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Jail install HOWTO
Installation quick guide

Published at 26/08/2003 17:10:48
By Juan M. Casillas

Index

  1. Compiling and installing
  2. Creating the chrooted environment
  3. Adding software into the chrooted environment
  4. Adding users into the chrooted environment
  5. Troubleshooting
  6. Porting, improvements and hacks
  7. Copyright

Compiling and installing

Just untar the package, cd to ./src and edit the makefile and do a ?make?. Now you can choose your architecture from Linux, FreeBSD, Solaris and IRIX. then configure the installation directory (default /usr/local) and you?re ready !. Perhaps you need to tune some of the compiler directives, if you are in a different platform than these ones supported by Jail. After a while, you will have the jail binary created. Then, issue a ?make install?, to do this, you have to be root (the default path to install is /usr/local). Now you are ready to play with jail.

Creating the chrooted environment

Now choose where directory will be your chroot environment. In my example, I choose /var/chroot for the chrooted environment. Now become root, and launch the mkjailenv command:

/usr/local/bin/mkjailenv /var/chroot

The output should look like this:

                mkjailenv
                A component of Jail
                http://www.gsyc.inf.uc3m.es/~assman/jail/
                Juan M. Casillas 

                Making chrooted environment into /var/chroot
                        Doing preinstall()
                        Doing special_devices()
                        Doing gen_template_password()
                        Doing postinstall()
                Done.

After that, you will have the basic chrooted environment installed under /var/chroot.

Adding software into the chrooted environment

After the chrooted environment has been created, we have to add some software inside it. To do this, we will use addjailsw. This scripts, if called without -P argument, will install a default set of programs into the chrooted environment. First of all, were are going to install the basic set of programs, an then we will install the less command.

To install the basic set of programs, we will issue the following command:

/usr/local/bin/addjailsw /var/chroot

The output of the program should look like this:


  addjailsw
  A component of Jail
  http://www.gsyc.inf.uc3m.es/~assman/jail/
  Juan M. Casillas 

  Guessing head args()
  Guessing bash args()
  Guessing cat args()
  Guessing pwd args()
  Guessing ln args()
  Guessing mkdir args()
  Guessing rmdir args()
  Guessing ls args()
  Guessing sh args()
  Guessing mv args()
  Guessing rm args()
  Guessing more args()
  Guessing grep args()
  Guessing vi args()
  Guessing id args()
  Guessing cp args()
  Guessing tail args()
  Guessing touch args()
  creating /var/chroot//bin/ln
  creating /var/chroot//etc/nsswitch.conf
  creating /var/chroot//var/tmp/vi.recover/vi.wTrhwB
  creating /var/chroot//etc/group
  Warning: not allowed to overwrite /var/chroot/etc/group
  creating /var/chroot//lib/libncurses.so.5
  creating /var/chroot//bin/ls
  creating /var/chroot//etc/mtab
  creating /var/chroot//bin/mkdir
  creating /var/chroot//bin/rmdir
  creating /var/chroot//bin/bash
  creating /var/chroot//bin/sh
  creating /var/chroot//etc/passwd
  Warning: not allowed to overwrite /var/chroot/etc/passwd
  creating /var/chroot//tmp/vi.UrdLM7
  creating /var/chroot//bin/mv
  creating /var/chroot//etc/ld.so.cache
  creating /var/chroot//etc/terminfo/x/xterm
  creating /var/chroot//bin/rm
  creating /var/chroot//usr/bin/vi
  creating /var/chroot//lib/libdl.so.2
  creating /var/chroot//usr/bin/id
  creating /var/chroot//lib/ld-linux.so.2
  creating /var/chroot//usr/bin/tail
  creating /var/chroot//bin/cp
  creating /var/chroot//lib/libc.so.6
  creating /var/chroot//usr/bin/head
  creating /var/chroot//bin/cat
  creating /var/chroot//lib/libnsl.so.1
  creating /var/chroot//bin/touch
  creating /var/chroot//lib/libnss_compat.so.2
  creating /var/chroot//bin/pwd
  creating /var/chroot//bin/more
  creating /var/chroot//bin/grep
  creating /var/chroot//proc/meminfo
  creating /var/chroot/null:c:1:3
  creating /var/chroot/tty:c:5:0

  Done.

As you can see in the output there are some temporal files, and also, there are some files that are begin overwritten, and other that are not allowed to be overwritted. This files are the passwd, group and shadow files of the chrooted environment. When the scripts ends, it cleans all the temporal directories in the chrooted environment.

