DevMemo – linux

Blog: How To Debug Emacs Cpp Indentation

Sat, 26 Aug 2023 21:16:11 +0000

Do Syntactic Analysis

Do c-show-syntactic-information or C-c C-s to get an syntactic analysis first, you should get something like this

Syntactic analysis: ((statement-block-intro 930))

At the same time, emacs will also highlight the anchor point.

Set `c-set-offset`

Do the following to adjust the indentation.

(defun c-indentation-hook ()
 (c-set-offset 'statement-block-intro 2)
)

(add-hook 'c-mode-common-hook 'c-indentation-hook)

You’ll need to reopen the file to allow the above change to take effect.

Blog: Automate Ubuntu Installation

Wed, 01 Feb 2023 16:22:53 -0800

As a software engineer, I frequently needed to create new Linux VMs for testing and other purposes. The traditional way of installing Linux on a VM is very inefficient, which consumes a lot of my time. Automating the process is very appealing to me.

In this post, I’m going to give you step-by-step instructions of how to do that.

Build Ubuntu Auto-Install Iso Image

Prerequisites

To build an auto-install ubuntu image, we’ll need to install the following packages first

sudo apt update && sudo apt install p7zip wget xorriso whois

Set Up Build Environment

Next, let’s download the latest ubuntu image from the official website. The version we are going to be using is ubuntu 20.04.

# Go to your home directory.
cd

# Create a directory for our image building process.
mkdir ubuntu-auto-install-image-building
cd ubuntu-auto-install-image-building/

# Download the latest package.
wget https://releases.ubuntu.com/22.04.1/ubuntu-22.04.1-live-server-amd64.iso

# Create a source directory.
mkdir ubuntu-iso-sources

# Unpack the iso to the ubuntu-iso-sources dir.
7z -y x ubuntu-22.04.1-live-server-amd64.iso -oubuntu-iso-sources

# Go into the source directory.
cd ubuntu-iso-sources

# Move BOOT directory outside, since this is not needed in the final iso.
mv \[BOOT\] ../BOOT

Update Image Files

After the source files are unpacked, let’s update some files.

Create An Grub Entry

The first file to update is the grub file, i.e., ~/ubuntu-auto-install-image-building/ubuntu-iso-sources/boot/grub/grub.cfg. We’ll need to do two things:

Add an autoinstall entry.
Make wait time shorter (this is optional).

The updated file looks like this. The highlighted lines are modified.

set timeout=5

loadfont unicode

set menu_color_normal=white/black
set menu_color_highlight=black/light-gray

menuentry "Autoinstall Ubuntu Server" {
 set gfxpayload=keep
 linux /casper/vmlinuz quiet autoinstall ds=nocloud\;s=/cdrom/server/ ---
 initrd /casper/initrd
}

menuentry "Try or Install Ubuntu Server" {
 set gfxpayload=keep
 linux /casper/vmlinuz ---
 initrd /casper/initrd
}
grub_platform
if [ "$grub_platform" = "efi" ]; then
menuentry 'Boot from next volume' {
 exit 1
}
menuentry 'UEFI Firmware Settings' {
 fwsetup
}
else
menuentry 'Test memory' {
 linux16 /boot/memtest86+.bin
}
fi

Create File user-data

Next, we’ll need to create a user-data file, ~/ubuntu-auto-install-image-building/ubuntu-iso-sources/server/user-data, with the following content.

#cloud-config
autoinstall:
 version: 1
 keyboard:
 layout: us
 identity:
 hostname: ubuntu-server
 password: "$y$j9T$qiKEYsg5oLCDV.XxExdEB/$41TEJJWV7he/aTyHQEDAWJyfKceDtCYVk.Agh9aAvk3"
 username: swe
 ssh:
 allow-pw: true
 install-server: true

This is a minimum setup, which only creates a user with a password. The password is devmemo-passwd. The password string above is generated using the following command

mkpasswd "devmemo-passwd"

Note that the above config is really a minimum one. Check out this page if you need more configurations.

Create File meta-data

For our use case, we don’t need any data in meta-data file. So we’ll just need to create an empty file.

touch ~/ubuntu-auto-install-image-building/ubuntu-iso-sources/server/meta-data

Create An Auto-Installation Iso Image

# Create the auto-installation iso image.
xorriso -as mkisofs -r \
 -V 'Ubuntu 22.04 LTS (Auto Install)' \
 -o ../ubuntu-22.04-autoinstall.iso \
 --grub2-mbr ../BOOT/1-Boot-NoEmul.img \
 -partition_offset 16 \
 --mbr-force-bootable \
 -append_partition 2 28732ac11ff8d211ba4b00a0c93ec93b ../BOOT/2-Boot-NoEmul.img \
 -appended_part_as_gpt \
 -iso_mbr_part_type a2a0d0ebe5b9334487c068b6b72699c7 \
 -c '/boot.catalog' \
 -b '/boot/grub/i386-pc/eltorito.img' \
 -no-emul-boot -boot-load-size 4 -boot-info-table --grub2-boot-info \
 -eltorito-alt-boot \
 -e '--interval:appended_partition_2:::' \
 -no-emul-boot .

