Provided by: dchroot_1.6.10-1ubuntu3_amd64 
NAME
dchroot - enter a chroot environment
SYNOPSIS
dchroot [-h|--help | -V|--version | -l|--list | -i|--info | --config | --location]
[--directory=directory] [-d|--preserve-environment] [-q|--quiet | -v|--verbose] [-c
chroot|--chroot=chroot | --all] [COMMAND [ ARG1 [ ARG2 [ ARGn]]]]
DESCRIPTION
dchroot allows the user to run a command or a login shell in a chroot environment. If no command is
specified, a login shell will be started in the user's home directory inside the chroot.
The command is one or more arguments which will be run in the user's default shell using its -c option.
As a result, shell code may be embedded in this argument. If multiple command options are used, they are
concatenated together, separated by spaces. Users should be aware of the shell quoting issues this
presents, and should use schroot if necessary, which does not have any quoting issues.
The directory the command or login shell is run in depends upon the context. See --directory option
below for a complete description.
This version of dchroot is a compatibility wrapper around the schroot(1) program. It is provided for
backward compatibility with the dchroot command-line options, but schroot is recommended for future use.
See the section “Incompatibilities” below for known incompatibilities with older versions of dchroot.
If no chroot is specified, the chroot name or alias ‘default’ will be used as a fallback.
OPTIONS
dchroot accepts the following options:
Basic options
-h, --help
Show help summary.
-a, --all
Select all chroots.
-c, --chroot=chroot
Specify a chroot to use. This option may be used multiple times to specify more than one chroot,
in which case its effect is similar to --all.
-l, --list
List all available chroots.
-i, --info
Print detailed information about the specified chroots. Note that earlier versions of dchroot did
not include this option.
-p, --path
Print location (path) of the specified chroots.
--config
Print configuration of the specified chroots. This is useful for testing that the configuration
in use is the same as the configuration file. Any comments in the original file will be missing.
Note that earlier versions of dchroot did not include this option.
--directory=directory
Change to directory inside the chroot before running the command or login shell. If directory is
not available, dchroot will exit with an error status.
The default behaviour is as follows (all directory paths are inside the chroot). Unless the
--preserve-environment option is used to preserve the environment, the login shell or command will
run in the user's home directory, or / if the home directory is not available. When the
--preserve-environment option is used, it will attempt to use the current working directory, again
falling back to / if it is not accessible. If none of the directories are available, dchroot will
exit with an error status.
-d, --preserve-environment
Preserve the user's environment inside the chroot environment. The default is to use a clean
environment; this option copies the entire user environment and sets it in the session.
-q, --quiet
Print only essential messages.
-v, --verbose
Print all messages. Note that earlier versions of dchroot did not include this option.
-V, --version
Print version information.
Note that earlier versions of dchroot did not provide long options.
INCOMPATIBILITIES
Debian dchroot prior to version 0.99.0
• Log messages are worded and formatted differently.
• su(1) is no longer used to run commands in the chroot; this is done by dchroot internally. This
change may cause subtle differences. If you find an incompatibility, please report it so it may
be corrected.
• dchroot provides a restricted subset of the functionality implemented by schroot, but is still
schroot underneath. Thus dchroot is still subject to schroot security checking, including PAM
authentication and authorisation, and session management, for example, and hence may behave
slightly differently to older dchroot versions in some circumstances.
Debian dchroot prior to version 1.5.1
• This version of dchroot uses schroot.conf to store the configuration for available chroots, rather
than the dchroot.conf file used historically. dchroot supported automatic migration of
dchroot.conf to the schroot.conf keyfile format with its --config option from versions 0.2.2 to
1.5.0; support for the old format is now no longer available.
DSA dchroot
Machines run by the Debian System Administrators for the Debian Project have a dchroot-dsa package which
provides an alternate dchroot implementation.
• All the above incompatibilities apply.
• This version of dchroot has incompatible command-line options, and while some of those options are
supported or have equivalent options by a different name, the -c option is not required to specify
a chroot, and this version of dchroot cannot implement this behaviour in a backward-compatible
manner (because if -c is omitted, the default chroot is used). DSA dchroot uses the first non-
option as the chroot to use, only allowing one chroot to be used at once.
