Remove old kernels on Linux

Display current kernel

  $ uname -r
  $ uname -mrs

On ubuntu

  • List all installed kernels 
    $ dpkg --list | grep linux-image
  • Remove old kernels 
    $ sudo apt-get autoremove
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Linux System Monitor Commands

Checking service/process

SERVICE=lighttpd
if ps ax | grep -v grep | grep $SERVICE > /dev/null; then echo -n "\"$SERVICE\" : \"running\","; else echo -n "\"$SERVICE\" : \"not running\","; fi
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Ubuntu proxy settings

For apt, software center etc

edit file /etc/apt/apt.conf

Acquire::http::proxy "http://username:password@host:port/";
Acquire::ftp::proxy "ftp://username:password@host:port/";
Acquire::https::proxy "https://username:password@host:port/";

Environment variables

edit file /etc/environment

http_proxy=http://username:password@host:port/
ftp_proxy=ftp://username:password@host:port/
https_proxy=https://username:password@host:port/
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Secure Docker using USER and Volume

Issue

Docker user has root privilege on host. The default user in container is root. In order to secure docker, we can create a user in docker container and run as non privilege user. The problem is that some services in docker need to write data to disk. E.g. druple has a files folder to store user uploaded files.

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Docker restart policies.

Policies:

  • no - this is defualt value
  • no-failure - restart container if it returns an error exit code. It also supports maximum numbers of times Docker will try.
  • unless-stopped - only restart container if it is running after reboot or restart docker service
  • always - Always keep the container running
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