Linux设备上的永久或半永久ID

用来唯一地识别机器
1. 网卡MAC
MAC地址本来是永久地保存在网卡的EEPROM里的，通过驱动程序读取出来，该地址放在 Link层用来识别自身。但是驱动程序可以用
自己配置的MAC地址，而不是从网卡芯片读取的
缺点：
1）有些机器上没有网卡
2）通ifconfig命令可以修改地址
命令:

ifconfig eth0
ip link show eth0
cat /sys/class/net/eth0/address

2. 存储芯片ID
/sys/block/mmcblk2/device/cid

Name	Field	Linux attribute*	Description
Manufacturer ID	MID	manfid	Assigned by SD-3C, LLC.
OEM/Application ID	OID	oemid	Identifies the card OEM and/or the card contents. Assigned by SD-3C, LLC.
Product Name	PNM	name	5 characters long (ASCII)
Product Revision	PRV	hwrev, fwrev	Two binary coded decimal (BCD) digits. Each is four bits. The PRV is in the form x.y. The PRV can also be found by using the hwrev and fwrev, where x=hwrev and y=fwrev
Serial Number	PSN	serial	This 32 bit field is intended to be read as an unsigned integer
Manufacture Date Code	MDT	date	Manufacture date is stored in the form yym (offset from 2000)
CRC7 checksum	CRC		7 bit code used for checking errors in the card register

这个比较难修改，除非修改内核

3. 存储分区ID
文件系统分区时生成的ID，可以通过分区程序等进行修改

blkid
fdisk -l /dev/mmcblk2

PTUUID
PARTUUID
UUID

4. 安装系统时生成的machine-id
/var/lib/dbus/machine-id
/etc/machine-id
缺点：非常容易被root权限用户修改

5. 内核随机UUID

/proc/sys/kernel/random/uuid
/proc/sys/kernel/random/boot_id

每次重启会变

6. USB设备的序列号
存在USB设备的EEPROM中
/sys/bus/usb/devices/*/serial

cat  sys/bus/usb/devices/1-4.3/serial

软sim卡