BWRAP(1) User Commands BWRAP(1)NAMEbwrap - container setup utility
SYNOPSISbwrap [OPTION...] [COMMAND]
DESCRIPTIONbwrap is a privileged helper for container setup. You are unlikely to
use it directly from the commandline, although that is possible.
It works by creating a new, completely empty, filesystem namespace
where the root is on a tmpfs that is invisible from the host, and which
will be automatically cleaned up when the last process exists. You can
then use commandline options to construct the root filesystem and
process environment for the command to run in the namespace.
By default, bwrap creates a new mount namespace for the sandbox.
Optionally it also sets up new user, ipc, pid, network and uts
namespaces (but note the user namespace is required if bwrap is not
installed setuid root). The application in the sandbox can be made to
run with a different UID and GID.
If needed (e.g. when using a PID namespace) bwrap is running a minimal
pid 1 process in the sandbox that is responsible for reaping zombies.
It also detects when the initial application process (pid 2) dies and
reports its exit status back to the original spawner. The pid 1 process
exits to clean up the sandbox when there are no other processes in the
sandbox left.
OPTIONS
When options are used multiple times, the last option wins, unless
otherwise specified.
General options:
--help
Print help and exit
--version
Print version
--args FD
Parse nul-separated arguments from the given file descriptor. This
option can be used multiple times to parse options from multiple
sources.
Options related to kernel namespaces:
--unshare-user
Create a new user namespace
--unshare-user-try
Create a new user namespace if possible else skip it
--unshare-ipc
Create a new ipc namespace
--unshare-pid
Create a new pid namespace
--unshare-net
Create a new network namespace
--unshare-uts
Create a new uts namespace
--unshare-cgroup
Create a new cgroup namespace
--unshare-cgroup-try
Create a new cgroup namespace if possible else skip it
--unshare-all
Unshare all possible namespaces. Currently equivalent with:
--unshare-user-try --unshare-ipc --unshare-pid --unshare-net
--unshare-uts --unshare-cgroup-try
--uid UID
Use a custom user id in the sandbox (requires --unshare-user)
--gid GID
Use a custom group id in the sandbox (requires --unshare-user)
--hostname HOSTNAME
Use a custom hostname in the sandbox (requires --unshare-uts)
Options about environment setup:
--chdir DIR
Change directory to DIR
--setenv VAR VALUE
Set an environment variable
--unsetenv VAR
Unset an environment variable
Options for monitoring the sandbox from the outside:
--lock-file DEST
Take a lock on DEST while the sandbox is running. This option can
be used multiple times to take locks on multiple files.
--sync-fd FD
Keep this file descriptor open while the sandbox is running
Filesystem related options. These are all operations that modify the
filesystem directly, or mounts stuff in the filesystem. These are
applied in the order they are given as arguments. Any missing parent
directories that are required to create a specified destination are
automatically created as needed.
--bind SRC DEST
Bind mount the host path SRC on DEST
--dev-bind SRC DEST
Bind mount the host path SRC on DEST, allowing device access
--ro-bind SRC DEST
Bind mount the host path SRC readonly on DEST
--remount-ro DEST
Remount the path DEST as readonly. It works only on the specified
mount point, without changing any other mount point under the
specified path
--proc DEST
Mount procfs on DEST
--dev DEST
Mount new devtmpfs on DEST
--tmpfs DEST
Mount new tmpfs on DEST
--mqueue DEST
Mount new mqueue on DEST
--dir DEST
Create a directory at DEST
--file FD DEST
Copy from the file descriptor FD to DEST
--bind-data FD DEST
Copy from the file descriptor FD to a file which is bind-mounted on
DEST
--ro-bind-data FD DEST
Copy from the file descriptor FD to a file which is bind-mounted
readonly on DEST
--symlink SRC DEST
Create a symlink at DEST with target SRC
Lockdown options:
--seccomp FD
Load and use seccomp rules from FD. The rules need to be in the
form of a compiled eBPF program, as generated by
seccomp_export_bpf.
--exec-label LABEL
Exec Label from the sandbox. On an SELinux system you can specify
the SELinux context for the sandbox process(s).
--file-label LABEL
File label for temporary sandbox content. On an SELinux system you
can specify the SELinux context for the sandbox content.
--block-fd FD
Block the sandbox on reading from FD until some data is available.
--userns-block-fd FD
Do not initialize the user namespace but wait on FD until it is
ready. This allow external processes (like newuidmap/newgidmap) to
setup the user namespace before it is used by the sandbox process.
--info-fd FD
Write information in JSON format about the sandbox to FD.
--new-session
Create a new terminal session for the sandbox (calls setsid()).
This disconnects the sandbox from the controlling terminal which
means the sandbox can't for instance inject input into the
terminal.
Note: In a general sandbox, if you don't use --new-session, it is
recommended to use seccomp to disallow the TIOCSTI ioctl, otherwise
the application can feed keyboard input to the terminal.
--die-with-parent
Ensures child process (COMMAND) dies when bwrap's parent dies.
Kills (SIGKILL) all bwrap sandbox processes in sequence from parent
to child including COMMAND process when bwrap or bwrap's parent
dies. See prctl, PR_SET_PDEATHSIG.
--as-pid-1
Do not create a process with PID=1 in the sandbox to reap child
processes.
--cap-add CAP
Add the specified capability when running as privileged user. It
accepts the special value ALL to add all the permitted caps.
--cap-drop CAP
Drop the specified capability when running as privileged user. It
accepts the special value ALL to drop all the caps. By default no
caps are left in the sandboxed process. The --cap-add and
--cap-drop options are processed in the order they are specified on
the command line. Please be careful to the order they are
specified.
ENVIRONMENT
HOME
Used as the cwd in the sandbox if --cwd has not been explicitly
specified and the current cwd is not present inside the sandbox.
The --setenv option can be used to override the value that is used
here.
EXIT STATUS
The bwrap command returns the exit status of the initial application
process (pid 2 in the sandbox).
Project AtomicBWRAP(1)
