错误信息：docker:Permission denied:/var/run/docker.sock
docker修改执行权限
docker因为安装是root用户下的，所以每次启动都需要在用户环境下加上sudo操作。这样似乎十分不方便。
而且每次顺手docker ps或者docker images都会报错：
Got permission denied ... /var/run/docker.sock: connect: permission denied
于是可以更改一下docker的用户操作权限：
先给出用到的命令：
sudo usermod -aG docker $USER
newgrp docker
systemctl restart docker
# 或者service docker restart
以上就可将docker的权限更改为非root用户下执行。
这里用到两个命令usermod和newgrp
usermod
The usermodcommand modifies the system account files to reflect the changes that are specified on the command line.
usermod --help
Usage: usermod [options] LOGIN
Options:
-c, --comment COMMENT new value of the GECOS field
-d, --home HOME_DIR new home directory for the user account
-e, --expiredate EXPIRE_DATE set account expiration date to EXPIRE_DATE
-f, --inactive INACTIVE set password inactive after expiration
to INACTIVE
-g, --gid GROUP force use GROUP as new primary group
-G, --groups GROUPS new list of supplementary GROUPS
-a, --append append the user to the supplemental GROUPS
mentioned by the -G option without removing
him/her from other groups
-h, --help display this help message and exit
-l, --login NEW_LOGIN new value of the login name
-L, --lock lock the user account
-m, --move-home move contents of the home directory to the
new location (use only with -d)
-o, --non-unique allow using duplicate (non-unique) UID
-p, --password PASSWORD use encrypted password for the new password
-R, --root CHROOT_DIR directory to chroot into
-s, --shell SHELL new login shell for the user account
-u, --uid UID new UID for the user account
-U, --unlock unlock the user account
-v, --add-subuids FIRST-LAST add range of subordinate uids
-V, --del-subuids FIRST-LAST remove range of subordinate uids
-w, --add-subgids FIRST-LAST add range of subordinate gids
-W, --del-subgids FIRST-LAST remove range of subordinate gids
-Z, --selinux-user SEUSER new SELinux user mapping for the user account
例子：
usermod -G staff newuser2 # 将newuser2添加到组staff中
newgrp
The newgrp commandis used to change the current group ID (GID) during a login session.
newgrp --help
Usage: newgrp [-] [group]
