5. Linux Branched

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• / root directory: origin of the tree
• root user
• are not the same!

✅ Level 0

• / means root, origin of the tree
• kernel
• root directory
• all mean the same

✅ Level 1

• all have a name /smth
• we store the most important components of Linux
• ⚠️ they can never be deleted

• only super user can delete it

• 👀 /bin, /home, /boot, /user…

☑️ Types of Level 1 branches

• ✔️ /bin
• binary files, executable files
• we have the commands that the users can execute

❓ I want user Diario to not be able to run a command
- I delete the command from /bin
- and move it to another place, and put a . on it

• ✔️ /sbin
• executable files for the super user

• commands that only the super user can execute

• ✔️ /boot
• partition with booting options
• we keep the GRUB if we have the legacy BIOS
• from /boot, if we chose UEFI, we will have /boot/efi

• and have the GRUB inside /boot/efi

• 💡 Note:
• sub branches(level 2 branch) can have different format from the main branch

• for example, /boot and /boot/efi can have different format

• 💡 Note:
• If we keep updating the Linux many times,
• /boot will keep growing and occupy all 1GB
• 😱 Incident: so when you get a message no space in /boot
• 💊 ask super user to clean it
• with the command sudo apt autoremove
  • sudo: superuser do
  • apt: use the command in apt
  • autoremove: clean
• after this command, you can clean the /boot

• and go back to minimum 300MB

• ✔️ /dev

• branch in which all the disks and partitions of disks are represented/stored

  • the mountpoint for all the disks and partitions of disks
  • 👀 /dev/sda1
  • /dev/sda1 my partitions are hardware 🆚 /dev is software
  • so it is like a nickname
• ✔️ /etc
• for extras
• the most important first level branch!
• gives all the settings to the system
• the most important settings are there
• originally created for extra files,
• but after kernel 4, they started using it for the most important things

• 👀 users, passwords, setting files for my system…

• ✔️ /home
• personal folder
• dedicated to personal information
• in /home, there is a second level branch, per user
• so each user has each /home
• 👀 /home/shpl
• my personal folder will have a little nickname ~
• ~ 🟰 /home/shpl
• if you send files to ~, you are sending files to personal directories

❓ What do we have inside ~?

• they will be level 3 branches
• Downloads(level 3), /home/shpl/downloads
• Desktop
• Documents
• Pictures
• Templates
• videos

• Music

• What we have in ~ 🟰 /home/shpl is only visible for me

• 💡 Note:
• If you want to hide/secret a file/folder
• then add a . in front

• 👀 Downloads ➡️ .Downloads

• ✔️ /lib
• specific files for making other files work

• in lib we have all the resources to run the commands for /bin

• ✔️ /slib
• library for the commands of the super user, that are in sbin

❓ If a command does not work, what is the two possibility happening?

1. we have a problem in the /lib
a missing /lib of that command
or corrupt library

2. the command disappeared from /bin

• ✔️ /lib64
• libraries for 64 bits
• nowadays everything is 64 bits
• so sometimes, this folder does not exist

• and everything is inside /lib

• ✔️ /root
• same as /home of the super user, which is /home/su
• /root: personal folder for super user
• when we become the super user, (⚠️ not recommended)
• our downloads, our pictures are no longer in ~

• they will be inside /root

• ✔️ /usr
• folder shared by users
• folders for users in general

• when you want to share smth with the other user, put it in the /usr directory

• this branch is always surveyed by super user

• so if you want to do smth in /usr you need to get the permission of super user

• ✔️ /sis
• all the events of the kernel
• everything that happens in the kernel
• events of failure in the kernel

• 👀 IPC warning messages

• ✔️ /proc

• all the events of failure

• ✔️ /srv
• server
• everything connected to internet settings
• 👀 /srv/www: everything that happens when we navigate on the internet
• 👀 /srv/ftp: everything that happens when we upload, download files

❓ If smth fails while the navigaing the web, where is the errors saved?

- /proc

When things are not with an error while navigating in the web?
- it would be stored in /srv/www

⭐️ Cheatsheet ⭐️
/srv/www: when navigation on internet goes ok
/srv/ftp: when you upload file to internet
/proc: when navigation fails
/sis: when the kernel fails

❓ I have a kernel booting error. Where can I check the error?
➡️ /sis

• ✔️ /opt
• store all the optional things that do not come with the standard download with the linux
• 🟰 things that do not come in the standard repositories

• 🟰 things that do not come with default in linux

  • 👀 tree: command to show you the tree
  • but to run this command, you have to install this command manually
  • does not come with linux initialization settings
  • so it would be inside /opt
• ✔️ /tmp
• temporal files
• forbidden to delete it manually ❌

• if you delete it, some commands will fail

• ✔️ /var
• branch for saving important system information

• 👀 systems variables

• ✔️ /media
• related to extra devices that do not come by default in /dev
• 👀 my partitions are in /dev
• but if I install a CD reader, USB reader, camera(not standard)
• they will be stored in /media
• 👀 Guest Additions are considered a iso, so it will be stored in the /media

💡 / is the root and separator

• /: we have the kernel here
• but / is also a separator
• also used for separating the branches

• 👀 /home/carlos is a branch hanging from /

• branch 🟰 directory
• in Linux, we do not say folders, we say directories

✅ Level 2

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