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docs/FAQ: Clean up entries regarding SSH settings
Link to recommended ones
(cherry picked from commit 05837fbeb7)
This commit is contained in:
Martin Richtarsky
parent
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96deffce14
3 changed files with 18 additions and 47 deletions
60
docs/faq.rst
60
docs/faq.rst
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@ -757,31 +757,25 @@ You will also get this error if you try to access a repository that uses the arg
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We recommend upgrading to the latest stable version and trying again. We are sorry. We should have thought abount forward
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compatibility and implemented a more helpful error message.
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Why does Borg extract hang after some time?
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-------------------------------------------
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Why am I seeing idle borg serve processes on the repo server?
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-------------------------------------------------------------
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When I do a ``borg extract``, after a while all activity stops, no cpu usage,
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no downloads.
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Please see the next question.
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This may happen when the SSH connection is stuck on server side. You can
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configure SSH on client side to prevent this by sending keep-alive requests,
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for example in ~/.ssh/config:
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Why does Borg disconnect or hang when backing up to a remote server?
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--------------------------------------------------------------------
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::
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Communication with the remote server (using an ssh: repo URL) happens via an SSH
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connection. This can lead to some issues that would not occur during a local backup:
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Host borg.example.com
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# Client kills connection after 3*30 seconds without server response:
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ServerAliveInterval 30
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ServerAliveCountMax 3
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- Since Borg does not send data all the time, the connection may get closed, leading
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to errors like "connection closed by remote".
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- On the other hand, network issues may lead to a dysfunctional connection
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that is only detected after some time by the server, leading to stale ``borg serve``
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processes and locked repositories.
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You can also do the opposite and configure SSH on server side in
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/etc/ssh/sshd_config, to make the server send keep-alive requests to the client:
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::
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# Server kills connection after 3*30 seconds without client response:
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ClientAliveInterval 30
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ClientAliveCountMax 3
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To fix such problems, please apply these :ref:`SSH settings <ssh_configuration>` so that
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keep-alive requests are sent regularly.
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How can I deal with my very unstable SSH connection?
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----------------------------------------------------
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@ -797,32 +791,6 @@ could try to work around:
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to do any more. Due to the way borg mount works, this might be less efficient
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than borg extract for bigger volumes of data.
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Why do I get "connection closed by remote" after a while?
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---------------------------------------------------------
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When doing a backup to a remote server (using a ssh: repo URL), it sometimes
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stops after a while (some minutes, hours, ... - not immediately) with
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"connection closed by remote" error message. Why?
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That's a good question and we are trying to find a good answer in :issue:`636`.
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Why am I seeing idle borg serve processes on the repo server?
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-------------------------------------------------------------
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Maybe the ssh connection between client and server broke down and that was not
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yet noticed on the server. Try these settings:
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::
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# /etc/ssh/sshd_config on borg repo server - kill connection to client
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# after ClientAliveCountMax * ClientAliveInterval seconds with no response
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ClientAliveInterval 20
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ClientAliveCountMax 3
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If you have multiple borg create ... ; borg create ... commands in a already
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serialized way in a single script, you need to give them ``--lock-wait N`` (with N
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being a bit more than the time the server needs to terminate broken down
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connections and release the lock).
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.. _disable_archive_chunks:
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@ -408,7 +408,8 @@ is installed on the remote host, in which case the following syntax is used::
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$ borg init user@hostname:/path/to/repo
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Note: please see the usage chapter for a full documentation of repo URLs.
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Note: Please see the usage chapter for a full documentation of repo URLs. Also
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see :ref:`ssh_configuration` for recommended settings to avoid disconnects and hangs.
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Remote operations over SSH can be automated with SSH keys. You can restrict the
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use of the SSH keypair by prepending a forced command to the SSH public key in
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@ -44,6 +44,8 @@ locations like ``/etc/environment`` or in the forced command itself (example bel
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Details about sshd usage: `sshd(8) <https://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man8/sshd.8>`_
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.. _ssh_configuration:
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SSH Configuration
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~~~~~~~~~~~~~~~~~
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``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``.
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