sysctl -asudo sysctl net.ipv4.ip_forward=1/etc/sysctl.conf and apply the configuration without a reboot using sysctl -p.htop is an interactive process viewer:
ps -l.
nice -n +20 top and sudo renice -n 0 1190 respectively.kill -l displays the signal types.
kill 1190 may be used to send a signal to a process ID, it uses the default signal SIGTERM that attempts to gracefully terminate a process. You may force a process to terminate using kill -9 1190.killall top may be used to send a signal to processes by name.jobs displays the status of running processes/ jobs.bg 1 or in the forground using fg 1. fg without a job number brings the most recent job to the foreground.systemctl.
systemctl list-units -t service display all active services.systemctl status ssh shows the status of a service including recent log information that may also be gathered using journalctl -u ssh.systemctl [start/stop] ssh and change the startup mode with systemctl [enable/disable] ssh.sudo crontab -u root -l may be used to view system-wide scheduled jobs for a user.crontab -e that will create a configuration file under /var/spool/cron/crontabs/rich.sudo apt update is used to download package information from sources configured in /etc/apt/source.list.d.apt search htop is used to search for available packages. Whereas apt list --installed shows the packages already installed.apt [install/remove/purge] htop.sudo apt install kubelet=1.25.5-00 and then prevent the package from being upgraded using sudo apt-mark hold kubelet.apt show htop displays verbose information about a package including dependencies.sudo apt upgrade can be used to upgrade existing packages, sudo apt dist-upgrade in addition upgrades the Kernel and adds/removes dependant packages automatically.sudo apt-get clean may be used to clear the apt cache to reclaim valuable diskspace.apt is a frontend to dpkg. dpkg -V htop is a useful command to verify package installation.dpkg -S pstree can be used to identify which package a command was installed from.snap that allows an application and its dependencies to be bundled together so that it works across Linux distros.snap find firefox.sudo snap [install/remove/refresh] firefox. If sudo snap refresh is run without specifying a package name all packages on the system are updated.lvdisplay.sudo mkdir /mnt/sysimage.sudo mount /dev/ubuntu-vg/ubuntu-lv /mnt/sysimagesudo chroot /mnt/sysimage.passwd root.emergency or single (and a space) to the kernel command that starts with linux respectively. Then F10 to boot.sudo fsck.ext4 /dev/sda1 may be used to run a filesystem check against an unmounted filesystem.sudo touch /forcefsck may be used to run a filesystem check against a mounted filesystem at the next reboot.fsck activity in /run/initramfs/fsck.log.virsh list may display running VMs.virsh [start/shutdown/suspend/resume] VM01 may be used to change the state of a Virtual Machine.sudo apt install docker.io
systemctl status docker
sudo usermod -aG docker rich Note: You will have to logoff and then back in again for the permission to take effect.docker search ubuntu. You can findout further information about an image by browsing dockerhub.docker pull ubuntu.docker images and obtain the IMAGE ID for subsequent commands.docker rmi 12a.docker commit c7 ubuntu/apache2:1.0. docker ps would be used to obtain the CONTAINER ID.
docker images will confirm that a new image has been created.docker run -dit -p 8081:80 ubuntu/apache2:1.0 /bin/bash.docker attach 7e, start apache2 /etc/init.d/apache2 start and then exit the interactive shell with Ctrl then press P followed by Q.curl http://localhost:8081.mkdir apache_custom.vi Dockerfile and add the following:
FROM ubuntu
MAINTAINER Rich <richard.b.j.hudson@gmail.com>
# Avoid confirmation messages
ARG DEBIAN_FRONTEND=noninteractive
# Update the container's packages
RUN apt update; apt dist-upgrade -y
# Install Apache and VIM
RUN apt install -y apache2 vim-nox
# Start Apache
ENTRYPOINT apachectl -D FOREGROUND
docker build -t ubuntu/apache_custom:1.0 .docker run -dit -p 8080:80 ubuntu/apache_custom:1.0docker run -it ubuntu /bin/bash.
docker ps or list all containers docker ps -all. This set of commands can be used to obtain the CONTAINER ID for use in subsequent commands.docker attach 3bdd9cd79b2a. If you exit the container shell the container will be stopped.docker [start/stop] 3bdd9cd79b2adocker rm 3bdd9cd79b2a. Note: The container has to be in a stopped state.docker run -dit -p 8080:80 ubuntu /bin/bash.
docker ps
docker attach f9
apt update
apt install apache2
/etc/init.d/apache2 start
Note: There is no init system inside a container so you cannot run systemctl commands.
curl http://localhost:8080.docker create -p 8080:80 ubuntu.sudo snap install lxd
snap list lxd
sudo usermod -aG lxd rich Note: You will have to logoff and then back in again for the permission to take effect.lxd init.lxc launch ubuntu:22.04 container01.
lxc image list, obtain the FINGERPRINT for further commands.lxc image delete 6d.lxc list, and obtain the container name for use with further commands.lxc [start/stop/delete] container01.lxc exec container01 bash.
lxc exec container01 -- su --login ubuntu.lxc config set container01 boot.autostart 1.lxc profile create bridge-profile.lxc profile edit bridge-profile - the configuration should look similar to below:
config: {}
description: Network Bridge Connection Profile
devices:
eth1:
name: eth1
nictype: bridged
parent: br0
type: nic
name: bridge-profile
used_by: []
lxc launch ubuntu:22.04 container02 -p default -p bridge-profile. Note: The default profile is loaded first, followed by the bridge-profile profile to ensure the latter overrides any conflicting settings. lxc exec container02 bash
apt install apache2
exit
lxc list and test connectivity curl http://192.168.101.112. Note: You can add a lxc profile to an existing container using lxc profile add container01 bridge-profile.sudo systemctl stop apparmor
sudo systemctl disable apparmor
sudo systemctl status apparmor
getenforce or sestatus. To use the tools you may need to install selinux-utils, policycoreutils and selinux-basics:
sudo apt install selinux-basics selinux-utils policycoreutils
sestatus will report disabled, enable SELinux using sudo selinux-activate and then reboot.sudo setenforce [Enforcing/ Permissive], it will default to Permissive after SELinux has been enabled.sudo vi /etc/selinux/config and adding:
SELINUX=disabled
-Z option often works with existing commands to display context/ labels, for example ps axZ | grep apache2 and ls -Z /var/www/html shows that the apache2 process runs in the context of httpd_t which is why it is allowed to access the files with a label of httpd_sys_content_t.semanage fcontext -a -t httpd_sys_content_t /var/www/html.
cd /var/www/html
sudo sh -c "echo file 1 > ./file1.html"
sudo setenforce Enforcing
curl http://localhost/file1.html
sudo sh -c "echo file2 >/root/file2.html"
sudo mv /root/file2.html /var/www/html
sudo setenforce Enforcing
curl http://localhost/file2.html
sudo chcon -t httpd_sys_content_t file2.html
curl http://localhost/file2.html
sudo restorecon -RFv /var/www/html.