Now, we are going to install the ?awk? program into the chrooted environment. We need to call the addjailsw script with the -P argument:

/usr/local/bin/addjailsw /var/chroot -P awk 

The output for the script will be something like this:


  addjailsw
  A component of Jail
  http://www.gsyc.inf.uc3m.es/~assman/jail/
  Juan M. Casillas 

  Guessing awk args(0)
  creating /var/chroot//lib/libc.so.6
  Warning: file /var/chroot/lib/libc.so.6 exists. 
  Overwritting it
  creating /var/chroot//usr/bin/awk
  creating /var/chroot//etc/ld.so.cache
  Warning: file /var/chroot/etc/ld.so.cache exists. 
  Overwritting it
  creating /var/chroot//lib/libm.so.6
  creating /var/chroot//lib/ld-linux.so.2
  Warning: file /var/chroot/lib/ld-linux.so.2 exists. 
  Overwritting it

  Done.

Now, you have awk installed into the chroot environment. You should use this script to install all the software into the chrooted environment

Adding users into the chrooted environment

Now, it is time to add some users into the chroot environment. First of all we need to have the users created in the system, so you can add them by hand, or using adduser. For this example, I will create a new user called chroottest with adduser To do this:

/usr/local/bin/addjailuser /var/chroot /home/chroottest /bin/bash chroottest

After answer all the questions and set the user password, we are ready to add this users to the chrooted environment. This program accepts some parameters:

  1. the first parameter is the full path to the chrooted environment (in my example, is /var/chroot)
  2. the full path of the directory under the user will live. This path will be created under the chrooted environment, and when the user logs into, it will see it as the full path. (e.g, in our example, /home/chroottest is the home directory. addjailuser will create /var/chroot/home/chrootest, and when the user logs into, he will see /home/chroottest. Because it lives under the chrooted environment, he will see a ?virtual? home directory).
  3. The full path to the shell that the user will use. (e.g, I like to use bash, so I use the /bin/bash parameter. NOTE: if you want yo use some other shell (or program) you will need to add it to the list of the installed programs (see section 2 to see how to do that).
  4. The name of the user, in my example, chroottest

After that, we are ready to launch the program (always as root):

   /usr/local/bin/addjailuser 
   /var/chroot 
   /home/chroottest 
   /bin/bash 
   chroottest

The inverted slashes are to allow us insert carriage returns because the line is too long to type it in a single shell line. After launch the command, the output should look like this:

  addjailuser
  A component of Jail
  http://www.gsyc.inf.uc3m.es/~assman/jail/
  Juan M. Casillas 

  Adding user pruebas in  chrooted environment /var/chroot
  Done.

That?s all. You have the user added into the chrooted environment. Now is time to try it:

su - chroottest

As you can see, you are in the new created chrooted environment, Congratulations !

Troubleshooting

Setting up SSH & scp

Now jail support terminal handling and parameter-passing, so configure ssh & scp now is possible. You only have to install a standard chrooted environment (just as described in this section) and then, install the two programs with the addjailsw script. First of all, install ssh:

/usr/local/bin/addjailsw /var/chroot -P ssh --version

To finish, install scp in the same way:

/usr/local/bin/addjailsw /var/chroot -P scp --version

Now you have the two programs installed in the chrooted environment; you can test it doing a ssh form in and out the chrooted environment, and a scp.

Well, there are not troubleshooting section :( Im writting some documentation, and improving the code for jail, mkjailenv, addjailsw and addjailuser. Also we have a mailinglist with some of the tricks and recipes to have jail working:

Jail mail archive

Also, you can generate some log files and send them back to me, so I will try to manage them and find an answer for your problems. I usually need a log for mkenv.pl, addjailuser.pl, addjailsw.pl and the output for a login session into a chrooted account.

Porting, improvements and hacks

If you tailor mkenv.pl for your platform, please send me the new mkenv.pl, so I can put it into the distribution, also, send me patches if you write any of them for jail.

Copyright

This program, the web site, all the documentation an the scripts has been written by Juan M. Casillas . All the source code, web pages, documentation and scripts has been released using the GNU Public License, version 2.0 or above (you can find the complete GPL text in a file called GPL, in the root file of jail?s distribution). Also, this program has been done and improved thanks to the help of lot of people arround the world. Thanks to all for your work, your test-drives, and your improvements & ideas.


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