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1 | Proxmox Cluster file system (pmxcfs) |
2 | ==================================== | |
3 | ||
4 | The Proxmox Cluster file system (pmxcfs) is a database-driven file | |
5 | system for storing configuration files, replicated in real time to all | |
6 | cluster nodes using corosync. We use this to store all PVE related | |
7 | configuration files. | |
8 | ||
9 | Although the file system stores all data inside a persistent database | |
10 | on disk, a copy of the data resides in RAM. That imposes restriction | |
11 | on the maximal size, which is currently 30MB. This is still enough to | |
12 | store the configuration of several thousand virtual machines. | |
13 | ||
14 | Advantages | |
15 | ---------- | |
16 | ||
17 | * seamless replication of all configuration to all nodes in real time | |
18 | * provides strong consistency checks to avoid duplicate VM IDs | |
19 | * read-only when a node looses quorum | |
20 | * automatic updates of the corosync cluster configuration to all nodes | |
21 | * includes a distributed locking mechanism | |
22 | ||
23 | POSIX Compatibility | |
24 | ~~~~~~~~~~~~~~~~~~~ | |
25 | ||
26 | The file system is based on FUSE, so the behavior is POSIX like. But | |
27 | some feature are simply not implemented, because we do not need them: | |
28 | ||
29 | * you can just generate normal files and directories, but no symbolic | |
30 | links, ... | |
31 | ||
32 | * you can't rename non-empty directories (because this makes it easier | |
33 | to guarantee that VMIDs are unique). | |
34 | ||
35 | * you can't change file permissions (permissions are based on path) | |
36 | ||
37 | * `O_EXCL` creates were not atomic (like old NFS) | |
38 | ||
39 | * `O_TRUNC` creates are not atomic (FUSE restriction) | |
40 | ||
41 | ||
42 | File access rights | |
43 | ~~~~~~~~~~~~~~~~~~ | |
44 | ||
45 | All files and directories are owned by user 'root' and have group | |
46 | 'www-data'. Only root has write permissions, but group 'www-data' can | |
47 | read most files. Files below the following paths: | |
48 | ||
49 | /etc/pve/priv/ | |
50 | /etc/pve/nodes/${NAME}/priv/ | |
51 | ||
52 | are only accessible by root. | |
53 | ||
54 | Technology | |
55 | ---------- | |
56 | ||
57 | We use the http://www.corosync.org[Corosync Cluster Engine] for | |
58 | cluster communication, and http://www.sqlite.org[SQlite] for the | |
59 | database file. The filesystem is implemented in user space using | |
60 | http://fuse.sourceforge.net[FUSE]. | |
61 | ||
62 | File system layout | |
63 | ------------------ | |
64 | ||
65 | The file system is mounted at: | |
66 | ||
67 | /etc/pve | |
68 | ||
69 | Files | |
70 | ~~~~~ | |
71 | ||
72 | [width="100%",cols="m,d"] | |
73 | |======= | |
74 | |corosync.conf |corosync cluster configuration file (previous to {pve} 4.x this file was called cluster.conf) | |
75 | |storage.cfg |{pve} storage configuration | |
76 | |user.cfg |{pve} access control configuration (users/groups/...) | |
77 | |domains.cfg |{pve} Authentication domains | |
78 | |authkey.pub | public key used by ticket system | |
79 | |priv/shadow.cfg | shadow password file | |
80 | |priv/authkey.key | private key used by ticket system | |
81 | |nodes/<NAME>/pve-ssl.pem | public ssl key for web server | |
82 | |nodes/<NAME>/priv/pve-ssl.key | private ssl key | |
83 | |nodes/<NAME>/qemu-server/<VMID>.conf | VM configuration data for KVM VMs | |
84 | |nodes/<NAME>/lxc/<VMID>.conf | VM configuration data for LXC containers | |
85 | |firewall/cluster.fw | Firewall config applied to all nodes | |
86 | |firewall/<NAME>.fw | Firewall config for individual nodes | |
87 | |firewall/<VMID>.fw | Firewall config for VMs and Containers | |
88 | |======= | |
89 | ||
90 | Symbolic links | |
91 | ~~~~~~~~~~~~~~ | |
92 | ||
93 | [width="100%",cols="m,m"] | |
94 | |======= | |
95 | |local |nodes/<LOCAL_HOST_NAME> | |
96 | |qemu-server |nodes/<LOCAL_HOST_NAME>/qemu-server/ | |
97 | |lxc |nodes/<LOCAL_HOST_NAME>/lxc/ | |
98 | |======= | |
99 | ||
100 | Special status files for debugging (JSON) | |
101 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
102 | ||
103 | [width="100%",cols="m,d"] | |
104 | |======= | |
105 | | .version |file versions (to detect file modifications) | |
106 | | .members |Info about cluster members | |
107 | | .vmlist |List of all VMs | |
108 | | .clusterlog |Cluster log (last 50 entries) | |
109 | | .rrd |RRD data (most recent entries) | |
110 | |======= | |
111 | ||
112 | Enable/Disable debugging | |
113 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
114 | ||
115 | You can enable verbose syslog messages with: | |
116 | ||
117 | echo "1" >/etc/pve/.debug | |
118 | ||
119 | And disable verbose syslog messages with: | |
120 | ||
121 | echo "0" >/etc/pve/.debug | |
122 | ||
123 | ||
124 | Recovery | |
125 | -------- | |
126 | ||
127 | If you have major problems with your Proxmox VE host, e.g. hardware | |
128 | issues, it could be helpful to just copy the pmxcfs database file | |
129 | /var/lib/pve-cluster/config.db and move it to a new Proxmox VE | |
130 | host. On the new host (with nothing running), you need to stop the | |
131 | pve-cluster service and replace the config.db file (needed permissions | |
132 | 0600). Second, adapt '/etc/hostname' and '/etc/hosts' according to the | |
133 | lost Proxmox VE host, then reboot and check. (And donĀ“t forget your | |
134 | VM/CT data) | |
135 | ||
136 | Remove Cluster configuration | |
137 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
138 | ||
139 | The recommended way is to reinstall the node after you removed it from | |
140 | your cluster. This makes sure that all secret cluster/ssh keys and any | |
141 | shared configuration data is destroyed. | |
142 | ||
143 | In some cases, you might prefer to put a node back to local mode | |
144 | without reinstall, which is described here: | |
145 | ||
146 | * stop the cluster file system in '/etc/pve/' | |
147 | ||
148 | # systemctl stop pve-cluster | |
149 | ||
150 | * start it again but forcing local mode | |
151 | ||
152 | # pmxcfs -l | |
153 | ||
154 | * remove the cluster config | |
155 | ||
156 | # rm /etc/pve/cluster.conf | |
157 | # rm /etc/cluster/cluster.conf | |
158 | # rm /var/lib/pve-cluster/corosync.authkey | |
159 | ||
160 | * stop the cluster file system again | |
161 | ||
162 | # service pve-cluster stop | |
163 | ||
164 | * restart pve services (or reboot) | |
165 | ||
166 | # service pve-cluster start | |
167 | # service pvedaemon restart | |
168 | # service pveproxy restart | |
169 | # service pvestatd restart | |
170 |