SFTP用ユーザを作成

# useradd sftpuser
# passwd sftpuser
Changing password for user sftpuser.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.

SFTP用グループを作成、権限付与

# groupadd sftpgroup
# gpasswd -a sftpuser sftpgroup
# chmod 775 /home/sftpuser/
# chown root:root /home/sftpuser/
# mkdir -p /home/sftpuser/work
# chown sftpuser:sftpgroup /home/sftpuser/work/

SUDO設定

# visudo 
sftpuser ALL=(ALL) ALL

# su sftpuser

SSHログイン用設定

# nano /etc/ssh/sshd_config
最後の方に追加する
Match User sftpuser
  PasswordAuthentication yes
  X11Forwarding no
  AllowTcpForwarding no
  ForceCommand internal-sftp
  ChrootDirectory /home/sftpuser

# service sshd restart

Chrootディレクトリのバインドマウントを実行、永続化

# mount -B /var/www/vhosts/example.com/wp-content/themes/work /home/sftpuser/work

# nano /etc/fstab
/var/www/vhosts/example.com/wp-content/themes/work /home/sftpuser/work bind 0 0
text-decoration: underline;
text-underline-position: under;
text-decoration-color: hsla(240, 100%, 47%, 0.5);
/*
hsl()ではhue:色相、saturation:彩度、lightness:輝度の3要素で色を指定
hsla()で透明度もあわせて指定
*/