How to delete files securely, so i will be sure that there is no tracks left or at least less than simple deleting file? How process should look step by step for a)Linux b)Android?
I heard something about shredding or filling empty space but i wouldd like to see how to do that on these devices
For computers, see this PG article: Erasing Data Securely From Your SSD or HDD - Privacy Guides
As for Android or iOS, it’s fairly simple: They’ve been encrypted for quite a while, so just do a full phone reset, that will erase all your encryption keys permanently.
In addition to the Privacy Guides article, you can also read through similar threads for more information if you want:
Edit: Whoops, didn’t mean to reply specifically to Stiffly lol.
To summarize what these articles mention, there isn’t a reliable way to delete individual files. You would need to wipe entire partitions or the whole disk depending on your needs.
You can also look at BleachBit; I believe it was used by Hillary Clinton’s staff members to delete the emails stored in her personal email server.
If you are looking to delete individual files, Tails does have a “shred file feature”. However, this works mostly because Tails is already amnesiac. You shouldn’t rely on that feature if your threat model is high enough; you ought to wipe the entire USB stick instead.
Will using bleach bit add something more than just using command shred -u -v -n 7 /path/to/file ?
Not really but a GUI application would help a lot of people out.