一、先删除fdisk模拟分区的四个盘
[root@qiqi~]#fdisk /dev/sdb
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): d #<--删除分区
Partition number (1-5): 1 #<--删除编号为1的分区
Command (m for help): d
Partition number (1-5): 2
Command (m for help): p
Disk /dev/sdb: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x3f0ec866
Device Boot Start End Blocks Id System
/dev/sdb3 61 80 160650 5 Extended
/dev/sdb4 1 20 160618+ 83 Linux
Partition table entries are not in disk order
Command (m for help): d
Partition number (1-5): 3
Command (m for help): d
Selected partition 4 #<--3为扩展分区已删除，4也随之删除。
Command (m for help): 4
4: unknown command
Command (m for help): w #<--保存修改
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
二、知识简介
1、磁盘大于2T使用parted 创建分区，当一个分区大小超过2T时, 不能再使用MBR引导记录, 使用GPT来识别大容量磁盘，命令行输入：
#parted /dev/sdd #<--交互式开始分区
2、分区方法:
①mklabel（创建分区表 MRB-msdos/gpt）#<--修改分区格式gpt create a new disklabel (partition table) mklabel gpt
②mkpart （创建新的分区） make a partition
mkpart primary 0 20M #<--创建第一个主分区
③print（显示分区表信息）
display the partition table
④rm（删除指定分区信息）
delete partition NUMBER
quit（退出分区界面）
exit program
3、
①(parted) mklabel gpt #<--修改分区引导记录信息 Warning: Partition(s) on /dev/sdd are being used.
Ignore/Cancel? Ignore
②(parted) mkpart primary 0 200M #<--输入分区大小 创建分区信息
删除分区方法(parted)rm 分区号码
③在格式化前需要执行以下命令
#partprobe /dev/sdb （你分区的全路径名称） #<--- 告知内核系统已经对磁盘进行了分区
文件系统有什么: 采用相应机制存储和管理数据
centos5: ext2 ext3
centos6: ext4
centos7: xfs
特点: 在数据库服务器中可以更高效存储数据信息
在格式化磁盘时, 效率更高(大的磁盘)
nfs 网络文件系统 分布式文件系统
做格式化处理:
#mkfs.ext4 /dev/sdb1#<--格式化ext4文件系统 mkfs.ext4其实关键就是生成一定数量的Inode和Block。
mkfs.xfs /dev/sdb1 --- 无法识别小分区信息(10M以下)
#mkfs -t xfs /dev/sdb1
④进行磁盘挂载
#mount /dev/sdb1 /mnt 临时挂载重启失效
如何实现自动挂载分区(/dev/sdc1 /mnt_100M)
mount /dev/sdc1 /mnt_100M
方法一: 将挂载命令放入到/etc/rc.local文件中
#vim /etc/rc.local
输入：mount /dev/sdc1 /mnt_100M
说明：没有格式化没法挂载
cat /proc/mounts #查看挂载结果
umount -lf /mnt #<==强制卸载
df -h #查看挂载结果
说明: 需要确保rc.local目录具有执行权限
# ll -d /etc/rc.local
lrwxrwxrwx. 1 root root 13 Dec 29 16:33 /etc/rc.local -> rc.d/rc.local
# ll -d /etc/rc.d/rc.local
-rwxr-xr-x. 1 root root 499 Jan 29 11:33 /etc/rc.d/rc.local
方法二: 利用fstab文件实现分区自动挂载
vim /etc/fstab
设备文件 挂载点目录 文件系统类型 挂载的参数信息 是否进行备份 是否检查磁盘
/dev/sdc1 /mnt_100M xfs defaults 0 0
三、企业案例:
tomcat(网站服务)--java语言编写的程序, 运行过程中比较消耗内存
临时需要添加内存 --- 将硬盘空间临时充当内存使用 -- swap分区
如何调正swap分区大小
从磁盘中取出一定空间重当内存使用
命令行输入：
#dd if=/dev/zero of=/tmp/1G bs=100M count=10
10+0 records in
10+0 records out
1048576000 bytes (1.0 GB) copied, 25.9294 s, 40.4 MB/s
root@qiqi~]# blkid 查看磁盘挂载信息
/dev/sdb1: UUID="a45b004f-2322-4dc4-a281-2a212dd2ab79" TYPE="ext4"
/dev/sdb2: UUID="7daf8142-b641-4b60-a287-4e08dfa18611" TYPE="xfs"
/dev/sda1: UUID="fd2e0ca7-32be-425f-86a2-85c02b9ec5ea" TYPE="xfs"
/dev/sda2: UUID="79a3924b-739e-48dc-ab0c-0444b9ac6591" TYPE="swap"
/dev/sda3: UUID="3a3a295f-88f8-456d-94dc-1a3eeb517c02" TYPE="xfs"
mount -a 可以将fstab里的信息挂载。
放入/etc/rc.local 实现自动挂载 但不推荐。
/sbin/mount -t xfs /dev/sdb2 /opt
查看文件系统内部细节：
[root@qiqi~]# dumpe2fs /dev/sdb1 #查看ext文件系统内部细节
[root@qiqi~]# dumpe2fs /dev/sdb1|egrep -i "size"
dumpe2fs 1.42.9 (28-Dec-2013)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super huge_file uninit_bg dir_nlink extra_isize
Block size: 1024
Fragment size: 1024
Group descriptor size: 64
Flex block group size: 16
Inode size: 128
Journal size: 4096k
指定块大小和inode大小格式:
[root@qiqi~]# mkfs -t ext4 -b 4096 -I 512 /dev/sdb3
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
38400 inodes, 38400 blocks
1920 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=39845888
2 block groups
32768 blocks per group, 32768 fragments per group
19200 inodes per group
