For what it’s worth, this article https://www.multitech.net/developer/software/corecdp/applications/improving-sd-card-performance/ indicates that there’s an entry in /etc/fstab specifying the sd card, at /media/card, but there is no entry like that in my fstab. Instead, the closest I’ve got is:

tmpfs /run tmpfs mode=0755,noexec,nodev,nosuid,strictatime 0 0

No change in behavior after following the steps at the above link. Any access attempts to /media/card return “No such file or directory”

fdisk -l:

Disk /dev/mmcblk0: 127.8 GB, 127865454592 bytes
255 heads, 63 sectors/track, 15545 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

        Device Boot      Start         End      Blocks  Id System
/dev/mmcblk0p1               3       15546   124852224   7 HPFS/NTFS

• This reply was modified 4 years, 4 months ago by wkhatch@unimar.com.

So, the card was formatted using sdformatter, as HPFS/NTFS so that’s likely part of the problem. I’ll try it on a different machine using a different utility. I think the device should include formatting utilities so you can manage all this directly on the device. Thanks for the clarity on supported fs types; appreciate it.

ext3/4 were no go’s, but FAT32 works, assuming you’re only accessing as root; everybody else outside of root:disk will have no access, which implies you have to run the apps as root; also not really great, but I’ll take it at this point. There’s probably something to be done to change it’s default permissions, umask, etc to at least allow read and execute for world, so I could assign directory level permissions as appropriate, but not going to dig into that right now.

I worked around this by making sure the user my app runs as is also associated with the disk group, so it picks up the right permissions. And yeah, fat32 fs ignore linux permissions aside from whatever they’re initially assigned, so chmod, etc will have no effect; I haven’t found any way of changing them yet.