Cross-Compilation Overview

Cross-compilation involves building executables on a high-performance host architecture (like x86) to run on a different target architecture (like ARM). This approach leverages the host's superior resources and tooling, streamlining the development process before deployment to resource-constrained embedded devices.

Command Reference

1. apt

Advanced Package Tool (apt) serves as the primary package management front-end for Debian-based distributions. It simplifies software retrieval, installation, upgrades, and removal. Administrative privileges are mandatory for operations that modify the system state.

apt [options] [command] [package ...]

Frequently utilized operations include updating the local package index, upgrading installed software, and managing dependencies.

sudo apt update                # Synchronize package index files
sudo apt upgrade               # Install available upgrades
apt list --upgradeable         # Show packages with available updates
apt list --installed           # Display all installed packages
sudo apt full-upgrade          # Perform a full system upgrade, handling dependency changes
sudo apt install vim wget      # Install multiple packages
sudo apt show nginx            # Retrieve detailed package metadata
sudo apt remove vim            # Uninstall a package
sudo apt autoremove            # Purge orphaned dependencies
sudo apt purge wget            # Remove package along with configuration files
sudo apt search text-editor    # Search the repository for packages

2. dmesg

The dmesg utility reads or controls the kernel ring buffer. Boot-time messages and hardware detection logs are stored here, making it invaluable for troubleshooting kernel and driver issues.

dmesg [options]

dmesg                       # Print all kernel log messages
dmesg > kernel_logs.txt     # Redirect logs to a file for analysis
dmesg -C                    # Clear the ring buffer (useful before reproducing driver bugs)

3. dpkg-deb

This tool manipulates Debian archive (.deb) files. It allows developers to extract, inspect, and build Debian packages without installing them.

dpkg-deb [option...] command

Key actions include extracting control information and unpacking the payload.

dpkg-deb -x custom-pkg_1.0_arm64.deb ./dest_dir    # Extract package files to a directory
dpkg-deb -e custom-pkg_1.0_arm64.deb ./dest_dir/DEBIAN  # Extract control files
dpkg-deb -c custom-pkg_1.0_arm64.deb               # List contents of the archive

4. dpkg

Acting as the underlying engine for apt, dpkg installs, removes, and provides information about individual .deb packages. It operates at a lower level and does not automatically resolve dependencies.

dpkg [option...] command

dpkg -i package.deb      # Install a local .deb file
dpkg -r packagename      # Remove an installed package
dpkg -P packagename      # Purge package along with configuration files
dpkg -L packagename      # List files installed to your system from the package
dpkg -l packagename      # Display package status and version
dpkg -S /usr/bin/binary  # Find which package owns a specific file
dpkg -l                  # List all installed packages
dpkg -c package.deb      # List contents of an uninstalled .deb file
dpkg --configure packagename # Perform package configuration

5. find

The find command recursively traverses a directory hierarchy based on criteria such as name, size, modification time, or permissions.

find [path...] [expression]

Expressions can combine file attributes and logical operators for complex searches.

find . -name "document.md"                         # Locate a specific file by name
find /var/log -name "*.log"                        # Find all log files
find . -iname "*.Py"                               # Case-insensitive name search
find . -type d                                     # List only directories
find /home -user admin                             # Find files owned by admin
find . -type f -size +10M                          # Locate files larger than 10 Megabytes
find /tmp -mtime +7                                # Files modified more than 7 days ago
find . -ctime -3                                   # Files with status changed in the last 3 days
find /var/log -type f -mtime +7 -exec rm {} \;     # Delete old log files interactively
find . -type f -perm 755 -exec ls -l {} \;         # List files with exact 755 permissions
find . \( -name "*.jpg" -o -name "*.png" \)        # Search for multiple extensions
find . ! -name "*.tmp"                             # Exclude files ending in .tmp
find . -maxdepth 2 -name "*.conf"                  # Limit directory traversal depth
find . -type f -empty                              # Locate zero-length files

6. ifconfig

While largely superseded by the ip command, ifconfig remains widely used for configuring and querying network interface parameters like IP addresses, netmasks, and hardware addresses.

ifconfig [-a] [-v] [-s] <interface> [[<AF>] <address>] ...

