Understand Debug & Error Logs

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As of October 4, 2019, CockroachDB v2.0 is no longer supported. For more details, refer to the Release Support Policy.

If you need to troubleshoot issues with your cluster, you can check a node's logs, which include details about certain node-level and range-level events, such as errors. For example, if CockroachDB crashes, it normally logs a stack trace to what caused the problem.


For detailed information about queries being executed against your system, see SQL Audit Logging.


When a node processes a cockroach command, it produces a stream of messages about the command's activities. Each message's body describes the activity, and its envelope contains metadata such as the message's severity level.

As a command generates messages, CockroachDB uses the command's logging flags and the message's severity level to determine the appropriate location for it.

Each node's logs detail only the internal activity of that node without visibility into the behavior of other nodes in the cluster. When troubleshooting, this means that you must identify the node where the problem occurred or collect the logs from all active nodes in your cluster.


All cockroach commands support logging. However, it's important to note:

  • cockroach start generates most messages related to the operation of your cluster.
  • Other commands do generate messages, but they're typically only interesting in troubleshooting scenarios.

Severity Levels

CockroachDB identifies each message with a severity level, letting operators know if they need to intercede:

  1. INFO (lowest severity; no action necessary)
  3. ERROR
  4. FATAL (highest severity; requires operator attention)

Default Behavior by Severity Level

Command INFO messages WARNING and above messages
cockroach start Write to file Write to file
All other commands Discard Print to stderr

Output Locations

Based on the command's flags and the message's severity level, CockroachDB does one of the following:

Write to File

CockroachDB can write messages to log files. The files are named using the following format:

cockroach.[host].[user].[start timestamp in UTC].[process ID].log

For example:

All log file timestamps are in UTC because CockroachDB is designed to be deployed in a distributed cluster. Nodes may be located in different time zones, and using UTC makes it easy to correlate log messages from those nodes no matter where they are located.
Property cockroach start All other commands
Enabled by Default1 Explicit --log-dir flag
Default File Destination [firststoredir]/logs N/A
Change File Destination --log-dir=[destination] --log-dir=[destination]
Default Severity Level Threshold INFO N/A
Change Severity Threshold --log-file-verbosity=[severity level] --log-file-verbosity=[severity level]
Disabled by --log-dir=1 Default
1 If the cockroach process does not have access to on-disk storage, cockroach start does not write messages to log files; instead it prints all messages to stderr.

CockroachDB can print messages to stderr, which normally prints them to the machine's terminal but does not store them.

Property cockroach start All other commands
Enabled by Explicit --logtostderr flag2 Default
Default Severity Level Threshold N/A WARNING
Change Severity Threshold --logtostderr=[severity level] --logtostderr=[severity level]
Disabled by Default2 --logtostderr=NONE
2 cockroach start does not print any messages to stderr unless the cockroach process does not have access to on-disk storage, in which case it defaults to --logtostderr=INFO and prints all messages to stderr.

Discard Message

Messages with severity levels below the --logtostderr and --log-file-verbosity flag's values are neither written to files nor printed to stderr, so they are discarded.

By default, commands besides cockroach start discard messages with the INFO severity level.


Flag Description
--log-dir Enable logging to files and write logs to the specified directory.

Setting --log-dir to a blank directory (--log-dir=) disables logging to files. Do not use --log-dir=""; this creates a new directory named "" and stores log files in that directory.
--log-dir-max-size After the log directory reaches the specified size, delete the oldest log file. The flag's argument takes standard file sizes, such as --log-dir-max-size=1GiB.

Default: 100MiB
--log-file-max-size After logs reach the specified size, begin writing logs to a new file. The flag's argument takes standard file sizes, such as --log-file-max-size=2MiB.

Default: 10MiB
--log-file-verbosity Only writes messages to log files if they are at or above the specified severity level, such as --log-file-verbosity=WARNING. Requires logging to files.

Default: INFO
--logtostderr Enable logging to stderr for messages at or above the specified severity level, such as --logtostderr=ERROR

If you use this flag without specifying the severity level (e.g., cockroach start --logtostderr), it prints messages of all severities to stderr.

Setting --logtostderr=NONE disables logging to stderr.
--no-color Do not colorize stderr. Possible values: true or false.

When set to false, messages logged to stderr are colorized based on severity level.

Default: false
--sql-audit-dir New in v2.0: If non-empty, create a SQL audit log in this directory. By default, SQL audit logs are written in the same directory as the other logs generated by CockroachDB. For more information, see SQL Audit Logging.

The --log-backtrace-at, --verbosity, and --v flags are intended for internal debugging by CockroachDB contributors.

See Also

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