-Proxmox Cluster file system (pmxcfs)
+[[chapter_pmxcfs]]
+ifdef::manvolnum[]
+pmxcfs(8)
+=========
+:pve-toplevel:
+
+NAME
+----
+
+pmxcfs - Proxmox Cluster File System
+
+SYNOPSIS
+--------
+
+include::pmxcfs.8-synopsis.adoc[]
+
+DESCRIPTION
+-----------
+endif::manvolnum[]
+
+ifndef::manvolnum[]
+Proxmox Cluster File System (pmxcfs)
====================================
+:pve-toplevel:
+endif::manvolnum[]
-The Proxmox Cluster file system (pmxcfs) is a database-driven file
+The Proxmox Cluster file system (``pmxcfs'') is a database-driven file
system for storing configuration files, replicated in real time to all
-cluster nodes using corosync. We use this to store all PVE related
+cluster nodes using `corosync`. We use this to store all PVE related
configuration files.
Although the file system stores all data inside a persistent database
on disk, a copy of the data resides in RAM. That imposes restriction
-on the maximal size, which is currently 30MB. This is still enough to
+on the maximum size, which is currently 30MB. This is still enough to
store the configuration of several thousand virtual machines.
-Advantages
-----------
+This system provides the following advantages:
* seamless replication of all configuration to all nodes in real time
* provides strong consistency checks to avoid duplicate VM IDs
-* read-only when a node looses quorum
+* read-only when a node loses quorum
* automatic updates of the corosync cluster configuration to all nodes
* includes a distributed locking mechanism
+
POSIX Compatibility
-~~~~~~~~~~~~~~~~~~~
+-------------------
The file system is based on FUSE, so the behavior is POSIX like. But
some feature are simply not implemented, because we do not need them:
* `O_TRUNC` creates are not atomic (FUSE restriction)
-File access rights
-~~~~~~~~~~~~~~~~~~
+File Access Rights
+------------------
-All files and directories are owned by user 'root' and have group
-'www-data'. Only root has write permissions, but group 'www-data' can
+All files and directories are owned by user `root` and have group
+`www-data`. Only root has write permissions, but group `www-data` can
read most files. Files below the following paths:
/etc/pve/priv/
are only accessible by root.
+
Technology
----------
We use the http://www.corosync.org[Corosync Cluster Engine] for
cluster communication, and http://www.sqlite.org[SQlite] for the
-database file. The filesystem is implemented in user space using
+database file. The file system is implemented in user space using
http://fuse.sourceforge.net[FUSE].
-File system layout
+File System Layout
------------------
The file system is mounted at:
[width="100%",cols="m,d"]
|=======
-|corosync.conf |corosync cluster configuration file (previous to {pve} 4.x this file was called cluster.conf)
-|storage.cfg |{pve} storage configuration
-|datacenter.cfg |{pve} datacenter wide configuration (keyboard layout, proxy, ...)
-|user.cfg |{pve} access control configuration (users/groups/...)
-|domains.cfg |{pve} Authentication domains
-|authkey.pub | public key used by ticket system
-|pve-root-ca.pem | public certificate of cluster CA
-|priv/shadow.cfg | shadow password file
-|priv/authkey.key | private key used by ticket system
-|priv/pve-root-ca.key | private key of cluster CA
-|nodes/<NAME>/pve-ssl.pem | public ssl certificate for web server (signed by cluster CA)
-|nodes/<NAME>/pve-ssl.key | private ssl key for pve-ssl.pem
-|nodes/<NAME>/pveproxy-ssl.pem | public ssl certificate (chain) for web server (optional override for pve-ssl.pem)
-|nodes/<NAME>/pveproxy-ssl.key | private ssl key for pveproxy-ssl.pem (optional)
-|nodes/<NAME>/qemu-server/<VMID>.conf | VM configuration data for KVM VMs
-|nodes/<NAME>/lxc/<VMID>.conf | VM configuration data for LXC containers
-|firewall/cluster.fw | Firewall config applied to all nodes
-|firewall/<NAME>.fw | Firewall config for individual nodes
-|firewall/<VMID>.fw | Firewall config for VMs and Containers
+|`corosync.conf` | Corosync cluster configuration file (previous to {pve} 4.x this file was called cluster.conf)
+|`storage.cfg` | {pve} storage configuration
+|`datacenter.cfg` | {pve} datacenter wide configuration (keyboard layout, proxy, ...)
+|`user.cfg` | {pve} access control configuration (users/groups/...)
