So ich habe jetzt noch mal
sudo chmod -vR 755 /datastore
ausgeführt. Danach kann ich auf alle Bilder zugreifen über den Raspberry pi.
Hier die Ausgabe von mount:
[ralf@archbox ~]$ mount
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
sys on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
dev on /dev type devtmpfs (rw,nosuid,relatime,size=8169840k,nr_inodes=2042460,mode=755)
run on /run type tmpfs (rw,nosuid,nodev,relatime,mode=755)
efivarfs on /sys/firmware/efi/efivars type efivarfs (rw,nosuid,nodev,noexec,relatime)
/dev/sda2 on / type btrfs (rw,noatime,compress=lzo,ssd,space_cache,subvolid=666,subvol=/@snapshots/TESTING)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,size=4096k,nr_inodes=1024,mode=755)
cgroup2 on /sys/fs/cgroup/unified type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
none on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=29,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=2305)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,nosuid,nodev,noexec,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,relatime)
tracefs on /sys/kernel/tracing type tracefs (rw,nosuid,nodev,noexec,relatime)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,nosuid,nodev,noexec,relatime)
configfs on /sys/kernel/config type configfs (rw,nosuid,nodev,noexec,relatime)
nfsd on /proc/fs/nfsd type nfsd (rw,relatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,size=8178264k,nr_inodes=409600)
/dev/sda2 on /.snapshots type btrfs (rw,noatime,compress=lzo,ssd,space_cache,subvolid=260,subvol=/@snapshots)
/dev/sda2 on /btrfs type btrfs (rw,noatime,compress=lzo,ssd,space_cache,subvolid=5,subvol=/)
/dev/sda2 on /home type btrfs (rw,noatime,compress=lzo,ssd,space_cache,subvolid=258,subvol=/@home)
systemd-1 on /home/ralf/GMX-Drive type autofs (rw,relatime,fd=57,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=19520)
tmpfs on /home/ralf/.cache type tmpfs (rw,nosuid,nodev,noatime,size=1048576k)
/dev/sda2 on /var/cache/pacman/pkg type btrfs (rw,noatime,compress=lzo,ssd,space_cache,subvolid=259,subvol=/@pkg)
/dev/sda2 on /home/.home_snapshots type btrfs (rw,noatime,compress=lzo,ssd,space_cache,subvolid=293,subvol=/@home_snapshots)
/dev/sdb2 on /cloud type btrfs (rw,noatime,compress=lzo,space_cache,subvolid=5,subvol=/)
/dev/sda1 on /boot type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro)
/dev/sdb3 on /datastore type btrfs (rw,noatime,compress=lzo,space_cache,subvolid=5,subvol=/)
/dev/sdb1 on /backup type btrfs (rw,noatime,compress=lzo,space_cache,subvolid=5,subvol=/)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw,relatime)
fusectl on /sys/fs/fuse/connections type fusectl (rw,nosuid,nodev,noexec,relatime)
tmpfs on /run/user/1000 type tmpfs (rw,nosuid,nodev,relatime,size=1635652k,nr_inodes=408913,mode=700,uid=1000,gid=989)
gvfsd-fuse on /run/user/1000/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,relatime,user_id=1000,group_id=989)
https://mediacenter.gmx.net on /home/ralf/GMX-Drive type fuse (rw,nosuid,nodev,noexec,relatime,user_id=1000,group_id=0,allow_other,max_read=16384,uid=1000,gid=0,helper=davfs)
Unterverzeichnisse habe ich nicht gemountet, lediglich /datastore über /dev/sdb3 in der /etc/fstab