> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-fix-nav-issues.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Troubleshooting

> Installation troubleshooting guide

<h2 id="installation">
  Installation
</h2>

<h3 id="cant-import-gpg-keys-from-keyserverubuntucom-with-apt-key">
  Can't import GPG keys from keyserver.ubuntu.com with apt-key
</h3>

The `apt-key` feature with the [Advanced package tool (APT) has been deprecated](https://manpages.debian.org/bookworm/apt/apt-key.8.en.html). You should use the `gpg` command instead. Please refer the [install guide](/get-started/setup/install) article.

<h3 id="cant-import-gpg-keys-from-keyserverubuntucom-with-gpg">
  Can't import GPG keys from keyserver.ubuntu.com with gpg
</h3>

1. See if your `gpg` is installed:

```shell theme={null}
sudo apt-get install gnupg
```

<h3 id="cant-get-deb-packages-from-clickhouse-repository-with-apt-get">
  Can't get deb packages from ClickHouse repository with apt-get
</h3>

1. Check firewall settings.
2. If you can't access the repository for any reason, download packages as described in the [install guide](/get-started/setup/install) article and install them manually using the `sudo dpkg -i <packages>` command. You will also need the `tzdata` package.

<h3 id="cant-update-deb-packages-from-clickhouse-repository-with-apt-get">
  Can't update deb packages from ClickHouse repository with apt-get
</h3>

The issue may be happened when the GPG key is changed.

Please use the manual from the [setup](/get-started/setup/self-managed/debian-ubuntu) page to update the repository configuration.

<h3 id="you-get-different-warnings-with-apt-get-update">
  You get different warnings with `apt-get update`
</h3>

The completed warning messages are as one of following:

```shell theme={null}
N: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'https://packages.clickhouse.com/deb stable InRelease' doesn't support architecture 'i386'
```

```shell theme={null}
E: Failed to fetch https://packages.clickhouse.com/deb/dists/stable/main/binary-amd64/Packages.gz  File has unexpected size (30451 != 28154). Mirror sync in progress?
```

```shell theme={null}
E: Repository 'https://packages.clickhouse.com/deb stable InRelease' changed its 'Origin' value from 'Artifactory' to 'ClickHouse'
E: Repository 'https://packages.clickhouse.com/deb stable InRelease' changed its 'Label' value from 'Artifactory' to 'ClickHouse'
N: Repository 'https://packages.clickhouse.com/deb stable InRelease' changed its 'Suite' value from 'stable' to ''
N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
```

```shell theme={null}
Err:11 https://packages.clickhouse.com/deb stable InRelease
400  Bad Request [IP: 172.66.40.249 443]
```

To resolve the above issue, please use the following script:

```shell theme={null}
sudo rm /var/lib/apt/lists/packages.clickhouse.com_* /var/lib/dpkg/arch /var/lib/apt/lists/partial/packages.clickhouse.com_*
sudo apt-get clean
sudo apt-get autoclean
```

<h3 id="cant-get-packages-with-yum-because-of-wrong-signature">
  Can't get packages with Yum because of wrong signature
</h3>

Possible issue: the cache is wrong, maybe it's broken after updated GPG key in 2022-09.

The solution is to clean out the cache and lib directory for Yum:

```shell theme={null}
sudo find /var/lib/yum/repos/ /var/cache/yum/ -name 'clickhouse-*' -type d -exec rm -rf {} +
sudo rm -f /etc/yum.repos.d/clickhouse.repo
```

After that follow the [install guide](/get-started/setup/self-managed/redhat)

<h2 id="connecting-to-the-server">
  Connecting to the server
</h2>

Possible issues:

* The server isn't running.
* Unexpected or wrong configuration parameters.

<h3 id="server-is-not-running">
  Server isn't running
</h3>

<h4 id="check-if-server-is-running">
  Check if server is running
</h4>

```shell theme={null}
sudo service clickhouse-server status
```

If the server isn't running, start it with the command:

```shell theme={null}
sudo service clickhouse-server start
```

<h4 id="check-the-logs">
  Check the logs
</h4>

The main log of `clickhouse-server` is in `/var/log/clickhouse-server/clickhouse-server.log` by default.

If the server started successfully, you should see the strings:

* `<Information> Application: starting up.` — Server started.
* `<Information> Application: Ready for connections.` — Server is running and ready for connections.

