一种docker debug 方式

Debug

查看指定 pod 运行在哪个宿主机上
kubctl describe pod <pod> -n mservice
获得容器的 pid
docker inspect -f {{.State.Pid}} <container>
进入该容器的 network namespace

nsenter --target 3326 --mount --uts --ipc --net --pid

可以使用各种命令进行debug

可以执行参数 -n 然后使用tcpdump抓包


nsenter使用

NSENTER(1)                                                            User Commands                                                            NSENTER(1)

NAME
       nsenter - run program with namespaces of other processes

SYNOPSIS
       nsenter [options] [program [arguments]]

DESCRIPTION
       Enters the namespaces of one or more other processes and then executes the specified program.  Enterable namespaces are:

       mount namespace
              Mounting  and unmounting filesystems will not affect the rest of the system (CLONE_NEWNS flag), except for filesystems which are explicitly
              marked as shared (with mount --make-shared; see /proc/self/mountinfo for the shared flag).

       UTS namespace
              Setting hostname or domainname will not affect the rest of the system.  (CLONE_NEWUTS flag)

       IPC namespace
              The process will have an independent namespace for System V message queues, semaphore sets and shared memory segments.  (CLONE_NEWIPC flag)

       network namespace
              The process will have independent IPv4 and IPv6 stacks, IP routing tables, firewall  rules,  the  /proc/net  and  /sys/class/net  directory
              trees, sockets, etc.  (CLONE_NEWNET flag)

       PID namespace
              Children will have a set of PID to process mappings separate from the nsenter process (CLONE_NEWPID flag).  nsenter will fork by default if
              changing the PID namespace, so that the new program and its children share the same PID namespace  and  are  visible  to  each  other.   If
              --no-fork is used, the new program will be exec'ed without forking.

       user namespace
              The process will have a distinct set of UIDs, GIDs and capabilities.  (CLONE_NEWUSER flag)

       See clone(2) for the exact semantics of the flags.

       If program is not given, then ``${SHELL}'' is run (default: /bin/sh).

OPTIONS
       -t, --target pid
              Specify a target process to get contexts from.  The paths to the contexts specified by pid are:

              /proc/pid/ns/mnt    the mount namespace
              /proc/pid/ns/uts    the UTS namespace
              /proc/pid/ns/ipc    the IPC namespace
              /proc/pid/ns/net    the network namespace
              /proc/pid/ns/pid    the PID namespace
              /proc/pid/ns/user   the user namespace
              /proc/pid/root      the root directory
              /proc/pid/cwd       the working directory respectively

       -m, --mount[=file]
              Enter  the  mount  namespace.   If  no file is specified, enter the mount namespace of the target process.  If file is specified, enter the
              mount namespace specified by file.

       -u, --uts[=file]
              Enter the UTS namespace.  If no file is specified, enter the UTS namespace of the target process.  If file  is  specified,  enter  the  UTS
              namespace specified by file.

       -i, --ipc[=file]
              Enter  the  IPC  namespace.   If  no file is specified, enter the IPC namespace of the target process.  If file is specified, enter the IPC
              namespace specified by file.

       -n, --net[=file]
              Enter the network namespace.  If no file is specified, enter the network namespace of the target process.  If file is specified, enter  the
              network namespace specified by file.

       -p, --pid[=file]
              Enter  the  PID  namespace.   If  no file is specified, enter the PID namespace of the target process.  If file is specified, enter the PID
              namespace specified by file.

       -U, --user[=file]
              Enter the user namespace.  If no file is specified, enter the user namespace of the target process.  If file is specified, enter  the  user
              namespace specified by file.  See also the --setuid and --setgid options.

       -G, --setgid gid
              Set  the  group  ID  which will be used in the entered namespace and drop supplementary groups.  nsenter(1) always sets GID for user names‐
              paces, the default is 0.

       -S, --setuid uid
              Set the user ID which will be used in the entered namespace.  nsenter(1) always sets UID for user namespaces, the default is 0.

       --preserve-credentials
              Don't modify UID and GID when enter user namespace. The default is to drops supplementary groups and sets GID and UID to 0.

       -r, --root[=directory]
              Set the root directory.  If no directory is specified, set the root directory to the root directory of the target process.  If directory is
              specified, set the root directory to the specified directory.

       -w, --wd[=directory]
              Set  the  working  directory.   If no directory is specified, set the working directory to the working directory of the target process.  If
              directory is specified, set the working directory to the specified directory.

       -F, --no-fork
              Do not fork before exec'ing the specified program.  By default, when entering a PID namespace, nsenter calls fork before  calling  exec  so
              that any children will also be in the newly entered PID namespace.

       -Z, --follow-context
              Set  the  SELinux  security  context  used for executing a new process according to already running process specified by --target PID. (The
              util-linux has to be compiled with SELinux support otherwise the option is unavailable.)

       -V, --version
              Display version information and exit.

       -h, --help
              Display help text and exit.

SEE ALSO
       setns(2), clone(2)

AUTHORS
       Eric Biederman ⟨[email protected]⟩
       Karel Zak ⟨[email protected]⟩

AVAILABILITY
       The nsenter command is part of the util-linux package and is  available  from  Linux  Kernel  Archive  ⟨ftp://ftp.kernel.org/pub/linux/utils/util-
       linux/⟩.