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# Running

## Starting Stellar Core​

Once you've set up your environment, configured your node, set up your quorum set, and selected archives to get history from, you're ready to start Stellar Core.

Use a command equivalent to:

$stellar-core run At this point, you're ready to observe your node's activity as it joins the network. You may want to skip ahead and review the logging section to familiarize yourself wiith Stellar Core's output. ## Interacting With Your Instance​ When your node is running, you can interact with Stellar Core via an administrative HTTP endpoint. Commands can be submitted using command-line HTTP tools such as curl, or by running a command such as $ stellar-core http-command <http-command>

That HTTP endpoint is not intended to be exposed to the public internet. It's typically accessed by administrators, or by a mid-tier application to submit transactions to the Stellar network.

See commands for a description of the available commands.

## Joining the Network​

Your node will go through the following phases as it joins the network:

### Establishing Connection to Other Peers.​

You should see authenticated_count increase.

"peers" : {   "authenticated_count" : 3,   "pending_count" : 4},

### Observing Consensus​

Until the node sees a quorum, it will say:

"state" : "Joining SCP"

After observing consensus, a new field quorum will display information about network decisions. At this point the node will switch to "Catching up":

"quorum" : {   "qset" : {      "ledger" : 22267866,      "agree" : 5,      "delayed" : 0,      "disagree" : 0,      "fail_at" : 3,      "hash" : "980a24",      "missing" : 0,      "phase" : "EXTERNALIZE"   },   "transitive" : {      "intersection" : true,      "last_check_ledger" : 22267866,      "node_count" : 21   }},"state" : "Catching up",

### Catching up​

This is a phase where the node downloads data from archives. The state will start with something like:

"state" : "Catching up","status" : [ "Catching up: Awaiting checkpoint (ETA: 35 seconds)" ]

And then go through the various phases of downloading and applying state such as

"state" : "Catching up","status" : [ "Catching up: downloading ledger files 20094/119803 (16%)" ]

You can specify how far back your node goes to catch up in your config file. If you setCATCHUP_COMPLETE to true, your node will replay the entire history of the network, which can take a long time. Weeks. Satoshipay offers a parallel catchup script to speed up the process, but you only need to replay the complete network history if you're setting up a Full Validator. Otherwise, you can specify a starting point for catchup using CATCHUP_RECENT. See the complete example configuration for more details.

### Synced​

When the node is done catching up, its state will change to:

"state" : "Synced!"

## Logging​

Stellar Core sends logs to standard output and stellar-core.log by default, configurable as LOG_FILE_PATH.

Log messages are classified by progressive priority levels:TRACE, DEBUG, INFO, WARNING, ERROR and FATAL. The logging system only emits those messages at or above its configured logging level.

The log level can be controlled by configuration, the -ll command-line flag, or adjusted dynamically by administrative (HTTP) commands. To do so, run:

$stellar-core http-command "ll?level=debug" while your system is running. Log levels can also be adjusted on a partition-by-partition basis through the administrative interface. For example the history system can be set to DEBUG-level logging by running: $ stellar-core http-command "ll?level=debug&partition=history"

Against a running system.

The default log level is INFO, which is moderately verbose and should emit progress messages every few seconds under normal operation.

## Validator maintenance​

Maintenance here refers to anything involving taking your validator temporarily out of the network (to apply security patches, system upgrade, etc).

As an administrator of a validator, you must ensure that the maintenance you are about to apply to the validator is safe for the overall network and for your validator.

Safe means that the other validators that depend on yours will not be affected too much when you turn off your validator for maintenance and that your validator will continue to operate as part of the network when it comes back up.

If you are changing some settings that may impact network wide settings such as protocol version, review the section on network configuration.

If you're changing your quorum set configuration, also read the section on what to do.

We recommend performing the following steps in order (repeat sequentially as needed if you run multiple nodes).

1. Advertise your intention to others that may depend on you. Some coordination is required to avoid situations where too many nodes go down at the same time.
2. Dependencies should assess the health of their quorum, refer to the section "Understanding quorum and reliability".
3. If there is no objection, take your instance down
4. When done, start your instance that should rejoin the network
5. The instance will be completely caught up when it's both Synced and there is no backlog in uploading history.

#### Special considerations during quorum set updates​

Sometimes an organization needs to make changes that impact other's quorum sets:

• taking a validator down for long period of time
• adding new validators to their pool

In both cases, it's crucial to stage the changes to preserve quorum intersection and general good health of the network:

• removing too many nodes from your quorum set before the nodes are taken down : if different people remove different sets the remaining sets may not overlap between nodes and may cause network splits
• adding too many nodes in your quorum set at the same time : if not done carefully can cause those nodes to overpower your configuration

Recommended steps are for the entity that adds/removes nodes to do so first between their own nodes, and then have people reflect those changes gradually (over several rounds) in their quorum configuration.