ChrootX

Small toolbox to create, clone, delete, start and stop chrooted environments, allowing lightweight virtualization within virtual servers again, where LXC or Qemu/KVM might fail to run.

Version: 0.0.7

License: GPLv3

Platforms: Linux (Debian / Ubuntu 14.04 or later)

Chrooted Distributions: Debian, Ubuntu, Fedora, RedHat, CentOS, OpenSUSE, Busybox, Bash (default)

Installation

% git clone http://github.com/Spiritdude/ChrootX

% cd ChrootX

% sudo make requirements install

Usage

All chroot environments are identified with an id:

% sudo chrootx create ch01

% sudo chrootx create ch02 bash

% sudo chrootx start ch01

% sudo chrootx 
   ch01 (minimal): running: 1 process
      ch02 (bash): stopped

% sudo chrootx -l
   ch01:
        status: running
     processes: 2
          type: minimal
         ctime: 2014/11/30 18:23:51.000 (1day 21hrs 34mins 47secs ago)
          size: 3,973,120 bytes
        
   ch02:
        status: stopped
          type: bash
         ctime: 2014/11/30 18:24:58.000 (1day 21hrs 35mins 48secs ago)
          size: 3,969,024 bytes

% sudo chrootx stop ch01

% sudo chrootx new ch03 ubuntu

% sudo chrootx start ch03 /bin/bash
(configure system, and install apache2)

% sudo chrootx start ch03 /etc/init.d/apache2 start

% sudo chrootx help
chrootx 0.0.7 usage: [<options>] <command> [<arguments>]
   options:
      -verbose or -v or -vv   increase verbosity
      -conf <file>            consider configuration file
      -version or --version   display version
      -l                      long output
      -i                      image-based root 
      --format=<type>         image format (default: qcow2)
                                 type: 'cloop', 'cow', 'qcow', 'qcow2', 'raw', 'vdi', 'vmdk'
      --size=<size>           size of image (default: 4G)
                                 e.g. '200M', '2G' etc
      --fs=<type>             fs-type in the image (default: ext4)
      '--comment=a text'      add a timestamped comment, use 'info' as command
      -j                      consider /usr/sbin/jchroot if it exists (default: chroot)
      
   commands:
      create <id> [<type>]    aka 'new', 'install', (default type: 'minimal')
                                 type: 'bash', 'busybox', 'centos', 'debian', 'fedora', 
                                       'minimal', 'nano', 'opensuse', 'redhat', 'ubuntu'
      clone <src> <dst>       clone existing chroot, same as 'new <src> clone:<dst>'
      delete <id>             aka 'deinstall', 'remove', 'destroy'
      start <id> [<cmds>] ..  aka 'run'
      stop <id>               aka 'halt', 'kill', 'abort'
      info <id>               aka 'status'
      list                    default action, use -l to list details

   examples:
      sudo chrootx new sys01 
      sudo chrootx new sys02 ubuntu
      sudo chrootx -i new sys03 clone:sys02
      sudo chrootx -i --size=60G new sys04 clone:sys02
      sudo chrootx clone sys03 sys05

Limitations

• no process isolation, root in chrooted enviroment affects host environment, e.g. chrooted sshd thinks it's running already etc.
• don't run /sbin/init, as it won't able to distinct of chrooted system and host
• hostname can't be set within the chrooted environment, it will change hostname of host

Simple Examples

I recommend following convention for single IP host: enumerate all your chrooted environments, e.g. with 'sys' + number, and use port range of 1000, e.g. sys01 uses 1000-1999 (ssh 1022, httpd 1080), sys02 uses 2000-2999 (ssh 1022, httpd 2080) and so forth.

Lighttpd

% sudo chroot start sys01 /bin/bash

sys01% apt-get install lighttpd tcsh
(install of lighttpd fails likely)

sys01% vi /etc/lighttpd/lighttpd.conf
(change port number, e.g. to 1080)

sys01% apt-get --reinstall install lighttpd
(install succeeds)

SSHD

sys01% apt-get install openssh-server
(fails to start, as it thinks it runs already (on host))

sys01% vi /etc/ssh/sshd_config
(assign new port, e.g. 1022)

sys01% `which sshd`
(launches sshd server manually, as /etc/init.d/ssh start won't do it, 
 as it determines it runs already (on host))

As you see, chrooted environments are rather lame VM approaches, nowhere as nice as LXC or Qemu-KVM.

JChroot

ChrootX supports jchroot, which isolates the processes further, and allows to set hostname with the chroot - check if your vserver permits to run it:

% cd ChrootX
% sudo make jchroot

which compiles and installs jchroot to /usr/sbin/

% sudo chrootx -j start sys01

and see if it works. The -j switch enables jchroot if it exists.

Note: all started chrooted environments must be stopped again before you can restart with -j switch.

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