commit 1a6f74c030a244b90ce2e278ad4b3ea661ea17e5
Author: Gasper Spagnolo <gasper.spagnolo@outlook.com>
Date:   Mon Jul 25 13:05:35 2022 +0200

    first commit

diff --git a/Clipboard.md b/Clipboard.md
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+---
+title: Clipboard
+created: '2021-12-26T19:27:19.496Z'
+modified: '2021-12-26T19:27:45.794Z'
+---
+
+# Clipboard
+
+- `cat file.txt | xclip -selection clipboard -i` store file into clipboard
+
+### On wayland
+
+- `cat file.txt | wl-copy` store file into clipboard
diff --git a/Compression.md b/Compression.md
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+---
+tags: [linux]
+title: Compression
+created: '2021-11-06T22:08:33.761Z'
+modified: '2021-12-31T10:35:51.469Z'
+---
+
+# Compression
+### Tar archives
+
+- `tar -cf file.tar dir/` -archive using tar, extract `tar -xvf file.tar`
+- `sudo tar -czf file.tar.gz dir/` gzip dir
+
+### Gzip
+- `gunzip archive.gz`
+
+### Zip archives
+
+- `unzip -x <file.zip> -d <destination_dir>` - unzip
+-`zip -r {filename.zip} {foldername}` -zip
+
+
+### 7zip archives
+- `7z x <file.7z>` - unzip
+
diff --git a/Curl.md b/Curl.md
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+---
+tags: [linux]
+title: Curl
+created: '2021-12-05T22:26:06.249Z'
+modified: '2021-12-05T23:01:15.615Z'
+---
+
+# Curl
+
+### Download any file
+- `curl -o <file.extension> <url>` -download with new filename
+- `curl -O <url>` - download with original filename
+
+useful flags:
+- `-L` - use redirection
+- `-H 'key:value'` - add header
+
+- `curl -IL ssrd.io` - get information about server
+- `url -vL ssrd.io` - display handshake with a server
diff --git a/Dig.md b/Dig.md
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+---
+tags: [linux]
+title: Dig
+created: '2021-12-05T22:45:44.151Z'
+modified: '2021-12-05T22:46:14.308Z'
+---
+
+# Dig
+
+### Get all DNS records of a domain name
+- `dig ssrd.io ALL`
diff --git a/Find.md b/Find.md
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+---
+tags: [linux]
+title: Find
+created: '2021-10-27T23:21:40.274Z'
+modified: '2021-12-09T21:12:58.481Z'
+---
+
+# Find
+### Examples of find command
+- `sudo find / -type d -iname "gasper"` - search direcotry
+- `sudo find /etc -type f -name "*.conf"` - display all configuration files, for more percison you should `|`  into `grep`.
+
+
+You can also add `szie` flag to narrow down results to expected filesize. Other useful flags: `user`, `group`.
diff --git a/GIT.md b/GIT.md
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+---
+title: GIT
+created: '2021-12-14T21:11:06.500Z'
+modified: '2021-12-14T21:13:05.655Z'
+---
+
+# GIT
+
+- If you want to revert changes made to your working copy, do this:
+`git checkout .`
+- if you want to revert changes made to the index (i.e., that you have added), do this. Warning this will reset all of your unpushed commits to master!
+`git reset`
+- if you want to remove untracked files (e.g., new files, generated files): `git clean -f` and dirs `git clean -fd`
+- if you want only one file to be revetred
+`git checkout HEAD -- TIS/tis.tex`
+- Add all files in the repo
+`git add -A`
diff --git a/Locate.md b/Locate.md
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+---
+tags: [linux]
+title: Locate
+created: '2021-10-25T21:52:02.050Z'
+modified: '2021-12-09T21:08:10.036Z'
+---
+
+# Locate
+### Examples of locate command
+use whatis/man locate for more info
+
+- `locate --all "passwd"`
+- `locate /etc --all "passwd"`
+- `locate "passwd" | grep "/etc/"`
+- `locate --all "*.conf" | grep resolv`
+- `locate --all "*conf" | grep proxychains` 
+- `locate --all -c "*.conf"` -  Count number of files whith provided name / pattern
+
+Use `-i` parameter to search uppercase/lowercase !
