为什么sudo apt升级不能在Ubuntu上运行?

我正试图在我的服务器上安装升级,但我收到了这个“错误”。

我是Ubuntu的新手,所以如果你需要任何信息来帮助我,请随时询问!

user@server~$ sudo apt upgrade

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
Get more security updates through Ubuntu Pro with 'esm-apps' enabled:
  libldns-dev libldns3 libjs-jquery-ui libavdevice58 libpostproc55 php-twig
  libavcodec58 libavutil56 libswscale5 libswresample3 libavformat58
  libpmix-dev libpmix2 libavfilter7
Learn more about Ubuntu Pro at https://ubuntu.com/pro
The following packages will be upgraded:
  postfix
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
3 not fully installed or removed.
1 standard LTS security update
Need to get 0 B/1,248 kB of archives.
After this operation, 1,024 B of additional disk space will be used.
Do you want to continue? [Y/n] y
debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable
(Reading database ... 174475 files and directories currently installed.)
Preparing to unpack .../postfix_3.6.4-1ubuntu1.3_amd64.deb ...
debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable
dpkg: error processing archive /var/cache/apt/archives/postfix_3.6.4-1ubuntu1.3_amd64.deb (--unpack):
 new postfix package pre-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 /var/cache/apt/archives/postfix_3.6.4-1ubuntu1.3_amd64.deb
needrestart is being skipped since dpkg has failed
E: Sub-process /usr/bin/dpkg returned an error code (1)

我试着在网上搜索解决方案,但什么也找不到。