Right way to permanently mount SD card on appliance?

littlebigman · 05-13-2013, 06:15 AM

Hello

Since NAND memory wears out each time a file is written, I added an SD card to an appliance running Debian 6.

I can mount the card just fine manually with "mount /dev/mmcblk0 /mnt/sdcard", but I'd like to make sure editing /etc/fstab is the right way to have Linux mount it automatically at boot time.

Here's the infos:

Code:

# fdisk -l

Disk /dev/mmcblk0: 3957 MB, 3957325824 bytes
61 heads, 60 sectors/track, 2111 cylinders
Units = cylinders of 3660 * 512 = 1873920 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

        Device Boot      Start         End      Blocks   Id  System
/dev/mmcblk0p1               3        2112     3860480    b  W95 FAT32

# mount
ubi0:rootfs on / type ubifs (rw,noatime)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
tmpfs on /var/run type tmpfs (rw,nosuid,size=1M,mode=0755)
tmpfs on /var/lock type tmpfs (rw,noexec,nosuid,nodev,size=1M,mode=1777)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev)
/dev/mmcblk0p1 on /mnt/sdcard type vfat (rw)

# cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    defaults        0       0
ubi0:rootfs  /               ubifs   defaults,noatime,rw                    0 0
tmpfs      /var/run        tmpfs   size=1M,rw,nosuid,mode=0755              0 0
tmpfs      /var/lock       tmpfs   size=1M,rw,noexec,nosuid,nodev,mode=1777 0 0
tmpfs      /tmp            tmpfs   defaults,nosuid,nodev                    0 0

Thank you.

goumba · 05-13-2013, 06:28 AM

I'm guessing you formatted it with ext2/3/4?

Code:

# <file system> <mount point>   <type>  <options>       <dump>  <pass>
/dev/mmcblk0p1    /mnt/sdcard    ext2/3/4  defaults,noatime  0  0

I use noatime in mount options with flash, as it's supposed to avoid an extra write by not updating access times of files. Of course, replace 2/3/4 with the version of extfs you used to format the disk. If not using extfs, replace with the appropriate file system.

John VV · 05-13-2013, 05:33 PM

if the port it is plugged into is never going to change then fstab is just fine

but if the card is removed then you will not be able to boot

a udev rule would solve this
but might be more work than is needed if the card will never be removed