数据卷（volume）
由于容器被删除后，其可写的容器层文件并不会保留下来，为了持久化容器的存储，docker提出了数据卷的概念，通过创建数据卷，然后挂载到容器中，从而将容器中的需要持久化存储的数据保存到宿主机上，并且由docker管理数据目录，不用担心具体使用宿主机的哪个目录来进行挂载。
创建数据卷。
docker volume create mysql-server-volume
挂载刚才创建的数据卷，这里用mysql镜像作为示例。
docker run -d --name mysql-server -v mysql-server-volume:/var/lib/mysql -p 3306:3306 -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7.32
此时，mysql数据库的数据都已经存储到数据卷中了，要想看mysql-server-volume数据卷在宿主机的位置，可以用docker inspect containerID，里面Mounts字段有相关的信息，其中Source字段就是数据卷在宿主机的目录。
"Mounts": [
{
"Type": "volume",
"Name": "mysql-server-volume",
"Source": "/var/lib/docker/volumes/mysql-server-volume/_data",
"Destination": "/var/lib/mysql",
"Driver": "local",
"Mode": "z",
"RW": true,
"Propagation": ""
}
],
匿名卷（anonymous volume）
为了防止运行时用户忘记将动态文件所保存目录挂载为数据卷，在Dockerfile中，可以事先指定某些目录挂载为匿名卷，这样在运行时如果用户不指定挂载，那么docker会为其创建匿名卷（anonymous volume）。
VOLUME /data
这里的/data目录就会在容器运行时自动挂载为匿名卷，当然，运行容器时可以覆盖这个挂载设置。比如：
docker run -d -v mydata:/data xxxx
其实mysql的Dockerfile中也指定了匿名卷。
#
# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
#
# PLEASE DO NOT EDIT IT DIRECTLY.
#
FROM debian:buster-slim
# add our user and group first to make sure their IDs get assigned consistently, regardless of whatever dependencies get added
RUN groupadd -r mysql && useradd -r -g mysql mysql
RUN apt-get update && apt-get install -y --no-install-recommends gnupg dirmngr && rm -rf /var/lib/apt/lists/*
# add gosu for easy step-down from root
# https://github.com/tianon/gosu/releases
ENV GOSU_VERSION 1.12
RUN set -eux; \
savedAptMark="$(apt-mark showmanual)"; \
apt-get update; \
apt-get install -y --no-install-recommends ca-certificates wget; \
rm -rf /var/lib/apt/lists/*; \
dpkgArch="$(dpkg --print-architecture | awk -F- '{ print $NF }')"; \
wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$dpkgArch"; \
wget -O /usr/local/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$dpkgArch.asc"; \
export GNUPGHOME="$(mktemp -d)"; \
gpg --batch --keyserver hkps://keys.openpgp.org --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4; \
gpg --batch --verify /usr/local/bin/gosu.asc /usr/local/bin/gosu; \
gpgconf --kill all; \
rm -rf "$GNUPGHOME" /usr/local/bin/gosu.asc; \
apt-mark auto '.*' > /dev/null; \
[ -z "$savedAptMark" ] || apt-mark manual $savedAptMark > /dev/null; \
apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
chmod +x /usr/local/bin/gosu; \
gosu --version; \
gosu nobody true
RUN mkdir /docker-entrypoint-initdb.d
RUN apt-get update && apt-get install -y --no-install-recommends \
# for MYSQL_RANDOM_ROOT_PASSWORD
pwgen \
# for mysql_ssl_rsa_setup
openssl \
# FATAL ERROR: please install the following Perl modules before executing /usr/local/mysql/scripts/mysql_install_db:
# File::Basename
# File::Copy
# Sys::Hostname
# Data::Dumper
perl \
# install "xz-utils" for .sql.xz docker-entrypoint-initdb.d files
xz-utils \
&& rm -rf /var/lib/apt/lists/*
RUN set -ex; \
# gpg: key 5072E1F5: public key "MySQL Release Engineering <mysql-build@oss.oracle.com>" imported
key='A4A9406876FCBD3C456770C88C718D3B5072E1F5'; \
export GNUPGHOME="$(mktemp -d)"; \
gpg --batch --keyserver keyserver.ubuntu.com --recv-keys "$key"; \
gpg --batch --export "$key" > /etc/apt/trusted.gpg.d/mysql.gpg; \
gpgconf --kill all; \
rm -rf "$GNUPGHOME"; \
apt-key list > /dev/null
ENV MYSQL_MAJOR 5.7
ENV MYSQL_VERSION 5.7.36-1debian10
RUN echo 'deb http://repo.mysql.com/apt/debian/ buster mysql-5.7' > /etc/apt/sources.list.d/mysql.list
# the "/var/lib/mysql" stuff here is because the mysql-server postinst doesn't have an explicit way to disable the mysql_install_db codepath besides having a database already "configured" (ie, stuff in /var/lib/mysql/mysql)
# also, we set debconf keys to make APT a little quieter
RUN { \
echo mysql-community-server mysql-community-server/data-dir select ''; \
echo mysql-community-server mysql-community-server/root-pass password ''; \
echo mysql-community-server mysql-community-server/re-root-pass password ''; \
echo mysql-community-server mysql-community-server/remove-test-db select false; \
} | debconf-set-selections \
&& apt-get update \
&& apt-get install -y \
mysql-server="${MYSQL_VERSION}" \
# comment out a few problematic configuration values
&& find /etc/mysql/ -name '*.cnf' -print0 \
| xargs -0 grep -lZE '^(bind-address|log)' \
| xargs -rt -0 sed -Ei 's/^(bind-address|log)/#&/' \
# don't reverse lookup hostnames, they are usually another container
&& echo '[mysqld]\nskip-host-cache\nskip-name-resolve' > /etc/mysql/conf.d/docker.cnf \
&& rm -rf /var/lib/apt/lists/* \
&& rm -rf /var/lib/mysql && mkdir -p /var/lib/mysql /var/run/mysqld \
&& chown -R mysql:mysql /var/lib/mysql /var/run/mysqld \
# ensure that /var/run/mysqld (used for socket and lock files) is writable regardless of the UID our mysqld instance ends up having at runtime
&& chmod 1777 /var/run/mysqld /var/lib/mysql
VOLUME /var/lib/mysql
COPY docker-entrypoint.sh /usr/local/bin/
RUN ln -s usr/local/bin/docker-entrypoint.sh /entrypoint.sh # backwards compat
ENTRYPOINT ["docker-entrypoint.sh"]
EXPOSE 3306 33060
CMD ["mysqld"]
所以直接运行mysql容器会自动创建匿名卷。
docker run -d --name mysql-server -p 3306:3306 -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7.32
查看刚创建的匿名卷。
[rc@localhost ~]$ docker volume ls
DRIVER VOLUME NAME
local 5bdd98b079c49da27c2ac457ca593b3fe87b4c6c9742051c094ea18e29b061a5