SFTP user can't edit or create files

Solution 1:

To properly chroot an sftponly group member, you need to set this options in /etc/ssh/sshd_config:

Subsystem       sftp    internal-sftp
Match Group sftponly
        ChrootDirectory /srv/chroot/%u
        ForceCommand internal-sftp

It is a requirement that the home directory, and the directories all the way up to the root of the system, of chrooted users must belong to root:root

Given the following values for a user:

$ id user001
uid=1003(user001) gid=1003(user001) groups=1006(sftponly)
$ grep user001 /etc/passwd
user001:x:1003:1003::/input:/sbin/nologin

You need a directory structure like this one:

$ tree /srv/chroot
/srv/chroot
├── user001
│   └── input

Because user001's HOME directory is evaluated after the chroot call, he/she lands in the input directory, where write permissions are valid:

$ ls -lrtd /srv/chroot/user001/input
drwxrwx--- 2 user001 sftponly 4.0K Apr 07 17:55 /srv/chroot/user001/input