Create a user and restrict him to his home dir (sftp)

sh

sudo groupadd sftpusers
sudo adduser importer
sudo chown root:root /home/importer
sudo usermod importer -g sftpusers
sudo mkdir /home/importer/data
sudo chown -R importer:sftpusers /home/importer/data

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sftp access configuration
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PasswordAuthentication yes
#Subsystem sftp /usr/lib/openssh/sftp-server
Subsystem sftp internal-sftp
Match Group sftpusers
    ChrootDirectory %h
    ForceCommand internal-sftp
    PermitTunnel no
    AllowAgentForwarding no
    AllowTcpForwarding no
    X11Forwarding no
    
sudo service ssh restart

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mount folder (optional)
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mount --bind /home/importer/data /path/data