pvesm: mark pbs storage as stable

[pve-docs.git] / pvecm.adoc

diff --git a/pvecm.adoc b/pvecm.adoc
index ecddd3768ddf5eaab90d040fdb98dcfa627e123b..2fe532e9998f34af3e1104fe4695fd0ed5c2953a 100644 (file)
--- a/pvecm.adoc
+++ b/pvecm.adoc
@@ -27,8 +27,10 @@ endif::manvolnum[]
 The {PVE} cluster manager `pvecm` is a tool to create a group of
 physical servers. Such a group is called a *cluster*. We use the
 http://www.corosync.org[Corosync Cluster Engine] for reliable group
-communication, and such clusters can consist of up to 32 physical nodes
-(probably more, dependent on network latency).
+communication. There's no explicit limit for the number of nodes in a cluster.
+In practice, the actual possible node count may be limited by the host and
+network performance. Currently (2021), there are reports of clusters (using
+high-end enterprise hardware) with over 50 nodes in production.
 
 `pvecm` can be used to create a new cluster, join nodes to a cluster,
 leave the cluster, get status information and do various other cluster
@@ -327,11 +329,11 @@ After powering off the node hp4, we can safely remove it from the cluster.
 
 ----
  hp1# pvecm delnode hp4
+ Killing node 4
 ----
 
-If the operation succeeds no output is returned, just check the node
-list again with `pvecm nodes` or `pvecm status`. You should see
-something like:
+Use `pvecm nodes` or `pvecm status` to check the node list again. It should
+look something like:
 
 ----
 hp1# pvecm status
@@ -869,6 +871,50 @@ pvecm status
 If you see a healthy cluster state, it means that your new link is being used.
 
 
+Role of SSH in {PVE} Clusters
+-----------------------------
+
+{PVE} utilizes SSH tunnels for various features.
+
+* Proxying console/shell sessions (node and guests)
++
+When using the shell for node B while being connected to node A, connects to a
+terminal proxy on node A, which is in turn connected to the login shell on node
+B via a non-interactive SSH tunnel.
+
+* VM and CT memory and local-storage migration in 'secure' mode.
++
+During the migration one or more SSH tunnel(s) are established between the
+source and target nodes, in order to exchange migration information and
+transfer memory and disk contents.
+
+* Storage replication
+
+.Pitfalls due to automatic execution of `.bashrc` and siblings
+[IMPORTANT]
+====
+In case you have a custom `.bashrc`, or similar files that get executed on
+login by the configured shell, `ssh` will automatically run it once the session
+is established successfully. This can cause some unexpected behavior, as those
+commands may be executed with root permissions on any above described
+operation. That can cause possible problematic side-effects!
+
+In order to avoid such complications, it's recommended to add a check in
+`/root/.bashrc` to make sure the session is interactive, and only then run
+`.bashrc` commands.
+
+You can add this snippet at the beginning of your `.bashrc` file:
+
+----
+# Early exit if not running interactively to avoid side-effects!
+case $- in
+    *i*) ;;
+      *) return;;
+esac
+----
+====
+
+
 Corosync External Vote Support
 ------------------------------