filesystem.
The primary copy of the superblock is stored at an offset of 1024 bytes from the start of the device, and it is essential to mounting the filesystem. Since it is so important, backup copies of the superblock are stored in block groups throughout the filesystem.
1.9.1