什麼是容器？在生活中我們常見的容器有各種瓶瓶罐罐、各種能夠容納其它物料的東西叫容器；容器的特點就是有著很好的隔離作用，使得不同的物料互相隔離；除此之外容器還方便運輸、方便儲存；這是生活中所說的容器，以及它的特點；在計算機領域中，所謂容器不外乎也有同生活中的容器的特點，隔離，方便“運輸”（計算機中的運輸我們叫移植，從系統A到系統B），方便“儲存”（這裡指程式以及執行所依賴的庫檔案打包，即程式及執行時環境打包）；LXC是Linux containers的縮寫，意思就是Linux 容器；Linux容器技術其實就是整合核心的功能，讓其支援多個容器執行時資源相互隔離；我們知道核心的功能使用者是無法直接操作的，必須得有一使用者空間的軟體，通過系統呼叫去操作核心功能；所以lxc就是用來操作Linux核心容器化的工具；這種邏輯有點類似iptables，iptables本身不對使用者的報文做任何檢查，真正生效的是核心netfilter;
LXC關鍵技術點：
1、chroot：根切換，一個改變當前執行程式以及其子程式的根目錄的操作。一個執行在這種環境的程式無法訪問根目錄外的檔案和命令。
2、namespaces：名稱空間，LXC在隔離控制方面依賴於Linux核心的namespace特性，具體而言就是在clone時加入相應的flag；
3、CGroups：控制組，LXC在資源管理方面依賴於Linux核心的cgroups子系統，cgroups子系統是Linux核心提供的一個基於程式組的資源管理的框架，可以為特定的程式組限定可以使用的資源；
LXC簡單使用：
1、安裝LXC工具
[root@lxc ~]# yum install lxc-* libcgroup* bridge-utils Loaded plugins: fastestmirror base | 3.6 kB 00:00:00 epel | 4.7 kB 00:00:00 extras | 2.9 kB 00:00:00 updates | 2.9 kB 00:00:00 (1/7): base/7/x86_64/group_gz | 153 kB 00:00:00 (2/7): epel/x86_64/group_gz | 95 kB 00:00:00 (3/7): epel/x86_64/updateinfo | 1.0 MB 00:00:00 (4/7): updates/7/x86_64/primary_db | 1.3 MB 00:00:00 (5/7): extras/7/x86_64/primary_db | 190 kB 00:00:00 (6/7): base/7/x86_64/primary_db | 6.1 MB 00:00:01 (7/7): epel/x86_64/primary_db | 6.8 MB 00:00:02 Determining fastest mirrors * base: mirrors.aliyun.com * extras: mirrors.aliyun.com * updates: mirrors.aliyun.com Resolving Dependencies --> Running transaction check ---> Package bridge-utils.x86_64 0:1.5-9.el7 will be installed ---> Package libcgroup.x86_64 0:0.41-21.el7 will be installed ---> Package libcgroup-devel.x86_64 0:0.41-21.el7 will be installed ---> Package libcgroup-pam.x86_64 0:0.41-21.el7 will be installed ……省略部分資訊 Installed: bridge-utils.x86_64 0:1.5-9.el7 libcgroup.x86_64 0:0.41-21.el7 libcgroup-devel.x86_64 0:0.41-21.el7 libcgroup-pam.x86_64 0:0.41-21.el7 libcgroup-tools.x86_64 0:0.41-21.el7 lxc.x86_64 0:1.0.11-2.el7 lxc-devel.x86_64 0:1.0.11-2.el7 lxc-doc.noarch 0:1.0.11-2.el7 lxc-extra.x86_64 0:1.0.11-2.el7 lxc-libs.x86_64 0:1.0.11-2.el7 lxc-templates.x86_64 0:1.0.11-2.el7 Dependency Installed: libtirpc.x86_64 0:0.2.4-0.16.el7 lua-alt-getopt.noarch 0:0.7.0-4.el7 lua-filesystem.x86_64 0:1.6.2-2.el7 lua-lxc.x86_64 0:1.0.11-2.el7 python3.x86_64 0:3.6.8-13.el7 python3-libs.x86_64 0:3.6.8-13.el7 python3-pip.noarch 0:9.0.3-7.el7_7 python3-setuptools.noarch 0:39.2.0-10.el7 python36-lxc.x86_64 0:1.0.11-2.el7 Complete! [root@lxc ~]#
提示：安裝前請配置好epel源，以及base源；
2、新增網橋
3、檢查當前系統是否滿足建立容器的條件
[root@lxc ~]# lxc-checkconfig Kernel configuration not found at /proc/config.gz; searching... Kernel configuration found at /boot/config-3.10.0-693.el7.x86_64 --- Namespaces --- Namespaces: enabled Utsname namespace: enabled Ipc namespace: enabled Pid namespace: enabled User namespace: enabled newuidmap is not installed newgidmap is not installed Network namespace: enabled Multiple /dev/pts instances: enabled --- Control groups --- Cgroup: enabled Cgroup clone_children flag: enabled Cgroup device: enabled Cgroup sched: enabled Cgroup cpu account: enabled Cgroup memory controller: