mac下制作U启动盘

1.查询分区

bogon:Downloads lj$ df -hP
Filesystem    512-blocks       Used  Available Capacity  Mounted on
/dev/disk1     234573824   57011376  177050448    25%    /
devfs                371        371          0   100%    /dev
map -hosts             0          0          0   100%    /net
map auto_home          0          0          0   100%    /home
/dev/disk2s1  3906961400 1423011000 2483950400    37%    /Volumes/Elements
/dev/disk3s1    15370904       2136   15368768     1%    /Volumes/U

 2.把USB unmount

bogon:Downloads lj$ diskutil unmountDisk /dev/disk3s1

 3.. 把系统iso复制到u盘

bogon:Downloads lijie$ sudo dd if=ARMMUIx3.iso of=/dev/disk3 
1150560+0 records in
1150560+0 records out
589086720 bytes transferred in 417.868333 secs (1409742 bytes/sec)

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快速几步：

1.把iso转成dmg格式

Shell代码  

1. hdiutil convert -format UDRW -o ~/path/to/target.img ~/path/to/kubuntu.iso  

2. 查找USB有设备盘符

Shell代码  

1. diskutil list  

3. 把USB unmount

Shell代码  

1. diskutil unmountDisk /dev/diskN  
2.   
3. N是查找到u盘 可能是1，2这样的数字  

4. 把dmg复制到u盘

Shell代码  

1. sudo dd if=/path/to/downloaded.img of=/dev/rdiskN bs=1m  

If you see the error dd: Invalid number `1m', you are using GNU dd. Use the same command but replace bs=1m with bs=1M. If you see the error  dd: /dev/diskN: Resource busy  make sure the disk is not in use. Start the "Disk Utility.app" and unmount (not eject) the drive. 

5. 弹出U盘

Shell代码  

1. diskutil eject /dev/diskN  

6. 重启时按住Option键，选择usb启动。