Filesystem has been set read-only problem.

case:

　　when system is running well ,sudden tf became read-only;

analyze:

　　read the kernel log using dmesg , find follow log:

FAT-fs (mmcblk0p1): error, clusters badly computed (59 != 58)
FAT-fs (mmcblk0p1): Filesystem has been set read-only

　 what happen:

　　　　when we writing to tf card ,    tf card have  bad clusters ,  so filesystem  been set read-only.

solution:

　　umout tf card , the remount tf card, that can solution.

when we can't write to tf card , we can find the problem,

　　　　 first ： judge the file system is writabe from /proc/mount

　　 　　second : maybe tf card none free space. thought : df  -h