前言
debugfs是e2fsprogs安装后的工具，这个工具的参数好多，而且是交互式输入命令，不是带参数执行完就了事。
实验
先用fdisk确定要操作的磁盘
root@localhost:/home/e2_install/sbin# fdisk -l
Disk /dev/sda: 120 GiB, 128849018880 bytes, 251658240 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xfed8ebe5
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 247463935 247461888 118G 83 Linux
/dev/sda2 247465982 251656191 4190210 2G 5 Extended
/dev/sda5 247465984 251656191 4190208 2G 82 Linux swap / Solaris
Disk /dev/sdb: 30.1 MiB, 31555584 bytes, 61632 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x2dac66d5
Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 61631 59584 29.1M 83 Linux
能看到自己的实验小U盘为 /dev/sdb1
对选定磁盘使用debugfs
root@localhost:/home/e2_install/sbin# debugfs /dev/sdb1
debugfs 1.45.0 (6-Mar-2019)
debugfs:
看看帮助
带硬盘全路径启动后，进入的式交互式UI. 这时不看帮助就不知道咋弄了。
平直觉，输入一个help, 回车，我真机智:)
帮助出来后，如果显示不完，按下回车不放，让帮助显示完。
debugfs: help
Available debugfs requests:
show_debugfs_params, params
Show debugfs parameters
open_filesys, open Open a filesystem
close_filesys, close Close the filesystem
freefrag, e2freefrag Report free space fragmentation
feature, features Set/print superblock features
dirty_filesys, dirty Mark the filesystem as dirty
init_filesys Initialize a filesystem (DESTROYS DATA)
show_super_stats, stats Show superblock statistics
ncheck Do inode->name translation
icheck Do block->inode translation
change_root_directory, chroot
Change root directory
change_working_directory, cd
Change working directory
list_directory, ls List directory
show_inode_info, stat Show inode information
dump_extents, extents, ex
Dump extents information
blocks Dump blocks used by an inode
filefrag Report fragmentation information for an inode
link, ln Create directory link
unlink Delete a directory link
mkdir Create a directory
rmdir Remove a directory
rm Remove a file (unlink and kill_file, if appropriate)
kill_file Deallocate an inode and its blocks
copy_inode Copy the inode structure
clri Clear an inode's contents
freei Clear an inode's in-use flag
seti Set an inode's in-use flag
testi Test an inode's in-use flag
freeb Clear a block's in-use flag
setb Set a block's in-use flag
testb Test a block's in-use flag
modify_inode, mi Modify an inode by structure
find_free_block, ffb Find free block(s)
find_free_inode, ffi Find free inode(s)
print_working_directory, pwd
Print current working directory
expand_dir, expand Expand directory
mknod Create a special file
list_deleted_inodes, lsdel
List deleted inodes
undelete, undel Undelete file
write Copy a file from your native filesystem
dump_inode, dump Dump an inode out to a file
cat Dump an inode out to stdout
lcd Change the current directory on your native filesystem
rdump Recursively dump a directory to the native filesystem
set_super_value, ssv Set superblock value
set_inode_field, sif Set inode field
set_block_group, set_bg Set block group descriptor field
logdump Dump the contents of the journal
htree_dump, htree Dump a hash-indexed directory
dx_hash, hash Calculate the directory hash of a filename
dirsearch Search a directory for a particular filename
bmap Calculate the logical->physical block mapping for an inode
fallocate Allocate uninitialized blocks to an inode
punch, truncate Punch (or truncate) blocks from an inode by deallocating them
symlink Create a symbolic link
imap Calculate the location of an inode
dump_unused Dump unused blocks
set_current_time Set current time to use when setting filesystem fields
supported_features Print features supported by this version of e2fsprogs
dump_mmp Dump MMP information
set_mmp_value, smmp Set MMP value
extent_open, eo Open inode for extent manipulation
zap_block, zap Zap block: fill with 0, pattern, flip bits etc.
block_dump, bdump, bd Dump contents of a block
ea_list List extended attributes of an inode
ea_get Get an extended attribute of an inode
ea_set Set an extended attribute of an inode
ea_rm Remove an extended attribute of an inode
list_quota, lq List quota
get_quota, gq Get quota
inode_dump, idump, id Dump the inode structure in hex
journal_open, jo Open the journal
journal_close, jc Close the journal
journal_write, jw Write a transaction to the journal
journal_run, jr Recover the journal
help Display info on command or topic.
list_requests, lr, ? List available commands.
quit, q Leave the subsystem.
实验命令的用法
关闭设备
debugfs: close
打开设备
open /dev/sdb1
查看磁盘碎片统计
debugfs: freefrag
Device: /dev/sdb1
Blocksize: 1024 bytes
Total blocks: 29792
Free blocks: 27454 (92.2%)
Min. free extent: 4862 KB
Max. free extent: 7839 KB
Avg. free extent: 6863 KB
Num. free extent: 4
HISTOGRAM OF FREE EXTENT SIZES:
Extent Size Range : Free extents Free Blocks Percent
4M... 8M- : 4 27454 100.00%
debugfs:
打印超级块的特性
debugfs: feature
Filesystem features: has_journal ext_attr resize_inode dir_index filetype sparse_super
显示超级块统计信息
debugfs: stats
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 085d84cc-e885-46de-8237-3391bdd37fbc
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype sparse_super
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 7456
Block count: 29792
Reserved block count: 1489
Free blocks: 27454
Free inodes: 7445
First block: 1
Block size: 1024
Fragment size: 1024
Reserved GDT blocks: 116
Blocks per group: 8192
Fragments per group: 8192
Inodes per group: 1864
Inode blocks per group: 233
Filesystem created: Wed Mar 6 18:12:36 2019
Last mount time: n/a
Last write time: Wed Mar 6 18:12:36 2019
Mount count: 0
Maximum mount count: -1
Last checked: Wed Mar 6 18:12:36 2019
Check interval: 0 (<none>)
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 128
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: b0cb4cb3-8838-4dd5-a5a6-d575f4973128
Journal backup: inode blocks
Directories: 2
Group 0: block bitmap at 119, inode bitmap at 120, inode table at 121
7825 free blocks, 1853 free inodes, 2 used directories
Group 1: block bitmap at 8311, inode bitmap at 8312, inode table at 8313
7839 free blocks, 1864 free inodes, 0 used directories
Group 2: block bitmap at 16385, inode bitmap at 16386, inode table at 16387
6928 free blocks, 1864 free inodes, 0 used directories
Group 3: block bitmap at 24695, inode bitmap at 24696, inode table at 24697
4862 free blocks, 1864 free inodes, 0 used directories
当显示END时，按q退出，和在man中的退出是一样的。