I recommend to create a dedicated user for that share and specify it in force user(see docs).

Create a user (shareuser for example) and set the owner of everything in the share folder to that user:

adduser --system shareuser
chown -R shareuser /path/to/share

Then add force user and permission mask settings in smb.conf:

[myshare]
path = /path/to/share
writeable = yes
browseable = yes
public = yes
create mask = 0644
directory mask = 0755
force user = shareuser

Note that guest ok is a synonym for public.

At https://manpages.ubuntu.com/manpages/latest/man5/smb.conf.5.html go towards the end of EXPLANATION OF EACH PARAMETER:

   writable

       This parameter is a synonym for writeable.

   writeable (S)

       Inverted synonym for read only.

       Default: writeable = no

Do you have set writeable = yes in your /etc/samba/smb.conf

To allow all users to access and write:

 [share]
 path = /shared
 browseable = yes
 read only = no  
 writeable = yes
 browseable = yes
 public = yes
 create mask = 0644
 directory mask = 0755

Depending on your distro /etc/init.d/samba restart or systemctl restart smb

for what it is worth, I couldn't access my samba share, maybe you have forgotten to add you username to the samba password group (for lack of beter description phrase)

this is what I did to get mine to work

smbpasswd -a username

after by using nautilus, shared my drive/folder with right-click, sharing, etc.

create your password, and use your username and passsword (which you just entered) to access your samba drive, you can also map this drive in Windows

hope this could help

ok.. let's try this..

parent folder (chmod 777 / chown nobody:nogroup -R)

• Folder1 (chmod 770 / chown nobody:group1 -R)

• Folder2 (chmod 770 / chown nobody:group2 -R)

  useradd user1 group1 useradd user2 group2

at samba...

[group1]
guest ok = no (or yes you must check this)
force user = nobody
force group = group1
writelist = user1 @group1
read list = user2 @group2

same for the [group2] but change the order os users at write and read...

bye!

Remove samba by executing following commands

sudo apt-get remove --purge samba
sudo apt-get remove --purge smbclient libsmbclient
sudo apt-get purge samba samba-common
sudo rm -rf /etc/samba/ /etc/default/samba

Install it again

sudo apt-get install samba
sudo apt-get install smbclient libsmbclient

Now original smb.conf has been restored so restart Ubuntu then add user from terminal.

root@Dell-Inspiron-3521:~# sudo smbpasswd -a username (username should be without space eg "sudo smbpasswd -a alamjitsingh")
New SMB password:*********
Retype new SMB password:*********
Added user alamjitsingh.

Now edit smb.conf file as follows. Mentioned lines must be present in the the code.

sudo gedit /usr/share/samba/smb.conf


[global]
 workgroup = WORKGROUP
 passdb backend = tdbsam 
 security = user

[Optional] If you want to share folder which are inside opt directory then you also have to add following line in global section.

usershare owner only = False

In authentication section turn "map to guest = bad user" off by adding # at starting of code

#map to guest = bad user

At last add your personal code

   [sqr_custom]
path = /opt/oracle/psft/pt/ps_home8.55.11/sqr_custom
comment = Personal_Share
read only = no
available = yes
browseable = yes
writable = yes
guest ok = no
public = yes
printable = no
locking = no
strict locking = no

Apart from this your shared folder is in opt folder which require permissions to write. So firstly test this prog by sharing folder of home directory. Then we will proceed further. To know correct path of shared folder drag and drop folder on running terminal.

If you are succeed to run above code then do the following

To create a group:

sudo groupadd demoGroup

To add the user account to the group:

sudo usermod -G demoGroup username(eg alamjitsingh)

For setting permissions of writing

sudo chown -R username:groupname /opt/demo

eg

sudo chown -R alamjitsingh:demogroup /opt/demo

Following lines are for granting the write access to members of the demoGroup in directory demo (It will grant all demoGroup members to write)

sudo chgrp -R demogroup /opt/demo
sudo chmod 2770 /opt/demo

Restart services

sudo service nmbd restart
sudo service smbd restart

eg of shared folder of restricted directory with write privilege

[demo]
path = /opt/demo
comment = HD Share
read only = no
available = yes
browseable = yes
writable = yes
guest ok = no
public = yes
printable = no
locking = no
strict locking = no
force create mode = 0660
force directory mode = 2770
force user = alamjitsingh
force group = demogroup

It looks like your Samba service is setup to use the 'nobody' user account. 'nobody' is one of the default system accounts on UNIX.

So, on your UNIX system, you need to investigate what the permissions are for the '/Windows_Backups/DC' directory and the files within that directory, and make sure that the 'nobody' account can read/write/execute.

On the UNIX system, you will need to use a command called 'man' in order to find out more about 'chmod' and 'chown'.

Proceed with care and take lots of notes about the initial settings and the changes you made (and how you made them), or call in a Linux or UNIX guy/girl.

The solution was to run smbpasswd -a $user for the users in question.

I also changed

create mask = 0660
force directory mode = 02770

to

create mask = 0665
force directory mode = 02775

The problem is the config line:

vfs objects = catia fruit recycle streams_xattr

Note the requirements of the VFS module streams_xattr:

The file system that is shared with this module enabled must support xattrs.

After removing streams_xattr at least writing once worked. However deleting and writing again made problems. Removing fruit alltogether, although using samba only from a mac client, made file operations work as expected.