TFTP PXE-T00: Permission denied etc

Ergänzung: update-linbofs liefert eine Warnung - scheint aber nicht relevant zu sein (Linbo mit uefi hat Probleme - ich habe BIOS)

# update-linbofs 
Processing linbofs update ...
  100 %         15,2 MiB / 58,4 MiB = 0,260   2,4 MiB/s       0:24             
Ok!
Processing linbofs-np update ...
  100 %         15,2 MiB / 57,5 MiB = 0,263   2,4 MiB/s       0:24             
Ok!
Processing linbofs64 update ...
  100 %         21,3 MiB / 94,4 MiB = 0,225   2,2 MiB/s       0:42             
Ok!
0+0 Datensätze ein
0+0 Datensätze aus
0 Bytes kopiert, 0,000141416 s, 0,0 kB/s
mkfs.fat 4.1 (2017-01-24)
xorriso 1.4.8 : RockRidge filesystem manipulator, libburnia project.

Drive current: -outdev 'stdio:/srv/linbo/linbo.iso'
Media current: stdio file, overwriteable
Media status : is blank
Media summary: 0 sessions, 0 data blocks, 0 data, 19.9g free
Added to ISO image: directory '/'='/var/cache/linuxmuster/linbo/iso'
xorriso : UPDATE : 978 files added in 1 seconds
xorriso : UPDATE : 978 files added in 1 seconds
xorriso : NOTE : Copying to System Area: 432 bytes from file '/usr/lib/ISOLINUX/isohdpfx.bin'
xorriso : WARNING : Boot image load size exceeds 65535 blocks of 512 bytes. Will record 0 in El Torito to extend ESP to end-of-medium.
libisofs: NOTE : Aligned image size to cylinder size by 263 blocks
xorriso : UPDATE :  33.61% done
xorriso : UPDATE : Thank you for being patient. Working since 1 seconds.
xorriso : UPDATE : Thank you for being patient. Working since 2 seconds.
ISO image produced: 115712 sectors
Written to medium : 115712 sectors at LBA 0
Writing to 'stdio:/srv/linbo/linbo.iso' completed successfully.