diff --git a/Networking.md b/Networking.md
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+---
+tags: [linux]
+title: Networking
+created: '2021-11-08T22:28:05.169Z'
+modified: '2021-12-09T21:20:59.016Z'
+---
+
+# Networking
+
+### IP command
+
+- `ip route show` -- display all routes `man ip | grep route` -- neat way to find more information about this command
+- `ip a` -- display all interfaces
+
+
+### Netstat command
+
+
+- `netstat -r` -- show routes
+- `netstat -t` -- display all current tcp connections, useful with grep command
+- `netstat -ltnp / -lu` list local TCP or UPD connections
+
+If u dont wont get cought use` tor + proxychains`
+
+### Proxychains
+- `systemctl start tor`
+- [setup](https://medium.com/cyberxerx/how-to-setup-proxychains-in-kali-linux-by-terminal-618e2039b663)
+
+### Nmap
+- [cheat-sheet](https://hackertarget.com/nmap-cheatsheet-a-quick-reference-guide/)
+
+### Sslscan
+Queries SSL/TLS services (such as HTTPS) and reports the protocol versions, cipher suites, key exchanges, signature algorithms, and certificates in use.  This helps the user understand which parameters are weak from a security standpoint.
+
+### Whois
+Find information about domain name `whois spanskiduh.xyz`
diff --git a/SSH.md b/SSH.md
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+---
+tags: [linux]
+title: SSH
+created: '2021-11-25T00:11:55.575Z'
+modified: '2021-12-09T21:54:30.814Z'
+---
+
+# SSH
+
+### basic
+- `/etc/ssh/ssh_config` - config location (client)
+- `/etc/ssh/sshd_config` - config location (server)
+
+It is *always* smart to disable root login!
+--> uncomment `PermitRootLogin no`
+
+### Enable encryption
+
+- `ssh-keygen -t rsa` - generate private and public key
+- `ssh-copy-id <server-ip>` - copy ssh identity to server
+
+--> uncomment `PasswordAuthentication no` (on server)
+**Warning** store private key on a secure location, if you lose it, you will lose connection to a server!
+
+### FAIL2BAN
+- use it to secure ssh
+- install a basic ubuntu vm and watch from 4:20 in video he he u get it, but it is actually there
+
+### SCP
+- `scp <filename> <user@server_ip:/destination_folder>` - copy file to server
diff --git a/Tracks.md b/Tracks.md
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+---
+tags: [linux]
+title: Tracks
+created: '2021-12-09T20:43:41.061Z'
+modified: '2021-12-09T21:41:06.195Z'
+---
+
+# Tracks
+
+- `/var/log` - Location of kernel and software logs
+- `shred -vzfu auth.log` -read manual, tool that overrites file many times causing data to be unrecoverable
+
+- `.bash_history` - do not forget this bro
diff --git a/VFS.md b/VFS.md
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+# VFS
+
+## Superblock
+Representation of mounted filesystem.
+properties:
+    - device, where the fs is located
+    - fs type
+    - block size
+    - flags
+    - root inode pointer (!)
+    - low level operations on the filesystem
+
+## Inode
+File of any type. Represents everything, except the filename!
+properties:
+    - includes pointers to blocks with data!!!
+    - owner, group, perms info
+    - inode number, file size.
+    - date & time of most recent access
+
+## Dentry
+It maps file names to to inodes
+properties:
+    - filename
+    - inode pointer that represents file
+    - pointer to parent dirent
+    - counter of usages
diff --git a/VIM.md b/VIM.md
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+---
+tags: [linux]
+title: VIM
+created: '2022-01-24T16:09:57.858Z'
+modified: '2022-01-24T16:10:20.634Z'
+---
+
+# VIM
+Comment Multiple Lines
+- `:15,25s/^/#` ~  comment from line 15 to 25.
