docker attach命令

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docker attach命令可以将当前终端的标准输入、标准输出和标准错误连接到指定的容器中，这允许操作者查看其正在进行的输出或交互式地控制它，就像命令直接在终端中运行一样。

  • 该命令显示的是容器 ENTRYPOINT/CMD 进程的输出, 执行该命令时有可能看起来像是hang住了，但是实际上进程可能没有与终端进行交互(输入内容到终端)。

  • 可以在docker的宿主机不同session中同时执行多次attach命令。

退出attach方式

CRTL+p CTRL+q 方式

ctrl+p ctrl+q是默认的detach键序列(key sequence)，也可以通过--detach-keys string来覆盖默认的键序列。自定义的string可以是[a-Z]的字母或ctrl-与以下内容的任意组合:

  • a-z (小写字母)

  • @

  • [

  • \

  • _

  • ^

这种方式要求容器运行(docker run)时必须同时指定 -i -t 参数。采用这种方式只是从容器中detach出来，不会停止容器的运行。

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########## session 1 ##########
[root@localhost ~]# docker run -it centos:8 /bin/bash --login
[root@a58c215443bd /]# ps -ef
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  2 11:21 pts/0    00:00:00 /bin/bash --login
root        18     1  0 11:21 pts/0    00:00:00 ps -ef
[root@a58c215443bd /]#

########## session 2 ##########
[root@localhost ~]# docker ps
CONTAINER ID    IMAGE       COMMAND               CREATED           STATUS          PORTS       NAMES
a58c215443bd    centos:8    "/bin/bash --login"   13 seconds ago    Up 10 seconds               epic_haslett
[root@localhost ~]# docker attach a58c
[root@a58c215443bd /]# [ctrl+p ctrl+q] read escape sequence
[root@localhost ~]# docker ps
CONTAINER ID    IMAGE       COMMAND               CREATED           STATUS          PORTS       NAMES
a58c215443bd    centos:8    "/bin/bash --login"   56 seconds ago    Up 52 seconds               epic_haslett
[root@localhost ~]#

如果容器运行时未同时指定 -i -t 参数，CTRL+p CTRL+q 无效。

CTRL+c方式

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--sig-proxy=true|false # 默认值 true
   Proxy all received signals to the process (non-TTY mode only). SIGCHLD, SIGKILL, and SIGSTOP are not proxied.

该选项仅在non-TTY模式下起作用，即docker run时不指定-t选项。此时，默认–sig-proxy为true，SIGINT信号被发送至docker中PID为1的进程。

CTRL+c 发送 SIGKILL 信号到容器。If –sig-proxy is true (the default),CTRL-c sends a SIGINT to the container

在容器中以PID 1运行的进程会被Linux特别处理:它会忽略任何带有默认操作的信号。因此，除非进行了相应的编码，否则进程不会在SIGINT或SIGTERM上终止。

–sig-proxy=true && docker run -it

交互式启动bash CTRL+C作用在attach的bash，对容器退出无效，在attach中输入exit时容器退出

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########## 交互式启动bash时 session 1
[root@localhost ~]# docker run -it centos:8 /bin/bash --login
WARNING: IPv4 forwarding is disabled. Networking will not work.
[root@b9c822d1b3eb /]#

########## session 2
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE        COMMAND               CREATED             STATUS         PORTS      NAMES
b9c822d1b3eb        centos:8     "/bin/bash --login"   46 seconds ago      Up 44 seconds             sleepy_kepler
[root@localhost ~]# docker attach b9c
[root@b9c822d1b3eb /]# ^C
[root@b9c822d1b3eb /]# exit
logout
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE      COMMAND      CREATED             STATUS              PORTS               NAMES
[root@localhost ~]#

交互式启动非bash时 CTRL+C对容器退出有效

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########## session 1
[root@localhost ~]# docker run -it centos:8 top -b
top - 12:46:53 up  4:28,  0 users,  load average: 1.76, 1.75, 1.84
Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
%Cpu(s): 60.0 us, 40.0 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :    991.2 total,    145.6 free,    466.6 used,    379.1 buff/cache
MiB Swap:   1024.0 total,    841.5 free,    182.5 used.    383.2 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
    1 root      20   0   48264   1980   1464 R  20.0   0.2   0:00.05 top

