1.配置ubi and ubifs
in .config
注意：如果配置成模块(=m)，则可以手动加载
2.manual attach/detach ubi to mtd
3.manual create ubi volume
4.mount ubifs volume
5.ubi node and ubi_ctrl node
#cat /sys/class/misc/ubi_ctrl/dev
10:63
加入/dev下没有ubi_ctrl,则我们可以sudo mknod ubi_ctrl c 10 63创建一个端点
#./ubiattach /dev/ubi_ctrl -m 6
#cat /sys/class/ubi/ubi0/dev
252:0
当我们attach ubi0 to mtd6后，如果/dev下没有ubi0,则创建一个，sudo mknod ubi0 c 252 0
6.我们可以手动create volume,然后手动mount ubifs,也可以在PC上创建ubi.img（创建好volume,volume写有数据)烧录进mtd device
How to generate ubi image and write to mtd device
注意：在PC上ubuntu使用mkfs.ubifs and ubinize,则我们要用普通的gcc来编译它们，同时在ubuntu上装上lzo库：sudo apt-get install liblzo2-dev
附录：
1).ubinize.cfg
[ubifs]
mode=ubi
image=ubifs.img
vol_id=0
vol_size=500MiB
vol_type=dynamic
vol_name=ubifs0
vol_flags=autoresize
这样这样当./ubiattach /dev/ubi_ctrl -m n后，就可以mount -t ubifs ubi0:ubifs0 /tmp
2)如果是想mount crafms image,只要
./ubinize -o ubi.img -m 4096 -p 512KiB
./ubiformat -q /dev/mtd5 -f ubi.img
ubinize.cfg
[ubifs]
mode=ubi
image=cramfs.img
vol_id=0
vol_size=500MiB
vol_type=dynamic
vol_name=cramfs
vol_flags=autoresize
这样当./ubiattach /dev/ubi_ctrl -m n后就可以从cat /proc/mtd中看到一个ubi volume仿真的mtd device,我们只要mount这个mtd设备对应的mtdblock就可以了（如mount -t cramfs /dev/mtdblock10 /tmp),注意，既然是烧录了cramfs到ubi volume，则我们只能以cramfs方式mount这个volume,不能再以ubifs方式（mount -t ubifs ubi0:cramfs /tmp）mount这个volume.但如果我们用./ubiupdate /dev/ubi0_0 -t wipe out擦干净这个volume后，我们是可以用ubifs方式mount这个volume,但mount起来这个volume，进入mount的目录，是什么内容也没有的。
3)三个volume的ubinize.cfg（注意[]中名字不能一样，vol_id不能一样，vol_name不能一样，另vol_flags=auto_resize只能使用在一个volume上）
[ubifs1]
mode=ubi
image=ubifs.img
vol_id=0
vol_size=20MiB
vol_type=dynamic
vol_name=ubifs0
vol_alignment=1
[cramfs1]
mode=ubi
image=smallroot.cramfs
vol_id=1
vol_size=20MiB
vol_type=dynamic
vol_name=cramfs
vol_alignment=1
[cramfs2]
mode=ubi
image=qtroot.cramfs
vol_id=2
vol_size=50MiB
vol_type=dynamic
vol_name=cramfs2
vol_alignment=1
vol_flags=autoresize
这样当使用./ubiformat写入ubi.img后，则./ubiattach后，我们可以知道多了三个假的mtd device.
第一个可以用mount -t ubifs ubi0:ubifs0 /tmp/ubifs1
第二个可以用mount -t cramfs /dev/mtdblockn /tmp/cramfs1
第二个可以用mount -t cramfs /dev/mtdblockm /tmp/cramfs2
7. How to disable compression?
UBIFS compression may be disabled for whole file system during the image creation time using the "-x none" mkfs.ubifs option. However, if UBIFS compression is enabled, it may be disabled for individual files by cleaning the inode compression flag:
$ chattr -c /mnt/ubifs/file
in shell, or
ioctl(fd, FS_IOC_GETFLAGS, &flags);
flags &= ~FS_COMPR_FL;
ioctl(fd, FS_IOC_SETFLAGS, &flags);
in C programs. Similarly, if compression is disabled by default, you may enable if for individual inodes by setting the compression flag. Note, the code which uses the compression flag works fine on other Linux file-systems, because the flag is just ignored in this case.