+- `%s/foo/bar/g` ~ replace all apearances of `foo` with `bar` in whole file
+- `s/foo//g` ~ delete all apearances of `foo` in a line
+- `:[range]s/{pattern}/{string}/[flags] [count]` this is how it is structured out
+
+### Navigation
+- `hjkl` from now on use this keys
+- `x[visual]` delete character at current pos
+- `dw[visual]` delete a word
+
+-- vimtutor 2.5
+
+
+#### Nerdtree
+- `s` - open horizontally
+- `i` - open vertically
+
+#### Panes
+- `ctrl + w` - move through panes
+- `ctrl + w s` - split horizontally
+- `ctrl + w v` - split vertically 
+
+### Coc
+
+#### code navigation
+- `VISUAL over function name -> gd` ~ go to function definition
+- `VISUAL over data type -> gy / gi` ~ go to type definition
+- `VISUAL over function/ datatype -> K` ~ show documentation
+- `INSERT -> ctl + space` ~ toggle autosuggestions
+- `ctl + o` ~ return back
+- `VISUAL gf` ~ go to file
+- `ctl + o` ~ take me where i have bene before
+- `ctrl + i` ~ take me forward
+
+### Save
+- `:sav file.txt` ~ save new file
+- `:new file.txt` ~ create new file and open horizontally
+- `:vsp file.txt` ~ create new file and open vertically
diff --git a/adress_space.md b/adress_space.md
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+# Adress space
+
+## AS in C
+```
+[code       ]
+[init data  ]
+[uninit data]
+[heap       ]
+[    |      ]
+[    .      ]
+[   free    ]
+[    .      ]
+[    |      ]
+[stack      ]
+[args + env ]
+```
diff --git a/bash.md b/bash.md
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+#  Bash
+
+### Read file line by line using bash
+Gotta love those oneliners ;)
+```bash
+    while read line; do printf "$line\n"; printf "other commands\n"; done < /etc/passwd
+```
diff --git a/binary-patching.md b/binary-patching.md
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+---
+tags: [linux]
+title: Binary Patching
+created: '2021-12-05T22:45:44.151Z'
+modified: '2021-12-05T22:46:14.308Z'
+---
+
+# Binary patching
+firstly check in ghidra what hex value has function call. then open binary in vim, find that and replace all fucntion hex values with 90
+`:%!xxd` and `:%!xxd -r`    
+
diff --git a/binary_vs_text_files.md b/binary_vs_text_files.md
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+# Binary vs text files
+
+### Binary vs text files comparisson
+- read this awesome article https://www.geeksforgeeks.org/difference-between-cpp-text-file-and-binary-file/
+- Basically normal text files take more space than binary files, becouse you need to convert integer representation of number into chars. In binary file
+format, the raw binary data is dumped into file. --> that results in much smaller file size
diff --git a/disk-usage.md b/disk-usage.md
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+---
+tags: [linux]
+title: Disk usage
+created: '2021-11-06T21:52:39.114Z'
+modified: '2021-12-09T21:13:42.734Z'
+---
+
+# Disk usage
+### Very useful tool
+
+- `du -sh *` - list all folders an sizes in current folder
+- `df -h` display filesystem usage
+
diff --git a/docker.md b/docker.md
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+++ b/docker.md
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+# Docker
+
+## Nuke docker
+```bash
+
+#!/bin/bash
+
+printf "Stopping all containers\n"
+docker ps | awk ' {print $1} ' | xargs docker kill
+
+printf "Deleting all containers\n"
+docker container ls --filter "status=exited" | awk '{ print $1 }' | xargs docker container rm
+
+printf "Deleting all images\n"
+docker image ls | awk '{print $3}' | xargs docker image rm --force
+```
diff --git a/document-conversion.md b/document-conversion.md
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+++ b/document-conversion.md
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+
+### Pandoc
+- `pandoc -o doc.pdf doc.md` - convert md to pdf
diff --git a/exec.md b/exec.md
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+++ b/exec.md
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+# EXEC
+It is a family of functions that do the same thing but actually no.
+When we call `exec()`, we never reutrn back to the callling program. The program
+called by the `exec()` function replaces itself with the calling progam. The only way
+that we could return to original process if `exec()` fails to execute.
+Thats why we usually use `fork() & exec()`, so that we can safely return to main process
+without losing anything :).
+
+what stays:
+- `PID`, `PPID`
+- opened file descriptors
+- current directory, root directory
+
+what does not:
+- code
+- stack
+- heap
+- data 
+
+(new stack and new heap)
+
+sufixes:
+- `l` ~ arguments are passed as function arguments
+- `v` ~ arguments are passed by char array
+- `p` ~ search in `$PATH` for provided executable
+- `P` ~ specifying that we will provide a path to an executable
+- `e` ~ enviromental variables are provided in a char array
+
diff --git a/ffmpeg.md b/ffmpeg.md
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+# FFMPEG
+
+## Converting .mp3 into .wav
+`ffmpeg -i file.mp3 newfile.wav`
+
+## Cutting audio/video
+` ffmpeg -i f24122a7f35de434d996.ogg -ss 00:00:00 -to 00:00:30 -c copy mini.ogg`
diff --git a/forensics.md b/forensics.md
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+# FORENSICS
+
+### Sleuthkit
+- [sleuthkit commands](http://wiki.sleuthkit.org/index.php?title=The_Sleuth_Kit_commands)
+- always check the offset with `mmls` command
+- `sudo mount -o loop,offset=9437184 disk_image.img /mnt/iso` ~ mount iso img with offset
+- or option2 (better imho):
+    - `udisksctl loop-setup --file disk.img` ~ this will create loop devices in `/dev/loopX`
+    - then mount partitions as usual drive
+    - to unomount, use flags `-f -l`
+
+
+### Pdfgrep
+- is another fancy tool to grep text in pdf files
diff --git a/fork.md b/fork.md
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+# Fork
+
+### What happenes when you call `fork()` in your program?