DIRECTORY FALLBACKS
dchroot will select an appropriate directory to use within the chroot based upon whether the --directory
or --preserve-environment options are used. When explicitly specifying a directory, only one directory
will be used for safety and consistency, while for a login shell or command several possibilities may be
tried. Note that due to multiple fallbacks being considered for commands, it is dangerous to run
commands using dchroot; use schroot instead. The following subsections list the fallback sequence for
each case. CWD is the current working directory, DIR is the directory specified with --directory.
Login shell or command
┌────────────────────┬──────────────────────────────────────────┐
│Transition │ │
│(Host → Chroot) │ Comment │
├────────────────────┼──────────────────────────────────────────┤
│CWD → passwd pw_dir │ Normal behaviour (if --directory and │
│ │ --preserve-environment are not used) │
│CWD → / │ If passwd pw_dir is nonexistent │
│FAIL │ If / is nonexistent │
└────────────────────┴──────────────────────────────────────────┘
--preserve-environment used
┌────────────────┬──────────────────────────────────────────┐
│Transition │ │
│(Host → Chroot) │ Comment │
├────────────────┼──────────────────────────────────────────┤
│CWD → CWD │ Normal behaviour (if │
│ │ --preserve-environment used) │
│CWD → / │ If CWD is nonexistent │
│FAIL │ If / is nonexistent │
└────────────────┴──────────────────────────────────────────┘
--directory used
┌────────────────┬──────────────────────────────────────────┐
│Transition │ │
│(Host → Chroot) │ Comment │
├────────────────┼──────────────────────────────────────────┤
│CWD → DIR │ Normal behaviour │
│FAIL │ If DIR is nonexistent │
└────────────────┴──────────────────────────────────────────┘
No fallbacks should exist under any circumstances.
Debugging
Note that --debug=notice will show the internal fallback list computed for the session.
EXAMPLES
$ dchroot -l↵
Available chroots: sarge [default], sid
$ dchroot -p sid↵
/srv/chroot/sid
$ dchroot -q -c sid -- uname -smr↵
Linux 2.6.16.17 ppc
$ dchroot -q -c sid -- "uname -smr"↵
Linux 2.6.16.17 ppc
$ dchroot -q -c sid "ls -1 / | tac | head -n 4"↵
var
usr
tmp
sys
$ dchroot -c sid↵
I: [sid chroot] Running login shell: “/bin/bash”
$
Use -- to allow options beginning with ‘-’ or ‘--’ in the command to run in the chroot. This prevents
them being interpreted as options for dchroot itself. Note that the top line was echoed to standard
error, and the remaining lines to standard output. This is intentional, so that program output from
commands run in the chroot may be piped and redirected as required; the data will be the same as if the
command was run directly on the host system.
TROUBLESHOOTING
If something is not working, and it's not clear from the error messages what is wrong, try using the
--debug=level option to turn on debugging messages. This gives a great deal more information. Valid
debug levels are ‘none’, and ‘notice’, ‘info’, ‘warning’ and ‘critical’ in order of increasing severity.
The lower the severity level, the more output.
If you are still having trouble, the developers may be contacted on the mailing list:
Debian buildd-tools Developers
<buildd-tools-devel@lists.alioth.debian.org>
BUGS
On the mips and mipsel architectures, Linux kernels up to and including at least version 2.6.17 have
broken personality(2) support, which results in a failure to set the personality. This will be seen as
an “Operation not permitted” (EPERM) error. To work around this problem, set personality to ‘undefined’,
or upgrade to a more recent kernel.
FILES
/etc/schroot/schroot.conf
The system-wide schroot definition file. This file must be owned by the root user, and not be
writable by other.
AUTHORS
Roger Leigh.
This implementation of dchroot uses the same command-line options as the original dchroot by David Kimdon
<dwhedon@debian.org>, but is an independent implementation.
COPYRIGHT
Copyright © 2005-2012 Roger Leigh <rleigh@debian.org>
dchroot is free software: you can redistribute it and/or modify it under the terms of the GNU General
Public License as published by the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
SEE ALSO
schroot(1), sbuild(1), chroot(2), schroot-setup(5), schroot.conf(5).