Gist for CN101 1

## Get Docker Image
btrfs subvol create images/alpine
CID=$(docker run -d python:3.8-alpine true)
docker export $CID | tar -C images/alpine/ -xf-
btrfs subvol snapshot images/alpine/ containers/springrain
touch containers/springrain/I_AM_HERE


## tmux as a container and mount 
tmux
unshare --mount --uts --ipc --net --pid --fork bash
hostname springrain
exec bash
ps aux
strace ps aux


### 
mount -t proc proc /proc
ps aux

### 
mount --bind /fundocker/containers/springrain /fundocker/containers/springrain
mkdir /fundocker/containers/springrain/oldroot
cd /fundocker/containers/springrain/
pivot_root . oldroot
ps aux
mount -t proc proc /proc
mount | head
umount -l /oldroot

## networking
CPID=$(pidof unshare)
echo $CPID
ip link add name h$CPID type veth peer name c$CPID
ip link set c$CPID netns $CPID
ip link set h$CPID master docker0 up


export CPID=11716
ip link set lo up
ip link set  name eth0 up
ip addr add 172.17.42.3/16 dev eth0
ip route add default via 172.17.0.1

## cgroup
bin/cat <<EOF > ./test.py
a = ''
i=0
while True:
  i += 1
  print("%dmb" % (i*10,))
  some_str = ' ' * 10000000
  a = a + some_str
EOF
mkdir /sys/fs/cgroup/memory/mygroup
echo "100000000" > /sys/fs/cgroup/memory/mygroup/memory.limit_in_bytes
mkdir /sys/fs/cgroup/cpu/mycpugroup
sudo echo '5000' > /sys/fs/cgroup/cpu/mycpugroup/cpu.cfs_quota_us
cgexec -g cpu:mycpugroup ./test



```
#include <unistd.h>
#include <stdio.h>
#include <cstring>
#include <thread>

void test_cpu() {
    printf("thread: test_cpu start\n");
    int total = 0;
    while (1) {
        ++total;
    }
}

void test_mem() {
    printf("thread: test_mem start\n");
    int step = 20;
    int size = 10 * 1024 * 1024; // 10Mb
    for (int i = 0; i < step; ++i) {
        char* tmp = new char[size];
        memset(tmp, i, size);
        sleep(1);
    }
    printf("thread: test_mem done\n");
}

int main(int argc, char** argv) {
    std::thread t1(test_cpu);
    std::thread t2(test_mem);
    t1.join();
    t2.join();
    return 0;
}
```

### K3S
alias kubectl='k3s kubectl'
kubectl get nodes
kubectl create deployment hello-node --image=jmalloc/echo-server:latest