+Parent creates a child and spawns it, it is basically a copy of a parent process
+
+excluding:
+- `PID`, `PPID`
+- file locks, mutex locks, any other locks...
+
+including:
+- same code
+- !copy! of same heap and stack
+- opened files
+
+### Example
+```c
+int pid = fork()
+if (pid > 0){
+    // parent process
+} else if (pid == 0) {
+    // child process
+} else {  // pid < 0
+    // we encountered err!
+}
+```
+
+### What happenes when cild process is exited?
+Exit status is saved in process descriptor, until parent process waits for it.
+Until exit status is not taken then we say that the process is **zombie**:
+- proces is exited, and it does not take any system resources.
+- only its process descriptor is not yet taken
+- and we do not want many zombies in our system
+
+
+### How parent knows, that the child process has been terminated?
+Well we can use `singal()` to notify parent when the child process exits. Namely signal `WAITCHLD`.
+
+Waiting for specific child:
+```c
+waitpid(pid, &status, options)
+```
+Waiting for any child:
+```c
+wait(&status);
+// or 
+waitpid(-1, &status, 0):
+```
+
+### Exit statuses
+- 8bit value
+- 0 means success
+- 1-127 error
+- 128-255 termination becouse of singal (`sig_num = status - 127`)
+
+## `vfork()` function
+V fork is a modified fork, which does not copy any data. It is meant to be used with comibnation with function `exec()`.
diff --git a/gcc.md b/gcc.md
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+++ b/gcc.md
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+# GCC
+
+### compilation flags
+- `-g` ~ enable debugging mode (for gdb to show running c code also)]
+- `-Wall` ~ enable all warnings
+- `-o binary` ~ output to binary file
+- `-S` ~ also compile asm file
diff --git a/gdb.md b/gdb.md
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+++ b/gdb.md
@@ -0,0 +1,49 @@
+---
+tags: [linux]
+title: Gdb
+created: '2021-12-05T22:45:44.151Z'
+modified: '2021-12-05T22:46:14.308Z'
+---
+
+# Gdb
+
+### Basics
+- `r` ~ run program
+- `ni` ~ step to next instruction
+- `c` ~ coninue execution of program to breakpoint or end of program if no breakpoint is set
+- `b *main` ~ add a breakpoint at main
+- `b *0xdeadbeef` ~ add a breakpoint at a specific addres
+- `info break` ~ list all breakpoints
+- `delete breakpoint <number>` ~ delete breakpoint with provided `number` breakpoint identifier
+- `x/30gx $rsp` ~ display first 30 values, after a stack pointer
+- `x/s 0x0000000040080e` ~ display a **string** at provided addres
+- `disass main` ~ disassembly provided function
+- `x/4i 0x0000000000401393` ~ get 4 instructions on provided address
+
+#### Show all secitons of a file
+- `info file`
+
+#### Display current state of registers
+- `info registers`
+
+#### List all maped memory regions
+- `info proc mappings`
+
+### Check protections used on a file
+issue command `checksec`
+- `Canary` ~
+- `NX` ~
+- `PIE` ~
+- `Fortify` ~ nobody knows
+- `RelRO` ~ 
+
+### ROP gadgedts
+- `~/.local/bin/ROPgadget --binary a.out`
+- registers:
+    - `rdi` ~ first argument
+    - `rsi` ~ second argument
+
+### HEAP
+- `vis` ~ show heap visually
+- `heap` ~ display chunks
+- `bins` ~ diplay TCACHE, FASTBIN, UNSORTED BIN pointers
diff --git a/mosquitto.md b/mosquitto.md
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+# Mosquitto
+
+Very nice IOT messaging protocol.