########## session 2
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE          COMMAND         CREATED             STATUS           PORTS      NAMES
0fb225d37701        centos:8       "top -b"        23 seconds ago      Up 20 seconds               confident_turing
[root@localhost ~]# docker attach 0fb
top - 12:47:25 up  4:28,  0 users,  load average: 2.22, 1.86, 1.88
Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
%Cpu(s): 39.5 us, 42.0 sy,  0.0 ni, 16.6 id,  0.0 wa,  0.0 hi,  1.9 si,  0.0 st
MiB Mem :    991.2 total,    146.1 free,    465.8 used,    379.3 buff/cache
MiB Swap:   1024.0 total,    841.5 free,    182.5 used.    384.0 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
    1 root      20   0   48264   1980   1464 R   0.0   0.2   0:00.06 top

top - 12:47:25 up  4:28,  0 users,  load average: 2.22, 1.86, 1.88
Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
%Cpu(s): 66.7 us, 33.3 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :    991.2 total,    146.1 free,    465.8 used,    379.3 buff/cache
MiB Swap:   1024.0 total,    841.5 free,    182.5 used.    384.0 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
    1 root      20   0   48264   1980   1464 R   0.0   0.2   0:00.06 top^C
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE        COMMAND             CREATED             STATUS      PORTS      NAMES
[root@localhost ~]#

–sig-proxy=true && docker run -d

交互式启动非bash时 CTRL+C对容器退出有效

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[root@localhost ~]# docker run -d centos:8 top -b
645242bbe8be193008f3794b4d9eb5dd88274da8b6b882743ec1c3c232d96a59
[root@localhost ~]#
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE          COMMAND             CREATED             STATUS          PORTS        NAMES
645242bbe8be        centos:8       "top -b"            6 seconds ago       Up 4 seconds                 happy_moser
[root@localhost ~]# docker attach 645
top - 12:52:15 up  4:33,  0 users,  load average: 2.04, 1.93, 1.89
Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
%Cpu(s): 22.7 us, 29.5 sy,  0.0 ni, 46.0 id,  0.0 wa,  0.0 hi,  1.8 si,  0.0 st
MiB Mem :    991.2 total,    143.9 free,    465.4 used,    381.9 buff/cache
MiB Swap:   1024.0 total,    841.5 free,    182.5 used.    384.3 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
    1 root      20   0   48264   1976   1464 R   0.3   0.2   0:00.07 top^C
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE           COMMAND             CREATED         STATUS              PORTS        NAMES
[root@localhost ~]#

–sig-proxy=false && docker run -it

交互式启动bash时 CTRL+C对容器退出无效，在attach中输入exit时容器退出

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########## session 1
[root@localhost ~]# docker run -it centos:8 /bin/bash --login
WARNING: IPv4 forwarding is disabled. Networking will not work.
[root@308cd9572fe2 /]#

########## session 2
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE         COMMAND               CREATED             STATUS         PORTS        NAMES
308cd9572fe2        centos:8      "/bin/bash --login"   7 seconds ago       Up 6 seconds                elated_tharp
[root@localhost ~]# docker attach --sig-proxy=false 308
[root@308cd9572fe2 /]# ^C
[root@308cd9572fe2 /]# exit
logout
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE         COMMAND             CREATED             STATUS              PORTS      NAMES
[root@localhost ~]#

–sig-proxy=false && docker run -d

交互式启动非bash时 CTRL+C对容器退出无效

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[root@localhost ~]# docker run -d centos:8 top -b
5cb4252610b412f1301b6d1561d3958edd79da20a22dbb65b8697ec5361ee25a
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE          COMMAND             CREATED             STATUS        PORTS     NAMES
5cb4252610b4        centos:8       "top -b"            7 seconds ago       Up 6 seconds            focused_perlman
[root@localhost ~]# docker attach --sig-proxy=false 5cb
top - 12:26:40 up  4:07,  0 users,  load average: 2.61, 2.24, 2.05
Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
%Cpu(s): 23.2 us, 30.5 sy,  0.0 ni, 44.2 id,  0.0 wa,  0.0 hi,  2.1 si,  0.0 st
MiB Mem :    991.2 total,    140.7 free,    465.7 used,    384.7 buff/cache
MiB Swap:   1024.0 total,    843.2 free,    180.8 used.    384.2 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
    1 root      20   0   48264   1980   1464 R   0.3   0.2   0:00.07 top^C
[root@localhost ~]# docker ps
CONTAINER ID        IMAGE          COMMAND             CREATED             STATUS         PORTS     NAMES