If `clickhouse-server` start failed with a configuration error, you should see the `<Error>` string with an error description. For example:

```plaintext theme={null}
2019.01.11 15:23:25.549505 [ 45 ] {} <Error> ExternalDictionaries: Failed reloading 'event2id' external dictionary: Poco::Exception. Code: 1000, e.code() = 111, e.displayText() = Connection refused, e.what() = Connection refused
```

If you don't see an error at the end of the file, look through the entire file starting from the string:

```plaintext theme={null}
<Information> Application: starting up.
```

If you try to start a second instance of `clickhouse-server` on the server, you see the following log:

```plaintext theme={null}
2019.01.11 15:25:11.151730 [ 1 ] {} <Information> : Starting ClickHouse 19.1.0 with revision 54413
2019.01.11 15:25:11.154578 [ 1 ] {} <Information> Application: starting up
2019.01.11 15:25:11.156361 [ 1 ] {} <Information> StatusFile: Status file ./status already exists - unclean restart. Contents:
PID: 8510
Started at: 2019-01-11 15:24:23
Revision: 54413

2019.01.11 15:25:11.156673 [ 1 ] {} <Error> Application: DB::Exception: Cannot lock file ./status. Another server instance in same directory is already running.
2019.01.11 15:25:11.156682 [ 1 ] {} <Information> Application: shutting down
2019.01.11 15:25:11.156686 [ 1 ] {} <Debug> Application: Uninitializing subsystem: Logging Subsystem
2019.01.11 15:25:11.156716 [ 2 ] {} <Information> BaseDaemon: Stop SignalListener thread
```

<h4 id="see-systemd-logs">
  See system.d logs
</h4>

If you don't find any useful information in `clickhouse-server` logs or there aren't any logs, you can view `system.d` logs using the command:

```shell theme={null}
sudo journalctl -u clickhouse-server
```

<h4 id="start-clickhouse-server-in-interactive-mode">
  Start clickhouse-server in interactive mode
</h4>

```shell theme={null}
sudo -u clickhouse /usr/bin/clickhouse-server --config-file /etc/clickhouse-server/config.xml
```

This command starts the server as an interactive app with standard parameters of the autostart script. In this mode `clickhouse-server` prints all the event messages in the console.

<h3 id="configuration-parameters">
  Configuration parameters
</h3>

Check:

1. Docker settings:

   * If you run ClickHouse in Docker in an IPv6 network, make sure that `network=host` is set.

2. Endpoint settings.
   * Check [listen\_host](/reference/settings/server-settings/settings#listen_host) and [tcp\_port](/reference/settings/server-settings/settings#tcp_port) settings.
   * ClickHouse server accepts localhost connections only by default.

3. HTTP protocol settings:

   * Check protocol settings for the HTTP API.

4. Secure connection settings.

   * Check:
     * The [tcp\_port\_secure](/reference/settings/server-settings/settings#tcp_port_secure) setting.
     * Settings for [SSL certificates](/reference/settings/server-settings/settings#openssl).
   * Use proper parameters while connecting. For example, use the `port_secure` parameter with `clickhouse_client`.

5. User settings:

   * You might be using the wrong user name or password.

<h2 id="query-processing">
  Query processing
</h2>

If ClickHouse isn't able to process the query, it sends an error description to the client. In the `clickhouse-client` you get a description of the error in the console. If you're using the HTTP interface, ClickHouse sends the error description in the response body. For example:

```shell theme={null}
$ curl 'http://localhost:8123/' --data-binary "SELECT a"
Code: 47, e.displayText() = DB::Exception: Unknown identifier: a. Note that there are no tables (FROM clause) in your query, context: required_names: 'a' source_tables: table_aliases: private_aliases: column_aliases: public_columns: 'a' masked_columns: array_join_columns: source_columns: , e.what() = DB::Exception
```

If you start `clickhouse-client` with the `stack-trace` parameter, ClickHouse returns the server stack trace with the description of an error.

You might see a message about a broken connection. In this case, you can repeat the query. If the connection breaks every time you perform the query, check the server logs for errors.

<h2 id="efficiency-of-query-processing">
  Efficiency of query processing
</h2>

If you see that ClickHouse is working too slowly, you need to profile the load on the server resources and network for your queries.

You can use the clickhouse-benchmark utility to profile queries. It shows the number of queries processed per second, the number of rows processed per second, and percentiles of query processing times.