Centos的Inode及Block相关知识
本经验均在CentOSrelease6.7(Final)下操作,如知识有欠缺之处 欢迎批评指正。
linux 的inode及block的相关知识:
1> Linux系统分区格式化文件系统之后,系统会分为Inode及Block两部分:
1)Inode为系统文件的属性信息(ls -l的结果)及指向文件实体的指针,但是没有存放文件名,一般在上级目录里的Block。
2)Block为存放数据的,ext3/ext4一般为1k,2k,4k,一般默认4k
3)一个文件不论多大至少占用一个Inode和一个Block,一个Block只能存放一个文件的内容,block的数量大于Inode的数量,多个文件可以占用同一个 inode(硬链接) 。
4)访问文件, 通过文件-->inode(验证权限)--->blocks.
5)inode 一般情况默认256B,block大小1k,2k,4k,默认4k,注意,引导分区等特殊分区除外。
6)通过df -i 查看inode的数量及使用情况,dumpe2fs /dev/sda1 查看inode及block的大小和数量。
7)一个block只能 被一个文件使用 ,如果一个文件很小block太大,剩余空间浪费,无法继续被其他文件使用。
8)block不是越大越好,根据业务的文件大小进行选择,一般就是默认 4k。
9)可以在格式化的时候改变inode及block的大小,使用mkfs.ext4 -b 2048 -I 1024 /dev/sdb2
2>Linux中df命令的功能是用来检查linux服务器的文件系统的磁盘空间占用情况。可以利用该命令来获取硬盘被占用了多少空间,目前还剩下多少空间等信息。
1.命令格式:
df [选项] [文件]
2.参数 :
df -i 查看参数多少 个
[root@techW ~]
# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/mapper/vg_techw-lv_root
1152816 55846 1096970 5% /
tmpfs 125596 1 125595 1%
/dev/shm
/dev/sda1
128016 38 127978 1%
/boot
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df -h 查看磁盘大小:
[root@techW ~]
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_techw-lv_root
18G 1.5G 15G 9% /
tmpfs 491M 0 491M 0%
/dev/shm
/dev/sda1
477M 36M 416M 8%
/boot
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查看当前系统分区的Inode及Block的总量及使用量:
[root@techW ~]
# dumpe2fs /dev/sda1 | grep -i "block size"
dumpe2fs 1.41.12 (17-May-2010)
Block size: 1024
[root@techW ~]
#
[root@techW ~]
#
[root@techW ~]
# dumpe2fs /dev/sda1 | grep -i "inode size"
dumpe2fs 1.41.12 (17-May-2010)
Inode size: 128
###boot分区为128,常规分区为256
[root@techW ~]
#
[root@techW ~]
#
[root@techW ~]
# dumpe2fs /dev/sda1 | grep -i "inode count"
dumpe2fs 1.41.12 (17-May-2010)
Inode count: 128016
[root@techW ~]
#
[root@techW ~]
# dumpe2fs /dev/sda1 | grep -i "block count"
dumpe2fs 1.41.12 (17-May-2010)
Block count: 512000
Reserved block count: 25600
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3>添加一块磁盘,格式化,改变Inode及 Block的大小,挂载查看硬盘的Inode及Block数量:
1)添加一块5G的磁盘,为方便区分设置为/dev/sdb,fdisk分区,然后mkfs.ext4格式化
(虚拟机增加一块5G的硬盘,分区,格式化)
[root@techW ~]
# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x2d37eabe.
Changes will remain
in
memory only,
until
you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (
command
'c'
) and change display
units
to
sectors (
command
'u'
).
Command (m
for
help): n
### add a new partition
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
### 为做区分,选择2
First cylinder (1-652, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-652, default 652):
Using default value 652
Command (m
for
help): w
### write table to disk and exit
The partition table has been altered!
Calling ioctl() to re-
read
partition table.
Syncing disks.
分区时的参数命令:
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system
id
u change display
/entry
units
v
verify the partition table
w write table to disk and
exit
x extra functionality (experts only)
|
[root@techW ~]
# mkfs.ext4 /dev/sdb2
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS
type
: Linux
Block size=4096 (log=2)
###默认的Block的大小为4096
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
327680 inodes, 1309289 blocks
65464 blocks (5.00%) reserved
for
the super user
First data block=0
Maximum filesystem blocks=1342177280
40 block
groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736
Writing inode tables:
done
Creating journal (32768 blocks):
done
Writing superblocks and filesystem accounting information:
done
This filesystem will be automatically checked every 26 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
|
2)###inode的大小范围为128-2048,block的大小范围为1024-4096####
3)将Block和Inode的大小都改为2048:
[root@techW ~]
# mkfs.ext4 -b 2048 -I 2048 /dev/sdb2
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS
type
: Linux
Block size=2048 (log=1)
Fragment size=2048 (log=1)
Stride=0 blocks, Stripe width=0 blocks
326400 inodes, 2618578 blocks
130928 blocks (5.00%) reserved
for
the super user
First data block=0
Maximum filesystem blocks=540016640
160 block
groups
16384 blocks per group, 16384 fragments per group
2040 inodes per group
Superblock backups stored on blocks:
16384, 49152, 81920, 114688, 147456, 409600, 442368, 802816, 1327104,
2048000
Writing inode tables:
done
Creating journal (32768 blocks):
done
Writing superblocks and filesystem accounting information:
done
This filesystem will be automatically checked every 30 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
|
4)使用dumpe2fs命令查询Inode和Block的大小:
[root@techW ~]
# dumpe2fs /dev/sdb2 | grep "Inode size"
dumpe2fs 1.41.12 (17-May-2010)
Inode size: 2048
###大小更改成功
[root@techW ~]
#
s
/dev/sdb2
|
grep
"Block size"
dumpe2fs 1.41.12 (17-May-2010)
Block size: 2048
###大小更改成功
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