+
+### How to publish and subscribe to mqtt messages:
+
+#### Publish
+`mosquitto_pub -h <host-ip> -p <host-port> -u <username> -P <password> -t <topic> -m '<message>'`
+#### Subscribe
+`mosquitto_sub -h <host-ip> -p <host-port> -u <username> -P <password> -t <topic>`
diff --git a/mount.md b/mount.md
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+++ b/mount.md
@@ -0,0 +1,4 @@
+# Mount
+
+### Mount windows partition
+`sudo mount -t ntfs3 /dev/sdb1 /mnt/usb`
diff --git a/named_pipes.md b/named_pipes.md
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+++ b/named_pipes.md
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+# Named pipes
+
+They are very useful for transmiting data of one linux process to another.
+
+### Creation of named pipe
+- `mkfifo my_pipe`
+
+### Sending and recieving data
+- `echo "Hello my friend!" > my_pipe` ~ sending data to pipe
+- `tail -f my_pipe` ~ reading data from pipe
diff --git a/permissions.md b/permissions.md
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+++ b/permissions.md
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+# PERMS
+
+### Structure
+```bash
+            u   g   o
+            7   5   4
+          /     |     \
+type:   r w x  r w x  r w x
+repr:   4 2 1  4 2 1  4 2 1
+enabl:  1 1 1  1 0 1  1 0 0
+res:    4 2 1  4 0 1  4 0 0
+          7      5      4
+```
diff --git a/pipewire.md b/pipewire.md
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+++ b/pipewire.md
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+# PIPEWIRE
+
+### Fix for sony
+`https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/688`
diff --git a/pwn.md b/pwn.md
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+++ b/pwn.md
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+# PWN
+
+## Format1
+- `%12$p` ~ display value of offset 12 
diff --git a/qemu.md b/qemu.md
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+++ b/qemu.md
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+# Qemu
+
+### Emulating raspberry pi 4
+
+- firstly generate two images
+`qemu-img create -f qcow2 arm.img 16G` ~ Image for os
+`qemu-img create -f qcow2 varstore.img 64M` ~ EFI varaible store
+- then download EFI file (A UEFI image for QEMU’s virt machine type, I use an EDK II derived snapshot image from Linaro)
+`http://snapshots.linaro.org/components/kernel/leg-virt-tianocore-edk2-upstream/latest/QEMU-AARCH64/RELEASE_GCC5/QEMU_EFI.img.gz`
+
+- install
+`qemu-system-aarch64 \                                                    
+    -cpu cortex-a72 -smp 4 -M virt -m 4096 -nographic \
+    -drive if=pflash,format=raw,file=QEMU_EFI.img \
+    -drive if=pflash,file=varstore.img \
+    -drive if=virtio,file=arm.img\
+    -drive if=virtio, format=raw, file=file.iso`
+- run
+`qemu-system-aarch64 \                                                    
+    -cpu cortex-a72 -smp 4 -M virt -m 4096 -nographic \
+    -drive if=pflash,format=raw,file=QEMU_EFI.img \
+    -drive if=pflash,file=varstore.img \
+    -drive if=virtio,file=arm.img\`
diff --git a/regex.md b/regex.md
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--- /dev/null
+++ b/regex.md
@@ -0,0 +1,4 @@
+# REGEX
+
+### Reversing regex
+`exrex "flag\{wa{0}e[^abcdrfghijknmopqrstuvwxyz]c(((o)))(?=[a-z])[^a-ln-z]e_to_dc{0}ctf{1}\}" -o out.txt` - you can list all possible words accepted by regex with this tool
diff --git a/rust.md b/rust.md
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--- /dev/null
+++ b/rust.md
@@ -0,0 +1,8 @@
+# RUST
+
+### Basic cli tools 
+
+- `cargo init` ~ create new rust project
+- `cargo run` ~ build & run
+- `cargo build` ~ just build
+- `cargo build --release` ~ minimal release version (optimized)
diff --git a/services-and-process-management.md b/services-and-process-management.md
new file mode 100755
index 0000000..445fede
--- /dev/null
+++ b/services-and-process-management.md
@@ -0,0 +1,17 @@
