Samba write issues with Mac OSX and Windows 7

Well ownership and mounted read only is two different pairs of shoes.
So first post the output of

mount
ls -lah /media/

Then we can decide further

osmc@osmc1:~$ mount
devtmpfs on /dev type devtmpfs (rw,relatime,size=369672k,nr_inodes=92418,mode=755)
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,relatime)
tmpfs on /run type tmpfs (rw,relatime)
/dev/mmcblk0p7 on / type ext4 (rw,noatime,stripe=1024,data=ordered)
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 /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
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)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/net_cls type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=23,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
mqueue on /dev/mqueue type mqueue (rw,relatime)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/mmcblk0p6 on /boot type vfat (rw,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,errors=remount-ro)
/dev/mmcblk0p1 on /media/RECOVERY type vfat (rw,nosuid,nodev,relatime,uid=1000,gid=1000,fmask=0111,dmask=0000,allow_utime=0022,codepage=437,iocharset=ascii,shortname=mixed,showexec,utf8,errors=remount-ro,uhelper=udisks)
/dev/mmcblk0p5 on /media/SETTINGS type ext4 (rw,nosuid,nodev,relatime,data=ordered,uhelper=udisks)
/dev/sda1 on /media/EFI type vfat (rw,nosuid,nodev,relatime,uid=1000,gid=1000,fmask=0111,dmask=0000,allow_utime=0022,codepage=437,iocharset=ascii,shortname=mixed,showexec,utf8,errors=remount-ro,uhelper=udisks)
/dev/sda2 on /media/ExtFS4-1 type ext4 (rw,nosuid,nodev,relatime,data=ordered,uhelper=udisks)
/dev/sda3 on /media/Boot OS X type hfsplus (ro,nosuid,nodev,relatime,umask=22,uid=0,gid=0,nls=utf8,uhelper=udisks)
tmpfs on /run/user/1000 type tmpfs (rw,nosuid,nodev,relatime,size=74960k,mode=700,uid=1000,gid=1000)
osmc@osmc1:~$ ls -lah /media/

Ok so obviously it is as expected mounted read/write

Are you saying that command didn’t had an output?

Ran it again, got this:
osmc@osmc1:~$ ls -lah /media/ls -lah /media/
ls: cannot access /media/ls: No such file or directory
/media/:
total 50K
drwxr-xr-x 7 root root 4.0K Sep 11 10:48 .
drwxr-xr-x 23 root root 4.0K Mar 1 2017 …
drwxr-xr-x 1 root root 6 Apr 8 2011 Boot OS X
drwxrwxrwx 2 osmc osmc 512 Dec 31 1969 EFI
drwxrwxrwx 6 root root 4.0K Sep 11 11:00 ExtFS4-1
-rw-r–r-- 1 root root 232 Feb 29 2016 README
drwxrwxrwx 7 osmc osmc 32K Dec 31 1969 RECOVERY
drwxrwxrwx 5 root root 1.0K Mar 1 2017 SETTINGS

First show ls -lah /media/ExtFS4-1/
Secondly have you tried if you can write a file?
touch /media/ExtFS4-1/test

osmc@osmc1:~$ touch /media/ExtFS4-1/test
osmc@osmc1:~$ sudo ls /media/ExtFS4-1/test
/media/ExtFS4-1/test
osmc@osmc1:~$ cd /media/ExtFS4-1
osmc@osmc1:/media/ExtFS4-1$ ls
lost+found Movies test
osmc@osmc1:/media/ExtFS4-1$

So writing as User OSMC works. So whats the problem? You can not write from your MAC via samba when logged in as user osmc?

That’s the problem. Finder changes pointer from arrow to the “No Symbol” (circle with line through it) (/).

Results of LS:
osmc@osmc1:/media/ExtFS4-1$ ls -lah /media/ExtFS4-1/
total 52K
drwxrwxrwx 6 root root 4.0K Sep 11 11:37 .
drwxr-xr-x 7 root root 4.0K Sep 11 10:48 …
-rwxr–r-- 1 osmc osmc 4.0K Sep 11 11:00 ..DS_Store
-rwxr–r-- 1 osmc osmc 6.1K Sep 11 11:00 .DS_Store
drwx------ 2 root root 4.0K Sep 8 15:32 .fseventsd
drwx------ 2 root root 16K Sep 8 15:21 lost+found
drwxr-xr-x 3 501 dialout 4.0K Sep 8 15:30 Movies
-rw-r–r-- 1 osmc osmc 0 Sep 11 11:37 test
d-wx-wx-wx 2 root root 4.0K Sep 8 15:22 .Trashes
–w--w–w- 1 root root 4.0K Sep 8 15:22 .
.Trashes

Clear sign that the MAC can write to it.

This folder has clearly wrong user/group. Did you write it via samba or copied it when the drive was connected to the Mac?

Connect to Mac, I think. Didn’t know about Samba Formating. I can try reformatting attached to Pi with SAMBA from the OSMC interface (more new territory to explore!) or should that happen at the CLI?

Nobody is talking about formatting!
I was asking if you copied the Movies folder when the drive was physically connected to the Mac or via the network/samba.

When you copy files from the Mac not via samba but when the drive is directly connected to the Mac then you would need to change the user afterwards when connected to OSMC.
If you want you can now run once chmod -R osmc:osmc /media/ExtFS4-1/ to fix this.
When you only copy files via samba this problem should not occur

osmc@osmc1:/media/ExtFS4-1$ chmod -R osmc:osmc /media/ExtFS4-1/
chmod: invalid mode: ‘osmc:osmc’
Try ‘chmod --help’ for more information.
osmc@osmc1:/media/ExtFS4-1$ sudo chmod -R osmc:osmc /media/ExtFS4-1/
chmod: invalid mode: ‘osmc:osmc’
Try ‘chmod --help’ for more information.
osmc@osmc1:/media/ExtFS4-1$

FINALLY!!!
Got it with:
osmc@osmc1:/media/ExtFS4-1$ sudo chown osmc /media/ExtFS4-1
osmc@osmc1:/media/ExtFS4-1$ sudo chmod 777 /media/ExtFS4-1 -R

Thanks a TON for all your help!!!

Ups, clearly typo on my side but you luckily already found the correct command chown.

777 should not be necessary 770 should do the job