How to give permission of a folder to a specific user in LINUX/UNIX

It sounds like you want your müşteriler to have file transfer access to a folder without actually giving them shells. This is a good thing because as binfalse pointed out, giving people shells with limited access is tricky because shells need to access all kinds of things scattered on the system just to run.

In order to give SFTP access to a specific folder, you can do something like this.

1. Add a new group to the system, say 'sftponly'.
2. Add any users on your system that should have restricted rights to this group. You could also give them restricted shells like /bin/true, but it's not required.
3. Change your ssh config file (Usually /etc/ssh/sshd_config) with these lines

    Subsystem sftp internal-sftp

    Match Group sftponly
        ChrootDirectory %h
        AllowTCPForwarding no
        X11Forwarding no
        ForceCommand internal-sftp

This would activate the sftp subsystem inside of SSH and force members of that system group to use only that system when logging in. It would also chroot them to their home directories. You could change that to be a sub-folder of their home-directores as well with something like ChrootDirectory %h/musteri_sftp so that they couldn't se the rest of their system files but would login directly to a special subfolder of their home folder.

Kolay gelsin.

This is normal behavior - mount doesn't give write permissions at all. The write permissions are controlled by the permissions bits on the directory in the filesystem (i.e. after it's mounted). To manage who can read and write from/to this filesystem, just use the normal chown and chmod tools.