+---
+tags: [linux]
+title: Services and process management
+created: '2021-11-24T23:37:56.443Z'
+modified: '2021-12-09T21:40:19.872Z'
+---
+
+# Services and process management
+
+### PS command
+- `ps aux` - display  **all** running services (snapshot)  ex. `ps aux | grep "ssh"`
+- `sudo kill <pid>` - kill process with provided pid, provided by `ps` command
+- `pkill <process-name>` - kill process by name :sunglasses:
+
+## on systemd u can also
+- `systemctl | grep <service_name>` - display all running services or grep one
+- `sudo systemctl is-enabled ssh` - check if service is enabled
diff --git a/sorting_algorithms.md b/sorting_algorithms.md
new file mode 100644
index 0000000..e675568
--- /dev/null
+++ b/sorting_algorithms.md
@@ -0,0 +1,58 @@
+# Sorting algorithms
+
+### FCFS
+Basically a fifo
+
+### RR - round robin
+Round robin
+
+
+### SFJ
+Shortest first
+
+### PSFJ
+Preemptive
+Sepravi ti gledas tuki
+recimo da mas 
+A =  100
+B = 20
+C = 10
+
+pa uzames najprej A, potem A splitas po C ju, ker ima C najmanjso casovno obdelavo. Aka vedno uzames 10
+
+zgleda tko : A[0:10], pol B[0:10], pol C[0:10],pole A[10:20], B[10:20], A[20:90]
+
+
+### Stride
+
+Najprej uzames najbol levega /shrug
+a = step 10
+b = step 30
+c = step 20
+
+Nato vedno v vsaki iteraciji pristejemo originalno ceno
+
+        A           B           C
+        0           0           0
+        10          0           0
+        10          0           20
+        10          30          20
+        20          30          20
+
+Pol pa mamo se un kurac od krititcnega stanja
+# Kriticno stanje
+
+```c
+// random primer
+x = 1 -> A_1
+y = 2 -> B_1
+
+x = x + y -> A_2
+y = x - y -> B_2
+```
+Pol gremo samo probat use mozne kombinacije
+
+sepravi A_1 B_1 A_2 B_2 --> in zracunas nc kej takega, lp in lpp
+
+atomarne operacije aka prireditvne in ne prisevanje / odstevanje se morejo vedno najprej izvest, v nasprotnem primeru 
+sploh nemores npr prsiteti x-a in y-a ---> segmetnation fault
diff --git a/symlinks.md b/symlinks.md
new file mode 100644
index 0000000..b7860ed
--- /dev/null
+++ b/symlinks.md
@@ -0,0 +1,36 @@
+# Difference between hardlinks and symlinks
+
+### Hardlinks
+- implementation of `ln`
+- kinda like shortcut, but a shortcut to a physical memory location!!!!
+
+```c
+/*
+ * creates new file, that points to same memory location as provided file
+ *  - if one of the files is edited, then both files change
+ *  - if one of the files gets deleted, then just inode of that file, that points to that location is deleted
+ *      other file stays undeleted, with same content
+ */
+int hardlink(char *dest, char *name) {
+    if(link(dest, name) < 0)
+       return errno;
+    return 0;
+}
+```
+
+### Softlinks
+- implementation of `ln -s`
+- it works like a shortcut to original file
+
+```c
+/*
+ * creates a new file, that points to provided file
+ *  - if one of the files is edited, then both files change
+ *  - if original file gets deleted, then also disk contents gets deleted, and link is broken
+ */
+int softlink(char *dest, char *name) {
+    if(symlink(dest, name) < 0)
+        return errno;
+    return 0;
+}
+```
diff --git a/system-information.md b/system-information.md
new file mode 100755
index 0000000..a769cbe
--- /dev/null
+++ b/system-information.md
@@ -0,0 +1,27 @@
+---
+favorited: true
+tags: [linux]
+title: System information
+created: '2021-10-27T22:55:40.432Z'
+modified: '2021-12-26T15:51:15.496Z'
+---
+
+# System information
+### Basic user enumeration
+
+- `whoami` `hostname` - get username and hostname
+- `id` - get information which group ids current user belongs to
+- `groups $USER` - check groups
+- `last` - check users that logged in recently
+
+
+### Cpu, memory
+- `lscpu` - show cpu information
+- `free -h` - display memory usage
+- `uname -p` or `uname -m` - show system architecture
+- `uname -r` - see a running kernel