enabled Cgroup cpuset: enabled --- Misc --- Veth pair device: enabled Macvlan: enabled Vlan: enabled Bridges: enabled Advanced netfilter: enabled CONFIG_NF_NAT_IPV4: enabled CONFIG_NF_NAT_IPV6: enabled CONFIG_IP_NF_TARGET_MASQUERADE: enabled CONFIG_IP6_NF_TARGET_MASQUERADE: enabled CONFIG_NETFILTER_XT_TARGET_CHECKSUM: enabled --- Checkpoint/Restore --- checkpoint restore: enabled CONFIG_FHANDLE: enabled CONFIG_EVENTFD: enabled CONFIG_EPOLL: enabled CONFIG_UNIX_DIAG: enabled CONFIG_INET_DIAG: enabled CONFIG_PACKET_DIAG: enabled CONFIG_NETLINK_DIAG: enabled File capabilities: enabled Note : Before booting a new kernel, you can check its configuration usage : CONFIG=/path/to/config /usr/bin/lxc-checkconfig [root@lxc ~]#
提示：如果沒有報error之類的就表示當前環境滿足建立容器的條件
4、指定模板建立容器
[root@lxc ~]# lxc-create -n test -t /usr/share/lxc/templates/lxc-centos
Host CPE ID from /etc/os-release: cpe:/o:centos:centos:7
Checking cache download in /var/cache/lxc/centos/x86_64/7/rootfs ...
Downloading CentOS minimal ...
Loaded plugins: fastestmirror
base | 3.6 kB 00:00:00
updates | 2.9 kB 00:00:00
Determining fastest mirrors
* base: mirrors.aliyun.com
* updates: mirrors.aliyun.com
Resolving Dependencies
--> Running transaction check
---> Package chkconfig.x86_64 0:1.7.4-1.el7 will be installed
--> Processing Dependency: rtld(GNU_HASH) for package: chkconfig-1.7.4-1.el7.x86_64
--> Processing Dependency: libpopt.so.0(LIBPOPT_0)(64bit) for package: chkconfig-1.7.4-1.el7.x86_64
--> Processing Dependency: libc.so.6(GLIBC_2.14)(64bit) for package: chkconfig-1.7.4-1.el7.x86_64
……省略部分內容
Container rootfs and config have been created.
Edit the config file to check/enable networking setup.
The temporary root password is stored in:
'/var/lib/lxc/test/tmp_root_pass'
The root password is set up as expired and will require it to be changed
at first login, which you should do as soon as possible. If you lose the
root password or wish to change it without starting the container, you
can change it from the host by running the following command (which will
also reset the expired flag):
chroot /var/lib/lxc/test/rootfs passwd
[root@lxc ~]#
提示：-t表示指定模板，該模板其實就是一shell指令碼，在安裝lxc-templates這個包後，預設/usr/share/lxc/templates/下面有幾個模板；如果能看到以上提示表示容器已經成功建立，我們可以使用lxc-ls檢視當前系統建立的所有容器；
[root@lxc ~]# lxc-ls test [root@lxc ~]#
提示：可以看到當前系統只有名為test的容器
5、修改當前test容器的root密碼
[root@lxc ~]# chroot /var/lib/lxc/test/rootfs passwd Changing password for user root. New password: BAD PASSWORD: The password is shorter than 8 characters Retype new password: passwd: all authentication tokens updated successfully. [root@lxc ~]#
提示：其實不用修改也行，預設的密碼存放在/var/lib/lxc/test/tmp_root_passwd這個檔案中；不修改密碼登入容器後，它會提示我們修改密碼
6、啟動容器，並登入容器
[root@lxc ~]# lxc-start -n test
systemd 219 running in system mode. (+PAM +AUDIT +SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 -SECCOMP +BLKID +ELFUTILS +KMOD +IDN)
Detected virtualization lxc.
Detected architecture x86-64.
Welcome to CentOS Linux 7 (Core)!
Running in a container, ignoring fstab device entry for /dev/root.