ifconfig                                         # Display active interfaces
ifconfig -a                                      # Show all interfaces, including disabled ones
ifconfig enp3s0                                  # Inspect a specific interface
ifconfig enp3s0 up                               # Enable the interface
ifconfig enp3s0 down                             # Disable the interface
ifconfig enp3s0 10.0.0.15                        # Assign an IPv4 address
ifconfig enp3s0 10.0.0.15 netmask 255.255.255.0  # Assign IP and netmask
ifconfig enp3s0 hw ether 00:11:22:33:44:55       # Modify the MAC address

7. ip

The ip command is the modern, feature-rich replacement for ifconfig, designed to manage routing, network devices, interfaces, and tunnels.

ip [ OPTIONS ] OBJECT { COMMAND | help }

ip link show                                     # Display all network interfaces
ip link set enp3s0 up                            # Bring an interface online
ip link set enp3s0 down                          # Take an interface offline
ip link set enp3s0 mtu 1400                      # Adjust the Maximum Transmission Unit
ip addr show                                     # List IP addresses associated with interfaces
ip addr add 10.0.0.15/24 dev enp3s0              # Add an IP address to an interface
ip addr del 10.0.0.15/24 dev enp3s0              # Remove an IP address
ip route show                                    # Display the routing table
ip route add 192.168.50.0/24 via 10.0.0.1        # Add a static route
ip route add default via 10.0.0.1                # Set the default gateway
ip route del 192.168.50.0/24                     # Delete a route

8. mount

Mount attaches a filesystem found on a device to the global file hierarchy at a specified mount point.

mount [-fnrsvw] [-t fstype] [-o options] device dir

mount /dev/sda1 /mnt/data                        # Attach a disk partition
mount -o ro /dev/sda1 /mnt/data                  # Mount as read-only
mount -o remount,rw /                            # Remount the root filesystem as read-write
mount -t nfs -o nolock 10.0.0.20:/export /mnt/nfs # Mount an NFS share

9. ssh

Secure Shell (ssh) establishes encrypted remote login sessions and enables command execution on distant machines.

ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-l login_name] destination [command]

ssh admin@10.0.0.20                              # Connect to a remote host
ssh -p 2222 admin@10.0.0.20                      # Specify a non-default port
ssh -i ~/.ssh/id_rsa admin@10.0.0.20             # Authenticate using a specific private key
ssh admin@10.0.0.20 "uname -a"                   # Execute a command remotely
ssh -L 8080:localhost:80 admin@10.0.0.20         # Create a local port forward

10. tar

tar archives multiple files into a single tarball, often paired with compression utilities like gzip or bzip2. It is essential for backups and software distribution.

tar [OPTION...] [FILE]...

tar -czvf project.tar.gz /home/admin/project      # Create a gzip-compressed archive
tar -cjvf archive.tar.bz2 documents/              # Create a bzip2-compressed archive
tar -tzvf project.tar.gz                          # List contents of a gzip archive
tar -xzvf project.tar.gz                          # Extract a gzip archive into the current directory
tar -xzvf project.tar.gz -C /opt/target/          # Extract to a specific directory

11. top

top provides a dynamic, real-time view of running system processes, CPU utilization, and memory consumption.

top -hv | -bcEHiOSs1 -d secs -n max -u|U user -p pid(s)

Interactive commands allow process manipulation while top is running. Press 'k' to kill a process, 'M' to sort by memory usage, or 'P' to sort by CPU usage.

top                                              # Launch the default system monitor
top -c                                           # Display absolute command paths
top -u admin                                     # Show processes owned by a specific user
top -p 1024,2048                                 # Monitor specific PIDs
top -d 2                                         # Set the refresh interval to 2 seconds
top -n 5                                         # Limit iterations before exiting

12. zip

zip compresses files into a ZIP archive, maintaining compatibility across various operating systems.

zip [-options] [-b path] [-t mmddyyyy] [-n suffixes] [zipfile list] [-xi list]

zip -r archive.zip /var/www/html                 # Recursively compress a directory
zip -r archive.zip *                             # Compress all items in the current directory
zip -d archive.zip unwanted.txt                  # Delete a file from the archive
zip -u archive.zip updated.txt                   # Update or add files to the archive