Everything eventually runs out, including computer memory. No matter how big your hard drive is, there will come a time when you won’t be able to write a new program or data to it. One way to save memory on your disks is to use archiving software, which “compresses” (packages) files. How the Astra Linux operating system archiver works, we tell you in this material based on the “Astra Linux” manual of the same name.
Compression
Information is compressed by replacing repetitive fragments with shorter records. Here is a simple example. Here is an example of a word separated by 5 spaces:
LONGEST COUNTRY
This string can be made shorter in machine memory:
LLI2NOSH3E5 COUNTRY
A number in a string means how many times the character that follows it is repeated. The result is that instead of 21 bytes, the string takes up 17 bytes. By simple calculation you can check that the compression of information in this case is 19% of the original volume.
The efficiency of the archiver varies for different files. Programs are the least susceptible to packaging. Text files and some graphic files are compressed the most compactly. Compressed files can be stored, sent from place to place, but you cannot work with them. Before you can use a compressed file, you need to decompress (uncompress) it using the same uncompressor program with which the information was compressed.
The
Astra Linux operating system uses the Ark archiving program. It is a shell program used to manage several types of archives. This allows the user not only to work with archives understood by Linux systems but also to exchange archived data with Windows users.
There is one rule that must be respected to avoid incorrect operation of the archiving program. Do not work with archives – be it creating an archive or unpacking it – on external media. Before you start, copy the necessary files to your “Home” directory.
Before you start experimenting with archiving files, do the following steps. Create a SAFE folder in your Home folder and copy several files from any folder into it. Let’s set the following task: archive the files stored inside the SAFE folder by writing the result to a file named SAFE in the same SAFE folder.
1. Display the contents of the SEIF folder.
2. Highlight the files to be archived.
3. Right-click the highlighted files.
4. 4. From the menu that appears, select Pack and then Pack to Archive.
5. A window with the archiving options opens.
Path. The path to the folder where the archive file will be saved. It can be changed by clicking on the selection button to the right of the field.
File name. Name of the archive file.
Type. Type of the archive file. Three types of archives are available:
– ZIP
– 7-ZIP
– TAR – used for Linux systems.
This is a simple concatenation of the contents of all files. The size of the archive file will be equal to the total size of the included files. Additionally, this file can be compressed using other archivers; they are listed in the archive type selection list.
The best option is ZIP. A ZIP archive is treated equally by both Astra Linux and MS Windows operating systems. Therefore, if you have to prepare data to be transferred for processing to users working with MS Windows, you should choose this archiver. These archives can also be password protected.
Then click the Compression arrow
.
The compression options appear. You can set the archive compression ratio by moving the slider on the scale. The higher the compression ratio, the smaller the resulting archive volume, but at the same time the time to compress the files and uncompress the archive increases.
In the Astra Linux environment, the contents of the archive can be viewed without unpacking. To do this, double-click on the name of the archive file.
Selective unpacking of the archive is performed in the Ark window. Let us remind you how to access it. In the File Manager window, right-click on the archive name and select the Open command. The Ark window opens with a list of archived files. There are several ways to selectively unpack.
Creating a multivolume archive
Imagine
the following situation. You need to send a large volume of data by email. And the mail service has limitations on the size of the file attached to the message. In this case you can attach a file as a multivolume archive, i.e. an archive consisting of several files; the size of each file meets the mail service limitations.
In the Archive creation window, click the Multivolume archive arrow. The Create multivolume archive options appear. Select the Create multivolume archive check box. In the Volume Size field, enter the maximum size of a single volume. Enter a value of 5 MB.
Start the archive by clicking the Yes button.
The archive volumes will gradually appear in the File Manager window during the archiving process. The duration of the archive creation process depends on the size of the original data and the size of the volume.
From the book “Astra Linux.
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