+- `lsb_release -a` or `cat /etc/*release` - see running distribution
+
+### Another useful tool `sysstat` package
+- `iostat` - show current io (disk usage, cpu usage)
+- `mpstat` - show current cpu usage (detailed)
diff --git a/tmux.md b/tmux.md
new file mode 100755
index 0000000..2c0b1bf
--- /dev/null
+++ b/tmux.md
@@ -0,0 +1,26 @@
+---
+tags: [linux]
+title: Tmux
+created: '2021-12-05T22:45:44.151Z'
+modified: '2021-12-05T22:46:14.308Z'
+---
+
+# Tmux
+
+### Window operations
+- `ctrl+b c` - spawn new window
+- `ctrl+b n` - move to next window
+- `ctrl+b p` - move to previous window
+- `ctrl+b 0..9` - switch to window by number
+- `ctrl+b x` - kill current window
+
+### Panes
+- `ctrl+b %` - spawn new pane horizontally
+- `ctrl+b "` - spawn new pane vertically"
+- `ctrl+b arrow_key` - switch through panes
+- `ctrl+b ctrl + arrow_key` - resize pane
+- `ctrl+b o` - switch to next pane 
+- `ctrl+b loong o` - switch panes :sunglasses:
+- `ctrl+b space` - toggle pane layouts
+- `ctrl+b !` - convert pane into a window
+- `ctrl+b x` - kill current pane
diff --git a/uart.md b/uart.md
new file mode 100755
index 0000000..f31be2f
--- /dev/null
+++ b/uart.md
@@ -0,0 +1,16 @@
+---
+tags: [linux]
+title: Connect to uart
+created: '2021-12-02T13:30:36.053Z'
+modified: '2022-02-10T21:22:22.348Z'
+---
+
+# Connect to uart
+- `sudo dmesg | grep tty` - find uart device 
+- `sudo minicom -D /dev/ttyACM0 -b 115200` - connect to uart device
+
+ECHO TO UART DEVICE `ctrl + a e`
+
+(https://blog.mbedded.ninja/programming/operating-systems/linux/linux-serial-ports-using-c-cpp/)[programiranje uarta]
+
+LEAVE MINICOM (this is the hard one;;)   ctrl + a and then x
diff --git a/ufw.md b/ufw.md
new file mode 100755
index 0000000..7052d3e
--- /dev/null
+++ b/ufw.md
@@ -0,0 +1,19 @@
+---
+tags: [linux]
+title: ufw
+created: '2021-12-05T23:08:44.052Z'
+modified: '2021-12-09T20:29:32.892Z'
+---
+
+# ufw
+
+### Connections
+- `sudo ufw status numbered verbose` - check ufw status
+- `sudo ufw default deny incoming` - deny incoming connections
+- `sudo ufw default allow outgoing` - enable outgoing connections
+- `sudo ufw allow ssh` - allow certian connection (you can also specify a port number instead of protocol!)
+- `sudo ufw deny ssh` - deny certian connection
+- `sudo ufw allow/deny proto tcp from any to any port 80,443` - deny / allow all 80 and 443 connections
+- `sudo ufw allow from 192.168.1.103 to any port 22`- allow incomming ssh connections with specified ip. 
+- `sudo ufw allow from 192.168.1.1/24 to any port 22` - same thing, but now with specified subnet
+- `sudo ufw delete <rule-id>` - delete rule from ufw, get id with status command
diff --git a/wasm.md b/wasm.md
new file mode 100644
index 0000000..11eb43a
--- /dev/null
+++ b/wasm.md
@@ -0,0 +1,17 @@
+# Wasm
+h39df71edfbdc6cfb
+hffef93c8d94444c4
+## Usage of wabt
+
+- wat2wasm: translate from WebAssembly text format to the WebAssembly binary format
+- wasm2wat: the inverse of wat2wasm, translate from the binary format back to the text format (also known as a .wat)
+- wasm-objdump: print information about a wasm binary. Similiar to objdump.
+- wasm-interp: decode and run a WebAssembly binary file using a stack-based interpreter
+- wasm-decompile: decompile a wasm binary into readable C-like syntax.
+- wat-desugar: parse .wat text form as supported by the spec interpreter (s-expressions, flat syntax, or mixed) and print "canonical" flat format
+- wasm2c: convert a WebAssembly binary file to a C source and header
+- wasm-strip: remove sections of a WebAssembly binary file
+- wasm-validate: validate a file in the WebAssembly binary format
+- wast2json: convert a file in the wasm spec test format to a JSON file and associated wasm binary files
+- wasm-opcodecnt: count opcode usage for instructions
+- spectest-interp: read a Spectest JSON file, and run its tests in the interpreter