Cannot add dependency job for unit display-manager.service, ignoring: Unit not found.
[ OK ] Reached target Local Encrypted Volumes.
[ OK ] Reached target Swap.
[ OK ] Started Dispatch Password Requests to Console Directory Watch.
[ OK ] Started Forward Password Requests to Wall Directory Watch.
[ OK ] Reached target Paths.
[ OK ] Reached target Remote File Systems.
[ OK ] Created slice Root Slice.
[ OK ] Listening on Journal Socket.
[ OK ] Created slice User and Session Slice.
[ OK ] Listening on /dev/initctl Compatibility Named Pipe.
[ OK ] Listening on Delayed Shutdown Socket.
[ OK ] Created slice System Slice.
Mounting Huge Pages File System...
Starting Read and set NIS domainname from /etc/sysconfig/network...
Starting Journal Service...
Starting Remount Root and Kernel File Systems...
[ OK ] Reached target Slices.
[ OK ] Created slice system-getty.slice.
Mounting POSIX Message Queue File System...
[ OK ] Mounted Huge Pages File System.
[ OK ] Started Journal Service.
[ OK ] Started Read and set NIS domainname from /etc/sysconfig/network.
[ OK ] Mounted POSIX Message Queue File System.
[ OK ] Started Remount Root and Kernel File Systems.
Starting Configure read-only root support...
Starting Flush Journal to Persistent Storage...
Starting Rebuild Hardware Database...
[ OK ] Reached target Local File Systems (Pre).
<46>systemd-journald[16]: Received request to flush runtime journal from PID 1
[ OK ] Started Flush Journal to Persistent Storage.
[ OK ] Started Configure read-only root support.
Starting Load/Save Random Seed...
[ OK ] Reached target Local File Systems.
Starting Rebuild Journal Catalog...
Starting Create Volatile Files and Directories...
Starting Mark the need to relabel after reboot...
[ OK ] Started Load/Save Random Seed.
[ OK ] Started Rebuild Journal Catalog.
[ OK ] Started Create Volatile Files and Directories.
[ OK ] Started Mark the need to relabel after reboot.
Starting Update UTMP about System Boot/Shutdown...
[ OK ] Started Update UTMP about System Boot/Shutdown.
[ OK ] Started Rebuild Hardware Database.
Starting Update is Completed...
[ OK ] Started Update is Completed.
[ OK ] Reached target System Initialization.
[ OK ] Listening on D-Bus System Message Bus Socket.
[ OK ] Reached target Sockets.
[ OK ] Reached target Basic System.
Starting Permit User Sessions...
Starting OpenSSH Server Key Generation...
Starting LSB: Bring up/down networking...
[ OK ] Started D-Bus System Message Bus.
Starting Login Service...
[ OK ] Started Daily Cleanup of Temporary Directories.
[ OK ] Reached target Timers.
[ OK ] Started Permit User Sessions.
Starting Cleanup of Temporary Directories...
[ OK ] Started Console Getty.
[ OK ] Reached target Login Prompts.
[ OK ] Started Command Scheduler.
[ OK ] Started Cleanup of Temporary Directories.
[ OK ] Started Login Service.
[ OK ] Started OpenSSH Server Key Generation.
CentOS Linux 7 (Core)
Kernel 3.10.0-693.el7.x86_64 on an x86_64
test login: root
Password:
You are required to change your password immediately (root enforced)
Changing password for root.
(current) UNIX password:
New password:
Retype new password:
[root@test ~]# hostname
test
[root@test ~]#
提示：以上是啟動容器後，用預設密碼登入容器，它會提示我們修改密碼；如果想要讓該容器後臺執行（不佔據當前shell終端），可以使用-d選項指定即可；
檢視test容器的資訊
[root@lxc ~]# lxc-info -n test Name: test State: RUNNING PID: 5896 IP: 192.168.0.216 CPU use: 0.16 seconds BlkIO use: 0 bytes Memory use: 1.34 MiB KMem use: 0 bytes Link: veth6WQY6V TX bytes: 1.67 KiB RX bytes: 17.50 KiB Total bytes: 19.17 KiB [root@lxc ~]#
停止test容器
[root@lxc ~]# lxc-stop -n test [root@lxc ~]# lxc-info -n test Name: test State: STOPPED [root@lxc ~]#
銷燬容器
[root@lxc ~]# lxc-destroy -n test [root@lxc ~]# lxc-ls [root@lxc ~]#
提示：銷燬容器，容器的狀態必須是停止狀態，否則銷燬不了
以上就lxc容器的簡單管理；