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).