ubuntu中/dev/zero是块设备吗

是的，/dev/zero是一个块设备。它是一个特殊的设备文件，可以用于生成一个无限的流数据，其中所有字节都是零。它通常用于初始化内存或磁盘空间，也可以用于测试和调试目的。在Linux系统中，块设备是指可以被分成固定大小块（通常是512字节）的设备，例如硬盘、U盘等。而/dev/zero就是一个虚拟的块设备。

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ubuntu mysql8.0.32 /etc/mysql/my.cnf 文件内容

以下是在Ubuntu系统上安装MySQL 8.0.32后的默认 /etc/mysql/my.cnf 文件内容：

# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
# 
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html

[mysqld]
#
# * Basic Settings
#
user                           = mysql
pid-file                       = /var/run/mysqld/mysqld.pid
socket                         = /var/run/mysqld/mysqld.sock
basedir                        = /usr
datadir                        = /var/lib/mysql
tmpdir                         = /tmp
lc-messages-dir                = /usr/share/mysql
#skip-external-locking
skip-name-resolve
skip-host-cache
skip-ssl
sql-mode                       = ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
log-error                      = /var/log/mysql/error.log

# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

# Recommended in standard MySQL setup
# sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

#
# * Character sets
#
# MySQL/MariaDB default is Latin1, but in Ubuntu UTF-8 is default
#
character-set-server  = utf8mb4
collation-server      = utf8mb4_general_ci

#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#

#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates you can use for example the GUI tool "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem

[mysql]
#
# * Basic Settings
#
socket                         = /var/run/mysqld/mysqld.sock
prompt                         = \u@\h [\d]>\_

[mysqldump]
#
# * Basic Settings
#
socket                         = /var/run/mysqld/mysqld.sock
quick
quote-names
max_allowed_packet             = 16M

[isamchk]
key_buffer                     = 16M

#
# * IMPORTANT: Additional settings that can override those from this file!
#   The files must end with '.cnf', otherwise they'll be ignored.
#
!includedir /etc/mysql/conf.d/

注意，这只是默认的配置文件，实际上你可以根据需要进行修改。

/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/buildroot/output/rockchip_rk3399/.rockchipconfig:339:warning: override: reassigning to symbol BR2_PACKAGE_NTFS_3G # # configuration written to /home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/buildroot/output/rockchip_rk3399/.config # make: Leaving directory '/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/buildroot' you need to install 'unbuffer' (from package expect or expect-dev) log saved on /home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/br.log tail: cannot open '/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/br.log' for reading: No such file or directory Command exited with non-zero status 1 you take 0:04.44 to build builroot ====Build buildroot failed!====

根据你提供的输出，这是在构建 Buildroot 时遇到的一些警告和错误。

首先，警告显示 `/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/buildroot/output/rockchip_rk3399/.rockchipconfig` 文件中的第 339 行出现了一个警告，指示重新分配了符号 `BR2_PACKAGE_NTFS_3G`。这可能意味着在配置文件中对该符号进行了重复赋值。

然后，输出显示配置已写入 `/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/buildroot/output/rockchip_rk3399/.config` 文件。

接下来，输出显示离开了 `/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/buildroot` 目录。

然后，输出显示需要安装 `unbuffer` 工具。它建议你从 `expect` 或 `expect-dev` 包中安装 `unbuffer`。

然后，输出显示日志保存在 `/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/br.log` 文件中。

最后，输出显示尝试读取 `/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/br.log` 文件时出现错误，表示该文件不存在。

根据上述警告和错误，你可以尝试做以下几件事情：

1. 检查配置文件中是否对 `BR2_PACKAGE_NTFS_3G` 进行了重复赋值。打开 `/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/buildroot/output/rockchip_rk3399/.rockchipconfig` 文件，并检查第 339 行的设置。

2. 检查是否已经安装了 `expect` 或 `expect-dev` 包。你可以使用合适的软件包管理器来安装它们。例如，在 Ubuntu 或基于 Debian 的系统上，你可以使用以下命令：

   sudo apt-get install expect

3. 检查构建日志是否存在。确认 `/home/clzdh/Desktop/rk3399_linux_release_v2.5.1_20210301/br.log` 文件是否存在，如果不存在，可能是由于构建过程中出现问题导致的。

如果问题仍然存在，请提供更多的上下文或详细描述你的构建环境和步骤，以便我们能够更好地帮助你解决问题。