为什么MySQL在beaglebone black上将eMMC的内容解压到microSD后无法启动?

Why MySQL can't start after extract the contents of the eMMC to microSD on beaglebone black?

MySQL 在我的 beaglebone 上无法启动。
我在执行以下步骤后遇到了我的问题:
我想把eMMC里面的内容提取出来保存下来再用。
我使用 /opt/scripts/tools/eMMC/beaglebone-black-make-microSD-flasher-from-eMMC.sh 将图像从板载 eMMC 写入 microSD 卡。
(跟随此 link http://elinux.org/BeagleBone_Black_Extracting_eMMC_contents#Sources
我的 microSD 卡 (16Gb)
我收到这个错误

rsync: recv_generator: mkdir "/tmp/rootfs/var/www" failed: No space left on device (28)
*** Skipping any contents from this failed directory ***

sent 11164596708 bytes  received 13752725 bytes  1434501.05 bytes/sec
total size is 13493412445  speedup is 1.21
rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1070) [sender=3.0.9]
writing to [/dev/mmcblk0] failed...
-----------------------------
umount: /dev/mmcblk0p1: not mounted


在那之后,beaglebone 的所有光都亮了。
MySQL 以这个错误开始:

Starting mysql (via systemctl): mysql.serviceJob failed. See system journal and 'systemctl status' for details.
 failed!

看起来磁盘空间有问题吗?

root@beaglebone:~# df -h
Filesystem                                              Size  Used Avail Use% Mounted on
rootfs                                                  3.5G  2.4G  941M  72% /
udev                                                     10M     0   10M   0% /dev
tmpfs                                                   100M  736K   99M   1% /run
/dev/disk/by-uuid/e807980f-6d9d-4efb-a42b-d888af80ba37  3.5G  2.4G  941M  72% /
tmpfs                                                   249M     0  249M   0% /dev/shm
tmpfs                                                   249M     0  249M   0% /sys/fs/cgroup
tmpfs                                                   5.0M     0  5.0M   0% /run/lock
tmpfs                                                   100M     0  100M   0% /run/user
/dev/mmcblk0p1                                           96M   73M   24M  76% /boot/uboot

Tomcat服务器正常启动。

更新:

这是使用 systemd-journalctl -a cmd 时的日志:

Jan 03 06:49:17 beaglebone mysqld[9443]: 170103  6:49:17 [Warning] Using unique option prefix key_buffer instead of key_buffer_size is deprecated and will be removed in
Jan 03 06:49:17 beaglebone mysqld[9443]: /usr/sbin/mysqld: Error on realpath() on '/var/lib/mysql-files' (Error 2)

我的问题是什么?

查看日志后:我认为我的问题是缺少文件夹。
我刚刚创建了新的 '/var/lib/mysql-files'
MySQL 已开始。