mirror of
https://github.com/borgbackup/borg.git
synced 2024-12-22 15:57:15 +00:00
76 lines
4.2 KiB
ReStructuredText
76 lines
4.2 KiB
ReStructuredText
.. include:: serve.rst.inc
|
|
|
|
Examples
|
|
~~~~~~~~
|
|
|
|
``borg serve`` has special support for ssh forced commands (see ``authorized_keys``
|
|
example below): if the environment variable SSH_ORIGINAL_COMMAND is set it will
|
|
ignore some options given on the command line and use the values from the
|
|
variable instead. This only applies to a carefully controlled allowlist of safe
|
|
options. This list currently contains:
|
|
|
|
- Options that control the log level and debug topics printed
|
|
such as ``--verbose``, ``--info``, ``--debug``, ``--debug-topic``, etc.
|
|
- ``--lock-wait`` to allow the client to control how long to wait before
|
|
giving up and aborting the operation when another process is holding a lock.
|
|
|
|
Environment variables (such as BORG_XXX) contained in the original
|
|
command sent by the client are *not* interpreted, but ignored. If BORG_XXX environment
|
|
variables should be set on the ``borg serve`` side, then these must be set in system-specific
|
|
locations like ``/etc/environment`` or in the forced command itself (example below).
|
|
|
|
::
|
|
|
|
# Allow an SSH keypair to run only borg, and only have access to /path/to/repo.
|
|
# Use key options to disable unneeded and potentially dangerous SSH functionality.
|
|
# This will help to secure an automated remote backup system.
|
|
$ cat ~/.ssh/authorized_keys
|
|
command="borg serve --restrict-to-path /path/to/repo",restrict ssh-rsa AAAAB3[...]
|
|
|
|
# Set a BORG_XXX environment variable on the "borg serve" side
|
|
$ cat ~/.ssh/authorized_keys
|
|
command="export BORG_XXX=value; borg serve [...]",restrict ssh-rsa [...]
|
|
|
|
.. note::
|
|
The examples above use the ``restrict`` directive. This does automatically
|
|
block potential dangerous ssh features, even when they are added in a future
|
|
update. Thus, this option should be preferred.
|
|
|
|
If you're using openssh-server < 7.2, however, you have to specify explicitly
|
|
the ssh features to restrict and cannot simply use the restrict option as it
|
|
has been introduced in v7.2. We recommend to use
|
|
``no-port-forwarding,no-X11-forwarding,no-pty,no-agent-forwarding,no-user-rc``
|
|
in this case.
|
|
|
|
Details about sshd usage: `sshd(8) <https://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man8/sshd.8>`_
|
|
|
|
.. _ssh_configuration:
|
|
|
|
SSH Configuration
|
|
~~~~~~~~~~~~~~~~~
|
|
``borg serve``'s pipes (``stdin``/``stdout``/``stderr``) are connected to the ``sshd`` process on the server side. In the event that the SSH connection between ``borg serve`` and the client is disconnected or stuck abnormally (for example, due to a network outage), it can take a long time for ``sshd`` to notice the client is disconnected. In the meantime, ``sshd`` continues running, and as a result so does the ``borg serve`` process holding the lock on the repository. This can cause subsequent ``borg`` operations on the remote repository to fail with the error: ``Failed to create/acquire the lock``.
|
|
|
|
In order to avoid this, it is recommended to perform the following additional SSH configuration:
|
|
|
|
Either in the client side's ``~/.ssh/config`` file, or in the client's ``/etc/ssh/ssh_config`` file:
|
|
::
|
|
|
|
Host backupserver
|
|
ServerAliveInterval 10
|
|
ServerAliveCountMax 30
|
|
|
|
Replacing ``backupserver`` with the hostname, FQDN or IP address of the borg server.
|
|
|
|
This will cause the client to send a keepalive to the server every 10 seconds. If 30 consecutive keepalives are sent without a response (a time of 300 seconds), the ssh client process will be terminated, causing the borg process to terminate gracefully.
|
|
|
|
On the server side's ``sshd`` configuration file (typically ``/etc/ssh/sshd_config``):
|
|
::
|
|
|
|
ClientAliveInterval 10
|
|
ClientAliveCountMax 30
|
|
|
|
This will cause the server to send a keep alive to the client every 10 seconds. If 30 consecutive keepalives are sent without a response (a time of 300 seconds), the server's sshd process will be terminated, causing the ``borg serve`` process to terminate gracefully and release the lock on the repository.
|
|
|
|
If you then run borg commands with ``--lock-wait 600``, this gives sufficient time for the borg serve processes to terminate after the SSH connection is torn down after the 300 second wait for the keepalives to fail.
|
|
|
|
You may, of course, modify the timeout values demonstrated above to values that suit your environment and use case.
|