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InstantSSH Plugin

This documentation is for to the latest version available in our plugins store. For an oldest documentation, see the file inside the plugin archive.


Plugin allowing to provide full or restricted shell access to your customers.

A customer to which SSH permissions are given can create SSH users and use them to login on the server.

For each customer, you can set the maximum number of allowed SSH users and choose if they can override the default authentication options. The authentication options are those specified in the documentation of the authorized_keys file (see man authorized_keys).

Default authentication options are set as follow:


which in order:

  • Forbids authentication agent forwarding
  • Forbids TCP forwarding
  • Forbids X11 forwarding

You can override default authentication options by editing the default_ssh_auth_options option which is defined in the plugin configuration file. In that file, you can also restrict the list of authentication options that your customers can add by editing the allowed_ssh_auth_options option. You must note that any authentication option appearing in the the default authentication string must also be specified in the allowed_ssh_auth_options option.

Jailed shells

The Jailed shells allow you to provide SSH access to your customers in a restricted environment from which they can theoretically not escape. It's the preferable way to give an SSH access to an un-trusted customer.

Several commands can be added into the jails by simply adding the required application sections to the app_sections configuration option.

The default configuration comes with a set of preselected application sections which allow to setup very restricted jailed shell environments. These environments are setup using busybox which combines tiny versions of many common UNIX utilities into a single small executable.

See the plugin config.php file for further details.


  • i-MSCP >= 1.1.17 (plugin API >= 0.2.13)
  • openSSH server with public key authentication support enabled

Debian / Ubuntu packages

  • busybox
  • libpam-chroot
  • makejail

You can install these packages by executing the following commands:

# aptitude update
# aptitude install busybox libpam-chroot makejail


  1. If a package is not installed on your system, the plugin installer throws an error
  2. If you have any problem with the PAM chroot module read the Troubleshooting section below


  1. Be sure that all required packages as mentioned in the requirements section are installed on your system
  2. Login into the panel as admin and go to the plugin management interface
  3. Upload the plugin archive
  4. Configure the plugin for your needs by editing the plugin configuration file
  5. Install the plugin


  1. Be sure that all required packages as mentioned in the requirements section are installed on your system
  2. Backup your plugins/InstantSSH/config.php configuration file
  3. Login into the panel as admin and go to the plugin management interface
  4. Deactivate the plugin
  5. Upload the plugin archive
  6. Restore your plugins/InstantSSH/config.php configuration file ( compare it with the new version first )
  7. Activate the plugin

Note: Don't forget to read the file.


PAM chroot module

The PAM chroot module shipped with some libpam-chroot package versions (eg. Ubuntu Lucid) doesn't work as expected. For instance, You can see the following logs in the /var/log/auth.log file:

Oct 13 21:04:31 lucid sshd[1509]: PAM unable to dlopen(/lib/security/ /lib/security/ undefined symbol: __stack_chk_fail_local
Oct 13 21:04:31 lucid sshd[1509]: PAM adding faulty module: /lib/security/

You can fix this easily by following this procedure:

# cd /usr/local/src
# mkdir libpam-chroot && cd libpam-chroot
# apt-get install build-essential debhelper libpam0g-dev
# apt-get source libpam-chroot
# cd libpam-chroot*

Edit the Makefile file to replace the line:

CFLAGS=-fPIC -O2 -Wall -Werror -pedantic


CFLAGS=-fPIC -O2 -Wall -Werror -pedantic -fno-stack-protector

Rebuild and reinstall the package as follow:

# dpkg-buildpackage -uc -us
# cd ..
# dpkg -i libpam-chroot*.deb

Plugin usage

The development of this plugin took me a lot of time, especially the Jailbuilder layer which allows to build the jailed shell environments. Thus, I would ask a small contribution for use of this plugin by doing a donation on my paypal account ( ). If you don't understand such asks, or if you do not want donate, just don't use this plugin.


i-MSCP InstantSSH plugin
Copyright (C) 2014 Laurent Declercq <>

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

See LGPL v2.1



/var/www/virtual/ · Last modified: 2014/12/04 15:15 by nuxwin