It might be a good idea to disable compression for say, mp3 or jpeg files which would anyway not compress and UBIFS would just waste CPU time trying to compress them. The compression may also be disabled if one wants faster file I/O, because UBIFS would not need to compress or decompress the data on reads and write. However, I/O speed may actually become slower if compression is disabled. Indeed, in case of a very fast CPU and very slow flash compressed writes are faster, but this is usually not true for embedded systems.
8.mount cramfs on ubi volume
# cat /proc/mtd
dev:
mtd0: 180000 00080000 "Bootloader"
mtd1: 400000 00080000 "Kernel 0"
mtd2: 400000 00080000 "Kernel 1"
mtd3: 80000 00080000 "Boot up screen"
mtd4: a00000 00080000 "Rescue file system"
mtd5: 1400000 00080000 "Root file system"
mtd6: 3e800000 00080000 "Data area1"
mtd7: 3e800000 00080000 "Data area2"
mtd8: 6a400000 00080000 "Data area3"
mtd9: 16380000 00080000 "reserve"
#./ubiattach /dev/ubi_ctrl -m 6
#./ubimkvol /dev/ubi0 -s 300MiB -N ubifs1
# cat /proc/mtd
dev:
mtd0: 180000 00080000 "Bootloader"
mtd1: 400000 00080000 "Kernel 0"
mtd2: 400000 00080000 "Kernel 1"
mtd3: 80000 00080000 "Boot up screen"
mtd4: a00000 00080000 "Rescue file system"
mtd5: 1400000 00080000 "Root file system"
mtd6: 3e800000 00080000 "Data area1"
mtd7: 3e800000 00080000 "Data area2"
mtd8: 6a400000 00080000 "Data area3"
mtd9: 16380000 00080000 "reserve"
mtd10: 12c3c000 0007e000 "ubifs1"
# cp cramfs.img /dev/mtdblock10
# mount -t cramfs /dev/mtdblock6 /tmp
After create fake mtd device(ubi volume), mount jffs2
#mount -t jffs2 /dev/mtdblock10 /mnt
9.ubiupdatevol /dev/ubi0_0 -t
10.挂载vfat
1)制作vfat.img（在PC上制作）
$ dd if=/dev/zero of=vfat.img bs=1M count=20
#losetup /dev/loop0 vfat.img
#mkfs.vfat /dev/loop0
注意：这有一个warnning,但不用理会：Loop device does not match a floppy size, using default hd params
#mount -t vfat /dev/loop0 vfat_mount_point
往vfat_mount_point目录写东西，或copy东西到这目录
#umount vfat_mount_point
#losetup -d /dev/loop0
2)用ubinize打包成ubi.img，然后用ubiformat写入mtd devie。方法二是用ubiupdatevol先wipe out volume，然后用ubiupdatevol将vfat.img
写入volume.
但注意：因为emulate mtd device是不支持写操作的，所以我mount -t /dev/mtdblockn，这个mtdblockn是一个ubi volume emuluate的mtd device，
所以mount的vfat只可以读，写是无法保存的。（测试中写是能完成，ls也能看到，但sync后重启unit,重新mount可以看到写的数据是没有保存如vfat的）
11.ubifs(read/write/attach/mount)speed,
Wrtie speed -------------------speed=1.66M/s
# time dd if=/dev/zero of=/tmp/ubifs1/zero100M
100+0 records in
100+0 records out
real
user
sys
real
user
sys
Read speed-----------------------speed=2.27M/s
# time cp ubifs1/zero100M /dev/null;time sync
s3c-nand: 1 bit(s) error detected, corrected successfully
s3c-nand: 1 bit(s) error detected, corrected successfully
s3c-nand: 1 bit(s) error detected, corrected successfully
real
user
sys
real
user
sys
12.配置ubifs as rootfs
in .config:
then if we had wrote root fs ubi image to mtd5, then we can boot up with ubi root fs.
13.遇到的rw filesystem change to read only filesystem
# ./ubiattach /dev/ubi_ctrl -m 6
UBI: attaching mtd6 to ubi0
UBI: physical eraseblock size:
UBI: logical eraseblock size:
UBI: smallest flash I/O unit:
UBI: VID header offset:
UBI: data offset:
PEB 0 is bad
PEB 32 is bad
UBI: attached mtd6 to ubi0
UBI: MTD device name:
UBI: MTD device size:
UBI: number of good PEBs:
UBI: number of bad PEBs:
UBI: max. allowed volumes:
UBI: wear-leveling threshold:
UBI: number of internal volumes: 1
UBI: number of user volumes: