# Debian Package Manager

`apt` (Advanced Package Tool) is the standard Debian/Ubuntu package manager. It manages `.deb` files and their dependencies.

## Basic Commands

Update package lists from repositories:

```bash
sudo apt update
```

Install a package:

```bash
sudo apt install package-name
```

Remove package but keep config:

```bash
sudo apt remove package-name
```

Remove package and config files:

```bash
sudo apt purge package-name
```

Upgrade installed packages:

```bash
sudo apt upgrade
```

Upgrade including dependency changes (riskier):

```bash
sudo apt full-upgrade
```

## Searching

Find packages:

```bash
apt search keyword
apt search --names-only keyword
```

Show package details:

```bash
apt show package-name
```

## Low-Level Package Info

List installed packages:

```bash
dpkg -l
dpkg -l | grep keyword
```

List files in a package:

```bash
dpkg -L package-name
```

Check if package is installed:

```bash
dpkg -l package-name
```

## Repository Management

`apt-get` is the older CLI with identical functionality:

```bash
apt-get update
apt-get install package-name
```

Prefer `apt` for interactive use; `apt-get` for scripts (stable interface).

## Tips

- Always run `sudo apt update` before installing to ensure fresh metadata
- Use `sudo apt autoremove` to clean up unused dependencies
- `sudo apt-cache search` is equivalent to `apt search`
- Check for broken packages: `sudo apt check`
- Hold a package from upgrades: `sudo apt-mark hold package-name`
- Unhold: `sudo apt-mark unhold package-name`

`apt` is wrapper around `dpkg` (lower-level) and `apt-cache` (search). For most purposes, `apt` is sufficient.