# Compressing and archiving

## Compression types

It's to make data smaller and making it easier to transfer also keep the integrity

There are two types of compression: **lossy** and **lossless**

Basically lossy will not keep the integrity but make files significantly smaller compared to lossless, but it will ensure the integrity of the file and make it slightly smaller

## T-archiving

To compress files we should **archive** them in advance, in linux we can use `tar` command to achieve this.

Let’s say we have some files: `myscript.sh, mysecret.txt, mynotes.txt`

```bash
$ tar -cvf Packed.tar myscript.sh, mysecret.txt, mynotes.txt
 myscript.sh
 mysecret.txt
 mynotes.txt
```

Flags: `c` - create, `v` - verbose(optional), `f` - write to the file after the flag

```bash
$ tar -tvf Packed.tar
-rwxr-xr-x 1 vix vix 22311 Dec 1 2025 18:00 myscript.sh
-rw-r----- 1 vix vix 8791  Dec 1 2025 18:00 mysecret.txt
-rw-r----- 1 vix vix 3992  Dec 1 2025 18:01 mynotes.txt
```

Here we see another flg `t` we use tarball to list the file out without extracting them, if you want ot extract them add a `x` flag

```bash
$ tar -xvf Packed.tar 
 myscript.sh
 mysecret.txt
 mynotes.txt
```

## Compressing files

To compress the files we can use these:

| Tool  | Extensions    | Speed     | Compression Ratio |
| ----- | ------------- | --------- | ----------------- |
| gzip  | .tar.gz, .tgz | Fastest   | Good              |
| bzip2 | .tar.bz2      | Slow      | High              |
| xz    | .tar.xz       | Very Slow | Best              |
| zip   | .zip          | Fast      | Good              |

### gzip

```bash
$ gzip/bzip2/xz/zip/etc Packed.* #zip file
$ ls
 Packed.tar.(gz)
$ gunzip Packed.* #unzip file
```

## Creating Physical copies of storage devices

Here we will use `dd` command to make a bit-by-bit copy of a file, file system, or entire hard drive. (including deleted files)

It’s useful when need to do recovery or having backups

```bash
$ dd if=input_file of=output_file
```

Note that `dd` will copy the exact size as the input file


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