The FAT file system has no support for ownership. So what Linux does is it simulated the owner and group fields of the file by passing uid=1000,gid=1000
to mount which says: "Every file and directory is owned by 1000 and group 1000."
To find out what these IDs mean, use getent
:
getent passwd 1000
gives you the owner (user) and
getent group 1000
gives you the group.
To fix the error, use
sudo mount -o uid=1000,gid=1000 /dev/sdc1 /mnt/boot
but the other options work around other, important issues with FAT and Linux so a better solution is to take all of them and mount via a script.
#!/bin/bash
options="rw,nosuid,nodev,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf8=1,showexec,flush,uhelper=udisks2"
mount -o "$options" /dev/sdc1 /mnt/boot
and invoke the script with sudo
.