docker_under_the_hood

# To check the memory limit enforced via cgroup

# cat /sys/fs/cgroup/memory/memory.limit_in_bytes
536870912

OR

# docker container stats <container id>


# --pid let the container see the host process table(!!! carefull)
# Normal container run
$ docker container run -it centos bash

[root@83a91f678bd2 /]# ps -ef
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 14:45 pts/0    00:00:00 bash
root        14     1  0 14:46 pts/0    00:00:00 ps -ef

# Put the command in the background

$ vim /tmp/testfile&

# Let you see the host process table
docker container run -it --pid=host centos bash

# -v let you mount, the file on host to the mount point inside the container

$ docker container run -it -v /:/host --privileged centos bash

# --net=host open all network interface on the host to the container

docker container run -it --net=host centos bash

# --privileges open root and selinux priviledge on the container



# Check the logging driver

$ docker info |grep -i log
 Logging Driver: json-file
 Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 
 # To change the logging driver
 
 $ docker container run --log-driver none -dt centos ping google.com
 
# docker logs file is not available for drivers other then json-file and journald 

# To check if debug mode is enabled in docker
$ docker info |grep -i debug
 Debug Mode: false
 Debug Mode: false

# To enable debug mode
cat /etc/docker/daemon.json
 {
 "debug": true
 }
 
 # To verify it
 journalctl -u docker.service | tail