schroot-setup man page

schroot-setup — schroot chroot setup scripts

Description

schroot uses scripts to set up and then clean up the chroot environment. The directory /etc/schroot/setup.d contains scripts run when a chroot is created and destroyed.  Several environment variables are set while the scripts are being run, which allows their behaviour to be customised, depending upon, for example, the type of chroot in use.

The scripts are run in name order, like those run by init(8), by using the same style of execution as run-parts(8).

The setup scripts are all invoked with two options:

1

The action to perform.

When a session is first started, the chroot is set up by running the scripts in /etc/schroot/setup.d with the ‘setup-start’ option.  When the session is ended, the scripts in /etc/schroot/setup.d are run in reverse order with the ‘setup-stop’ option.

2

The chroot status.

This is either ‘ok’ if there are no problems, or ‘fail’ if something went wrong.  For example, particular actions may be skipped on failure.

Note that the scripts should be idempotent.  They must be idempotent during the ‘setup-stop’ phase, because they may be run more than once, for example on failure.

Environment

General variables

AUTH_USER

The username of the user the command in the chroot will run as.

CHROOT_NAME

The chroot name.  Note that this is the name of the orignal chroot before session creation; you probably want SESSION_ID.

HOST
HOST_OS
HOST_VENDOR
HOST_CPU

The host system architecture schroot is running upon.  This may be used to introduce architecture-specific behaviour into the setup scripts where required.  HOST is the GNU triplet for the architecture, while HOST_OS, HOST_VENDOR and HOST_CPU are the component parts of the triplet.

LIBEXEC_DIR

The directory under which helper programs are located.

MOUNT_DIR

The directory under which non-filesystem chroots are mounted (e.g. block devices and LVM snapshots).

PID

The process ID of the schroot process.

PLATFORM

The operating system platform schroot is running upon.  This may be used to introduce platform-specific behaviour into the setup scripts where required. Note that the HOST variables are probably what are required.  In the context of schroot, the platform is the supported configuration and behaviour for a given architecture, and may be identical between different architectures.

SESSION_ID

The session identifier.

VERBOSE

Set to ‘quiet’ if only error messages should be printed, ‘normal’ if other messages may be printed as well, and ‘verbose’ if all messages may be printed.  Previously called AUTH_VERBOSITY.

CHROOT_SESSION_CREATE

Set to ‘true’ if a session will be created, otherwise ‘false’.

CHROOT_SESSION_CLONE

Set to ‘true’ if a session will be cloned, otherwise ‘false’.

CHROOT_SESSION_PURGE

Set to ‘true’ if a session will be purged, otherwise ‘false’.

CHROOT_TYPE

The type of the chroot.  This is useful for restricting a setup task to particular types of chroot (e.g. only block devices or LVM snapshots).

CHROOT_NAME

The name of the chroot.  This is useful for restricting a setup task to a particular chroot, or set of chroots.

CHROOT_ALIAS

The name of the alias used to select the chroot.  This is useful for specialising a setup task based upon one of its alternative alias names, or the default chroot name.  For example, it could be used to specify additional sources in /etc/apt/sources.list, such as a stable-security alias for a stable chroot, or an experimental alias for an unstable chroot.

CHROOT_DESCRIPTION

The description of the chroot.

CHROOT_MOUNT_LOCATION

The location to mount the chroot.  It is used for mount point creation and mounting.

CHROOT_LOCATION

The location of the chroot inside the mount point.  This is to allow multiple chroots on a single filesystem.  Set for all mountable chroot types.

CHROOT_PATH

The absolute path to the chroot.  This is typically CHROOT_MOUNT_LOCATION and CHROOT_LOCATION concatenated together.  This is the path which should be used to access the chroots.

Plain and directory chroot variables

These chroot types use only general variables.

File variables

CHROOT_FILE

The file containing the chroot files.

CHROOT_FILE_REPACK

Set to ‘true’ to repack the chroot into an archive file on ending a session, otherwise ‘false’.

Mountable chroot variables

These variables are only set for directly mountable chroot types.

CHROOT_MOUNT_DEVICE

The device to mount containing the chroot. mounting.

CHROOT_MOUNT_OPTIONS

Options to pass to mount(8).

CHROOT_LOCATION

The location of the chroot inside the mount point.  This allows the existence of multiple chroots on a single filesystem.

Filesystem union variables

CHROOT_UNION_TYPE

Union filesystem type.

CHROOT_UNION_MOUNT_OPTIONS

Union filesystem mount options.

CHROOT_UNION_OVERLAY_DIRECTORY

Union filesystem overlay directory (writable).

CHROOT_UNION_UNDERLAY_DIRECTORY

Union filesystem underlay directory (read-only).

Block device variables

CHROOT_DEVICE

The device containing the chroot root filesystem.  This is usually, but not necessarily, the device which will be mounted.  For example, an LVM snapshot this will be the original logical volume.

LVM snapshot variables

CHROOT_LVM_SNAPSHOT_NAME

Snapshot name to pass to lvcreate(8).

CHROOT_LVM_SNAPSHOT_DEVICE

The name of the LVM snapshot device.

CHROOT_LVM_SNAPSHOT_OPTIONS

Options to pass to lvcreate(8).

Custom variables

Custom keys set in schroot.conf will be uppercased and set in the environment as described in schroot.conf(5).

Files

Setup script configuration

The directory /etc/schroot/default contains the default settings used by setup scripts.

config

Main configuration file read by setup scripts.  The format of this file is described in schroot-script-config(5). This is the default value for the script-config key.  Note that this was formerly named /etc/schroot/script-defaults.  The following files are referenced by default:

copyfiles

A list of files to copy into the chroot from the host system.  Note that this was formerly named /etc/schroot/copyfiles-defaults.

fstab

A file in the format decribed in fstab(5), used to mount filesystems inside the chroot.  The mount location is relative to the root of the chroot.  Note that this was formerly named /etc/schroot/mount-defaults.

nssdatabases

System databases (as described in /etc/nsswitch.conf on GNU/Linux systems) to copy into the chroot from the host.  Note that this was formerly named /etc/schroot/nssdatabases-defaults.

Setup scripts

The directory /etc/schroot/setup.d contains the chroot setup scripts.

00check

Print debugging diagnostics and perform basic sanity checking.

05file

Unpack, clean up, and repack file-based chroots.

05fsunion

Create and remove union filesystems.

05lvm

Create and remove LVM snapshots.

10mount

Mount and unmount filesystems.

15binfmt

Sets up the QEMU user emulator using binfmt-support.  This permits a chroot for a different CPU architecture to be used transparently, providing an alternative to cross-compiling or whole-machine emulation.

15killprocs

Kill processes still running inside the chroot when ending a session, which would prevent unmounting of filesystems and cleanup of any other resources.

20copyfiles

Copy files from the host system into the chroot.  Configure networking by copying hosts and resolv.conf, for example.

20nssdatabases

Configure system databases by copying passwd, shadow, group etc. into the chroot.

50chrootname

Set the chroot name (/etc/debian_chroot) in the chroot.  This may be used by the shell prompt to display the current chroot.

Authors

Roger Leigh.

See Also

schroot(1), fstab(5), schroot.conf(5), schroot-script-config(5), run-parts(8).

Referenced By

dchroot(1), schroot(1), schroot.conf(5), schroot-faq(7), schroot-script-config(5).

27 Jan 2013 Version 1.6.5 Debian sbuild