编译ds920+出现这个错误

Mounting /dev/sdb1 to localdiskp1
/dev/sdb2 localdiskp2
Creating tinycore entry
menuentry 'Tiny Core Image Build' {
        savedefault
        set root=(hd0,msdos3)
        echo Loading Linux...
        linux /vmlinuz64 loglevel=3 cde waitusb=5 vga=791
        echo Loading initramfs...
        initrd /corepure64.gz
        echo Booting TinyCore for loader creation
}
Entries in Localdisk bootloader :
=======================================================================
menuentry 'RedPill DS920+ v7.1.0-42661 (USB, Verbose)' {
menuentry 'RedPill DS920+ v7.1.0-42661 (SATA, Verbose)' {
menuentry 'Tiny Core Image Build' {
Caching files for future use
Found /home/tc/redpill-load/cache/ds920p_42661.pat, copying to cache directory : /mnt/sdb3/auxfiles
cp: failed to preserve ownership for '/mnt/sdb3/auxfiles/ds920p_42661.pat': Operation not permitted