mount_msdos: Unsupported sector size (36352)

chris (2015-06-12 13:54:41)
0 replies
Trying to mount an SD card on my mac, I was encountering this error:

knockthrough:Untitled chris$ sudo mount -t msdos  /dev/disk1s1 /Volumes/sdcardmountpoint/
mount_msdos: Unsupported sector size (36352)

That is intensely frustrating and if you google this error (as of today), there are only 3 search results offered - none of which answer the problem. Well anyway, I was trying to mount an SD which I am using for a Raspberry Pi so that I could modify hdmi settings within the config.txt file. Unfortunately I had to trash the image on the card and reformat the card using a block/sector size which my mac would accommodate. Easiest way to do this is as follows:

knockthrough:Untitled chris$ sudo /sbin/newfs_msdos -F 32 -S 1024 /dev/disk1s1
newfs_msdos: warning: /dev/disk1s1 is not a character device
512 bytes per physical sector
/dev/disk1s1: 7742668 sectors in 1935667 FAT32 clusters (4096 bytes/cluster)
bps=1024 spc=4 res=32 nft=2 mid=0xf8 spt=32 hds=255 hid=4096 drv=0x80 bsec=7757824 bspf=7562 rdcl=2 infs=1 bkbs=6
knockthrough:Untitled chris$

This instructs the mac to setup an msdos filesystem on the device at /dev/disk1s1, using the FAT32 format and a sector size of 1024 bytes. To prove that this now mounts, here's the next command:

nockthrough:Untitled chris$ sudo mount -t msdos  /dev/disk1s1 /Volumes/sdcardmountpoint/
knockthrough:Untitled chris$ mount
/dev/disk0s2 on / (hfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
/dev/disk1s1 on /Volumes/sdcardmountpoint (msdos, local, noowners)

and there it is...