+|`domains.cfg` | {pve} authentication domains
+|`status.cfg` | {pve} external metrics server configuration
+|`authkey.pub` | Public key used by ticket system
+|`pve-root-ca.pem` | Public certificate of cluster CA
+|`priv/shadow.cfg` | Shadow password file
+|`priv/authkey.key` | Private key used by ticket system
+|`priv/pve-root-ca.key` | Private key of cluster CA
+|`nodes/<NAME>/pve-ssl.pem` | Public SSL certificate for web server (signed by cluster CA)
+|`nodes/<NAME>/pve-ssl.key` | Private SSL key for `pve-ssl.pem`
+|`nodes/<NAME>/pveproxy-ssl.pem` | Public SSL certificate (chain) for web server (optional override for `pve-ssl.pem`)
+|`nodes/<NAME>/pveproxy-ssl.key` | Private SSL key for `pveproxy-ssl.pem` (optional)
+|`nodes/<NAME>/qemu-server/<VMID>.conf` | VM configuration data for KVM VMs
+|`nodes/<NAME>/lxc/<VMID>.conf` | VM configuration data for LXC containers
+|`firewall/cluster.fw` | Firewall configuration applied to all nodes
+|`firewall/<NAME>.fw` | Firewall configuration for individual nodes
+|`firewall/<VMID>.fw` | Firewall configuration for VMs and Containers
|=======
+
Symbolic links
~~~~~~~~~~~~~~
[width="100%",cols="m,m"]
|=======
-|local |nodes/<LOCAL_HOST_NAME>
-|qemu-server |nodes/<LOCAL_HOST_NAME>/qemu-server/
-|lxc |nodes/<LOCAL_HOST_NAME>/lxc/
+|`local` | `nodes/<LOCAL_HOST_NAME>`
+|`qemu-server` | `nodes/<LOCAL_HOST_NAME>/qemu-server/`
+|`lxc` | `nodes/<LOCAL_HOST_NAME>/lxc/`
|=======
+
Special status files for debugging (JSON)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[width="100%",cols="m,d"]
|=======
-| .version |file versions (to detect file modifications)
-| .members |Info about cluster members
-| .vmlist |List of all VMs
-| .clusterlog |Cluster log (last 50 entries)
-| .rrd |RRD data (most recent entries)
+|`.version` |File versions (to detect file modifications)
+|`.members` |Info about cluster members
+|`.vmlist` |List of all VMs
+|`.clusterlog` |Cluster log (last 50 entries)
+|`.rrd` |RRD data (most recent entries)
|=======
+
Enable/Disable debugging
~~~~~~~~~~~~~~~~~~~~~~~~
You can enable verbose syslog messages with:
- echo "1" >/etc/pve/.debug
+ echo "1" >/etc/pve/.debug
And disable verbose syslog messages with:
- echo "0" >/etc/pve/.debug
+ echo "0" >/etc/pve/.debug
Recovery
If you have major problems with your Proxmox VE host, e.g. hardware
issues, it could be helpful to just copy the pmxcfs database file
-/var/lib/pve-cluster/config.db and move it to a new Proxmox VE
+`/var/lib/pve-cluster/config.db` and move it to a new Proxmox VE
host. On the new host (with nothing running), you need to stop the
-pve-cluster service and replace the config.db file (needed permissions
-0600). Second, adapt '/etc/hostname' and '/etc/hosts' according to the
-lost Proxmox VE host, then reboot and check. (And donยดt forget your
+`pve-cluster` service and replace the `config.db` file (needed permissions
+`0600`). Second, adapt `/etc/hostname` and `/etc/hosts` according to the
+lost Proxmox VE host, then reboot and check. (And don't forget your
VM/CT data)
+
Remove Cluster configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
your cluster. This makes sure that all secret cluster/ssh keys and any
shared configuration data is destroyed.
-In some cases, you might prefer to put a node back to local mode
-without reinstall, which is described here:
-
-* stop the cluster file system in '/etc/pve/'
+In some cases, you might prefer to put a node back to local mode without
+reinstall, which is described in
+<<pvecm_separate_node_without_reinstall,Separate A Node Without Reinstalling>>
- # systemctl stop pve-cluster
-* start it again but forcing local mode
+Recovering/Moving Guests from Failed Nodes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- # pmxcfs -l
+For the guest configuration files in `nodes/<NAME>/qemu-server/` (VMs) and
+`nodes/<NAME>/lxc/` (containers), {pve} sees the containing node `<NAME>` as
+owner of the respective guest. This concept enables the usage of local locks
+instead of expensive cluster-wide locks for preventing concurrent guest
+configuration changes.
-* remove the cluster config
+As a consequence, if the owning node of a guest fails (e.g., because of a power
+outage, fencing event, ..), a regular migration is not possible (even if all
+the disks are located on shared storage) because such a local lock on the
+(dead) owning node is unobtainable. This is not a problem for HA-managed
+guests, as {pve}'s High Availability stack includes the necessary
+(cluster-wide) locking and watchdog functionality to ensure correct and
+automatic recovery of guests from fenced nodes.
- # rm /etc/pve/cluster.conf
- # rm /etc/cluster/cluster.conf
- # rm /var/lib/pve-cluster/corosync.authkey
+If a non-HA-managed guest has only shared disks (and no other local resources
+which are only available on the failed node are configured), a manual recovery
+is possible by simply moving the guest configuration file from the failed
+node's directory in `/etc/pve/` to an alive node's directory (which changes the
+logical owner or location of the guest).
-* stop the cluster file system again
+For example, recovering the VM with ID `100` from a dead `node1` to another
+node `node2` works with the following command executed when logged in as root
+on any member node of the cluster:
- # service pve-cluster stop
+ mv /etc/pve/nodes/node1/qemu-server/100.conf /etc/pve/nodes/node2/
-* restart pve services (or reboot)
+WARNING: Before manually recovering a guest like this, make absolutely sure
+that the failed source node is really powered off/fenced. Otherwise {pve}'s
+locking principles are violated by the `mv` command, which can have unexpected
+consequences.
- # service pve-cluster start
- # service pvedaemon restart
- # service pveproxy restart
- # service pvestatd restart
+WARNING: Guest with local disks (or other local resources which are only
+available on the dead node) are not recoverable like this. Either wait for the
+failed node to rejoin the cluster or restore such guests from backups.
+ifdef::manvolnum[]
+include::pve-copyright.adoc[]
+endif::manvolnum[]
projects / pve-docs.git / blobdiff