Superblock backups stored on blocks:
32768
Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
[root@qiqi~]# dumpe2fs /dev/sdb3|egrep -i "size"
dumpe2fs 1.42.9 (28-Dec-2013)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Block size: 4096
Fragment size: 4096
Group descriptor size: 64
Flex block group size: 16
Inode size: 512
Required extra isize: 28
Desired extra isize: 28
Journal size: 16M
文件删除原理：
no space left on device. 磁盘容量不足
swap作用，内存不够时候，用来充当内存，一般内存1.5倍。大于8G给8G
将来JAVA服务，内存泄漏。。。
swap就会占用。。。操作系统性能下降
[root@qiqi~]# free -m
total used free shared buff/cache available
Mem: 1980 143 1689 9 146 1671
Swap: 767 0 767
增加swap分区 100M
[root@qiqi~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): n
Partition type:
p primary (3 primary, 0 extended, 1 free)
e extended
Select (default e): p
Selected partition 4
First sector (718848-2097151, default 718848):
Using default value 718848
Last sector, +sectors or +size{K,M,G} (718848-2097151, default 2097151): +150M
Partition 4 of type Linux and of size 150 MiB is set
Command (m for help): p
Disk /dev/sdb: 1073 MB, 1073741824 bytes, 2097152 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
Disk label type: dos
Disk identifier: 0x000006b6
Device Boot Start End Blocks Id System
/dev/sdb1 2048 206847 102400 83 Linux
/dev/sdb2 206848 411647 102400 83 Linux
/dev/sdb3 411648 718847 153600 83 Linux
/dev/sdb4 718848 1026047 153600 83 Linux
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
[root@qiqi~]# partprobe /dev/sdb
[root@qiqi~]# mkswap /dev/sdb4
Setting up swapspace version 1, size = 153596 KiB
no label, UUID=2d1ac352-4cc0-4727-8318-5526a3c309c2
[root@qiqi~]# swapon -a /dev/sdb4
You have new mail in /var/spool/mail/root
[root@qiqi~]# free -m
total used free shared buff/cache available
Mem: 1980 144 1673 19 162 1658
Swap: 917 0 917
四、fsck 磁盘检查和修复
1、正常的磁盘不能操作。
2、卸载挂载点在操作
[root@qiqi~]# fsck
fsck fsck.btrfs fsck.cramfs fsck.ext2 fsck.ext3 fsck.ext4 fsck.minix fsck.xfs
[root@qiqi~]# fsck -a /dev/sdb1
fsck from util-linux 2.23.2
/dev/sdb1: clean, 12/25688 files, 8896/102400 blocks
[root@qiqi~]# mount /dev/sdb1 /mnt
[root@qiqi~]# fsck -a /dev/sdb1
fsck from util-linux 2.23.2
/dev/sdb1 is mounted.
e2fsck: Cannot continue, aborting.
[root@qiqi~]# e2fsck /dev/sdb1
e2fsck 1.42.9 (28-Dec-2013)
/dev/sdb1: clean, 12/25688 files, 8896/102400 blocks
[root@qiqi~]# fsck -a /dev/sdb1
fsck from util-linux 2.23.2
/dev/sdb1: clean, 12/25688 files, 8896/102400 blocks
[root@qiqi~]# xfs_repair /dev/sdb2
xfs_repair: /dev/sdb2 contains a mounted filesystem
xfs_repair: /dev/sdb2 contains a mounted and writable filesystem
fatal error -- couldn't initialize XFS library
[root@qiqi~]# umount /opt
[root@qiqi~]# xfs_repair /dev/sdb2
Phase 1 - find and verify superblock...
Phase 2 - using internal log
- zero log...
- scan filesystem freespace and inode maps...
- found root inode chunk
Phase 3 - for each AG...
- scan and clear agi unlinked lists...
- process known inodes and perform inode discovery...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
- process newly discovered inodes...
Phase 4 - check for duplicate blocks...
- setting up duplicate extent list...
- check for inodes claiming duplicate blocks...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
Phase 5 - rebuild AG headers and trees...
- reset superblock...
Phase 6 - check inode connectivity...
- resetting contents of realtime bitmap and summary inodes
- traversing filesystem ...
- traversal finished ...
- moving disconnected inodes to lost+found ...
Phase 7 - verify and correct link counts...
done