# Check out the image.
cd ..
ls -alh ubuntu-22.04-autoinstall.iso

Now the ubuntu auto-install image is created. You can use it to auto install ubuntu on physical machines or VMs.

Create Your VMs

After you finish the last section, you already have an ubuntu auto-installation image. This section is totally optional.

In this section, I’ll demonstrate how to use this image on proxmox.

Upload The Image To Proxmox Host

First, let’s upload the image to the VM host. You can either use the web UI, or directly copy the iso into /var/lib/vz/template/iso.

Create A VM

Next, let’s create a VM, put the iso into its cdrom, and make the cdrom the boot device.

qm create 1000 --name vm1000 --cores 4 --memory 8192 \
 --scsi0 file=ssd:32 --net0 virtio,bridge=vmbr0 \
 --cdrom local:iso/ubuntu-22.04-autoinstall.iso

For example, the above command will create a 4 core, 8GB ram, and 32GB ssd VM. Start the VM, and then all you have to do is to wait until the OS is fully installed.

Cheatsheets: Linux Cheatsheet

Mon, 01 Jan 0001 00:00:00 +0000

Commands

File & Directory Basics

# List files in the current directory.
ls

# List files in the current directory with details.
ls -alh

# Change current directory.
cd

# Show current directory.
pwd

# Create an empty directory.
mkdir

# Copy file.
cp <src-filename> <dst-filename>

# Copy directory.
cp -Rf <src-dirname> <dst-dirname>

# Move file or directory.
mv <src-filename> <dst-filename>

# Remove file.
rm <filename>

# Remove an empty directory.
rmdir <dirname>

# Remove a non-empty directory.
rm -Rf <dirname>

# Create a new empty file.
touch <filename>

# Find files.
find . -iname <filename-regex>

# Find all files.
find . -type f

File Content

# Print file content.
cat <filename>

# Search texts in file.
grep <text> <filename>

# Search regex pattern in file.
grep -e <regex-pattern> <filename>

# Show first few lines in file.
head -n <line-count> <filename>

# Show last few lines in file.
tail -n <line-count> <filename>

# Follow file changes.
tail -f <filename>

File Access

# Change file access. An example of access-code is 600.
chmod <access-code> <filename>

# Change file owner.
chown <owner>[:<group>] <filename>

Package & Compress

# Pack a directory into a tar file.
tar -cvf <tar-filename>.tar <dirname>

# Unpack a tar file.
tar -xvf <tar-filename>.tar

# Zip a file.
zip <zip-filename> file1 file2 file3 ...

# Unzip a file.
unzip <zip-filename>

Disk

# Show free disk spaces for each block device.
df -alh

# Display the disk usage of files under the current directory.
du -h ./*

# Show block devices.
lsblk

Process

# List process.
ps aux

# Kill a process with SIGTERM.
kill <pid>

# Kill a process with SIGKILL (the strongest killing signal).
kill -9 <pid>

# List all processes in a terminal UI.
top

# List all processes in an advanced terminal UI.
htop

Networking

# Download data from url.
curl <url>

# Download data from url to local file.
curl <url> -o <filename>

# List all ports opened.
netstat -an

# List network configuration.
ifconfig

# Ping network connectivity.
ping

User

# Add a new user.
sudo adduser <username>

# Delete a user.
sudo deluser <username>

Packages

# Install packages on ubuntu or debian.
sudo apt install <package-name>[=<version>]

# Uninstall packages from ubuntu or debian.
sudo apt-get --purge remove <package-name>

System

# Display information about your system.
uname -a

# Display Linux release information
lsb_release -a

# Show hostname.
hostname

# Reboot system now.
sudo reboot now

# Shutdown system now.
sudo shutdown -h now

Services

# List all units.
systemctl list-units

# List all service units.
systemctl list-units --type=service

# Start a service.
sudo systemctl start <service-name>

# Restart a service.
sudo systemctl restart <service-name>

# Stop a service.
sudo systemctl stop <service-name>

# Check a service status.
sudo systemctl status <service-name>

# Enable a service to start as system starts.
sudo systemctl enable <service-name>

Configuration Files

File Path	Scope	File Use
`/boot/grub/grub.cfg`	global	the generated grub file
`/etc/bash.bashrc`	global	global config file for bash
`/etc/default/grub`	global	config used by update-grub to generate /boot/grub/grub.cfg
`/etc/dhcp/dhclient.conf`	global	DCHP client configs
`/etc/fstab`	global	startup mount configs
`/etc/hostname`	global	hostname
`/etc/hosts`	global	static dhcp entries
`/etc/mime.types`	global	MIME types and filename extensions associated with them
`/etc/motd`	global	log in prompt message
`/etc/profile`	global	commands for the login shell to execute
`/etc/resolv.conf`	global	DNS server config
`/etc/sudoers`	global	configs for sudoers
`/etc/timezone`	global	local timezone
`~/.bashrc`	user	bash startup config for non-login shell
`~/.editor`	user	sets the default editor for the user
`~/.gitconfig`	user	sets the default configs for git
`~/.profile`	user	shell startup commands
`~/.ssh/config`	user	user ssh config
`~/.vimrc`	user	vim config
`~/.emacs`	user	emacs config
`~/.xinitrc`	user	xmanager config