fdisk for partitioning

fdisk is based on MBR. So, GPT cannot use fdisk.

fdisk

• only super user can use it.
• fdisk -l can show all the information about disc.
• logical partition always starts with 5.
• sudo fdisk /dev/sd* you can enter the pointed disc. press 'm' for some help
• after updating, use 'partprobe' to let the kernel update the partition table.

d # delete a partition
n # create a new partition. After using all the space for extended partition, you can create logical ones beginning with 5.
# you can use + size {K,M,G,T,P} to decide what the size of the partition is 
w # write the changes to the disc(save)
q # leave without saving.
t # to change the id of a partition.

Linux file system basics

format : the process of creating files.
A device without file system is called raw device.
Common file systems:
fat32 , NTFS , ext2 , ext3 , ext4 , xfs , HFS
Windows: NTFS
Linux: ext3 ext4

what Linux supports?
ext2 ext3 ext4 fat32 ntfs and etc...

to create file sysytem

mke2fs -t ext4 /dev/sda3

common parameters:

-b blocksize # appoint the size of the system block
-c  # check the broken block
-L label # appoint the label (卷标)
-j #establish system log. 

mkfs
It is much simple, but supports few parameters.
mkfs ext4 /dev/sda1

dumpe2fs

get the information about the file system
dumpe2fs /dev/sda2

Journal

with a log,

1. before doing sth, write it down to the log.
2. execute
3. if succeed, the detailed affairs would be deleted.

Of course, the system will get slower with a log. But the system can be much more stable.

e2label

label a partition.

e2label /dev/sda2 #show the label
e2label /dev/sda2 LinuxLabel # name the partition

fsck

check and recover the partition.

fsck /dev/sdb1 # the partition must be uninstalled at first
-y #recover directly without reminding.
-t # if the system was badly hurt, use it.

For those broken data without record, fsck will put them in lost+found file.

MOUNT

mount

you can mount everywhere, but /mnt is recommended.

mount /dev/sda3(partition to mount) /mnt(mount point)
-t type of file system
-o 指定挂载选项
ro, rw 以只读或读写形式挂载，默认是rw
sync 代表不使用缓存，而是对所有操作直接写入磁盘
async 代表使用缓存，默认是async
noatime 代表每次访问文件时不更新文件的访问时间
remount 重新挂载文件系统

umount

umount 文件系统/挂载点
umount /dev/sda3 或者 umount /mnt/

fuser -m /dev/sdb1

哪些进程在使用。

lsof /mnt/

哪些文件杯打开了。

mount automatically

/etc/fstab
/dev/sda3 /mnt ext4 defaults 0 0
对文件系统进行修改，一定先卸载。有卷标也可以用卷标。

ubuntu下的mount

仍然是在/etc/fstab里面配置，但是，要用的dev的UUID.

sudo blkid  /dev/sdb7 #得到分区的uuid.


/dev/sdb7: LABEL="Entertaiment" UUID="1B10038D4BDFC08D" TYPE="ntfs" PARTUUID="ca77db74-07"

etc/fstab下这样配置

UUID=1B10038D4BDFC08D /mnt ntfs defaults 0 2

其中第一列为UUID, 第二列为挂载目录（该目录必须为空目录），第三列为文件系统类型，第四列为参数，第五列0表示不备份，最后一列必须为２或0(除非引导分区为1)

最后 mount -a 即可