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发表于 更新于 分类于 阅读次数： Waline：

在Docker容器中执行systemctl命令时，无论是启动nginx, 或者是vsftpd等服务，都会报如下错误。

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systemctl status vsftpd
Failed to get D-Bus connection: Operation not permitted

解决方法

  1. 在启动容器时，需要加上--privileged参数来添加权限。
  2. 不能使用默认的bash，而需要执行/usr/sbin/init

执行命令：

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docker run -dit --privileged <image_id> /usr/sbin/init

以下我们以安装启动vsftpd服务来例子来讲解。

启动centos的容器

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docker run -dit --privileged 3816db78c729 /usr/sbin/init

进入刚才启动的容器

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docker exec -it d9c3cf1ad7a bash

yum安装vsftpd服务

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yum install -y vsftpd

启动vsftpd服务

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systemctl start vsftpd

查看vsftpd服务的状态

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systemctl status vsftpd
● vsftpd.service - Vsftpd ftp daemon
   Loaded: loaded (/usr/lib/systemd/system/vsftpd.service; disabled; vendor preset: disabled)
   Active: active (running) since Sat 2019-11-16 03:55:51 UTC; 2s ago
  Process: 176 ExecStart=/usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf (code=exited, status=0/SUCCESS)
 Main PID: 177 (vsftpd)
   CGroup: /docker/d9c3cf1ad7a9084f7563169cbac71b7a5687ebc25703c43f31b6f33a59e686e6/system.slice/vsftpd.service
           └─177 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
           ‣ 177 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf

Nov 16 03:55:51 d9c3cf1ad7a9 systemd[1]: Starting Vsftpd ftp daemon...
Nov 16 03:55:51 d9c3cf1ad7a9 systemd[1]: Started Vsftpd ftp daemon.

发表于 更新于 分类于 ， 阅读次数： Waline：

为了测试把NFS文件系统的共享目录挂载到本地，特意启动了Docker容器来做实验。

执行命令时，必须加入--privileged这个参数，不然在Mount时会报permission denied的错误。

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docker run -d --privileged <image_id>

查看NFS的共享目录

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showmount -e 172.17.0.2
Export list for 172.17.0.2:
/nfs/share *

也可以到NFS服务器上查看/etc/exports文件的内容。

执行挂载命令

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mount -t nfs 172.17.0.2:/nfs/share /mnt/nfs/

会报如下错误：

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mount: wrong fs type, bad option, bad superblock on 172.17.0.2:/nfs/share,
       missing codepage or helper program, or other error
       (for several filesystems (e.g. nfs, cifs) you might
       need a /sbin/mount.<type> helper program)

       In some cases useful info is found in syslog - try
       dmesg | tail or so.

解决办法即是安装NFS的依赖包。

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yum install -y nfs-utils

安装成功后，再次mount就可以成功了。

发表于 更新于 分类于 阅读次数： Waline：

当前ubuntu环境

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cat /etc/issue
Ubuntu 19.04 \n \l

当我们查看文件系统占用情况时，发现有/dev/loop0至/dev/loop7占用率为100%。

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df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            3.9G     0  3.9G   0% /dev
tmpfs           796M  1.9M  794M   1% /run
/dev/sda1        20G   18G  1.1G  95% /
tmpfs           3.9G     0  3.9G   0% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/loop0       15M   15M     0 100% /snap/gnome-characters/254
/dev/loop2       90M   90M     0 100% /snap/core/6673
/dev/loop1      3.8M  3.8M     0 100% /snap/gnome-system-monitor/77
/dev/loop3      152M  152M     0 100% /snap/gnome-3-28-1804/31
/dev/loop4       36M   36M     0 100% /snap/gtk-common-themes/1198
/dev/loop7      1.0M  1.0M     0 100% /snap/gnome-logs/61
/dev/loop6       54M   54M     0 100% /snap/core18/941
/dev/loop5      4.2M  4.2M     0 100% /snap/gnome-calculator/406
tmpfs           796M   36K  795M   1% /run/user/1000

/dev/loopn这些设备在Linux下被称为回环设备。

可以通过执行losetup命令查看所有回环设备。

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losetup
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE                                         DIO LOG-SEC
/dev/loop1         0      0         1  1 /var/lib/snapd/snaps/gnome-system-monitor_77.snap   0     512
/dev/loop6         0      0         1  1 /var/lib/snapd/snaps/core18_941.snap                0     512
/dev/loop4         0      0         1  1 /var/lib/snapd/snaps/gtk-common-themes_1198.snap    0     512
/dev/loop2         0      0         1  1 /var/lib/snapd/snaps/core_6673.snap                 0     512
/dev/loop0         0      0         1  1 /var/lib/snapd/snaps/gnome-characters_254.snap      0     512
/dev/loop7         0      0         1  1 /var/lib/snapd/snaps/gnome-logs_61.snap             0     512
/dev/loop5         0      0         1  1 /var/lib/snapd/snaps/gnome-calculator_406.snap      0     512
/dev/loop3         0      0         1  1 /var/lib/snapd/snaps/gnome-3-28-1804_31.snap        0     512

我们可以把xxx.iso镜像文件挂载到一个目录下。

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mount -o loop xxx.iso /media

等同于执行：

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losetup /dev/loop0 xxx.iso
mount /dev/loop0 /media

清理方法

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sudo apt autoremove --purge snapd
[sudo] password for simon: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  gnome-software gnome-software-common
Suggested packages:
  apt-config-icons-hidpi gnome-software-plugin-flatpak
Recommended packages:
  gnome-software-plugin-snap
The following packages will be REMOVED:
  apg* gnome-control-center-faces* gnome-online-accounts* gnome-software-plugin-snap* libclutter-imcontext-0.1-0* libclutter-imcontext-0.1-bin*
  libcolord-gtk1* libgsound0* libgtop-2.0-11* libgtop2-common* mobile-broadband-provider-info* network-manager-gnome* python3-macaroonbakery*
  python3-protobuf* python3-rfc3339* python3-tz* snapd* ubuntu-system-service*
The following packages will be upgraded:
  gnome-software gnome-software-common
2 upgraded, 0 newly installed, 18 to remove and 171 not upgraded.
Need to get 2,982 kB of archives.
After this operation, 73.7 MB disk space will be freed.
Do you want to continue? [Y/n] y

再次查看磁盘使用情况：

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df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            3.9G     0  3.9G   0% /dev
tmpfs           796M  1.9M  794M   1% /run
/dev/sda1        20G   18G  1.6G  92% /
tmpfs           3.9G     0  3.9G   0% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           3.9G     0  3.9G   0% /sys/fs/cgroup
tmpfs           796M   36K  795M   1% /run/user/1000
0%