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 “Migration” below for help migrating an existing
dchroot configuration to schroot. 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. If using the configuration in /etc/dchroot.conf,
the first chroot in the file is the default.
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.
CONFIGURATION
The dchroot configuration file, /etc/dchroot.conf, used by earlier
versions of dchroot, has the following format:
· ‘#’ starts a comment line.
· Blank lines are ignored.
· Chroot definitions are a single line containing an identifier,
path, and an optional personality separated by whitespace.
· The first chroot is also the default chroot.
An example file:
# Example comment
sarge /srv/chroot/sarge
sid /srv/chroot/sid linux32
This file defines a chroot called ‘sarge’, located at
/srv/chroot/sarge, and a second chroot called ‘sid’, located at
/srv/chroot/sid. The second chroot uses the ‘linux32’ personality,
which allows a 32-bit chroot to be used on a 64-bit system. ‘sarge’ is
the default chroot, because it was listed first, which means if the -c
option is omitted this chroot will be used.
INCOMPATIBILITIES
Debian dchroot prior to version 0.99.0
· Log messages are worded and formatted differently.
· The parsing of /etc/dchroot.conf uses a smaller list of allowed
whitespace characters (space and tab), which may cause a parse
error during tokenising if the file contains odd characters as
separators, such as carriage returns, vertical tabs and form
feeds.
· 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.
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.
· This version of dchroot has an incompatible format for
dchroot.conf. While the first two fields are the same, the
remaining fields are an optional users, a list of users
permitted to access the chroot, instead of the personality field
allowed by this version. If access restrictions are needed,
please use /etc/schroot/schroot.conf and add the allowed users
there, as shown in “Migration” below.
MIGRATION
To migrate an existing dchroot configuration to schroot, perform the
following steps:
1 Dump the dchroot configuration in schroot keyfile format to
/etc/schroot/schroot.conf.
# dchroot --config >> /etc/schroot/schroot.conf
2 Edit /etc/schroot/schroot.conf to add access to the users and/or
groups which are to be allowed to access the chroots, and make
any other desired changes to the configuration. See
schroot.conf(5).
3 Remove /etc/dchroot.conf, so that dchroot will subsequently use
/etc/schroot/schroot.conf for its configuration.
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/dchroot.conf
The system-wide dchroot chroot definition file. This file must
be owned by the root user, and not be writable by other. If
present, this file will be used in preference to
/etc/schroot/schroot.conf.
/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. It is
recommended that this file be used in preference to
/etc/dchroot.conf, because the chroots can be used
interchangeably with schroot, and the user and group security
policies provided by schroot are also enforced.
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 © 2005-2010 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).