file and folder and rights

a user is only allowed to delete a file if he has WRITE access to the directory the file resides in.

id; # show userid and group id of currently logged in user
uid=1000(user) gid=100(users) Gruppen=100(users)

file artikel.txt; # tries to identify via magic numbers the type of file
artikel.txt: UTF-8 Unicode text

file sächsische_schweiz1.jpg
sächsische_schweiz1.jpg: JPEG image data, JFIF standard 1.01

# filetypes
ls -l
# file                symbol: -
# directory           symbol: d
# link                symbol: l (small L)
# device block        symbol: b
brw-rw----+ 1 root cdrom    11,   0 Apr 27 09:48 sr0
# device character    symbol: c
crw--w----  1 root tty       4,   0 Apr 27 09:48 tty0
# device named pipe   symbol: p
prw-r-----  1 root adm            0 Apr 27 09:49 xconsole|
# unix socket device  symbol: s
ll /tmp/.X11-unix/X0
srwxrwxrwx 1 root root 0 Apr 27 09:49 /tmp/.X11-unix/X0
ss -x -a ; # display all currently used unix sockets

ls -lF
       -F, --classify
              append indicator (one of */=>@|) to entries

type bash; # identify command (is it a binary? is it a script? is it an alias? and where is it?)
bash is /bin/bash

user@suse:~> ls -l; # list directory - show content of a direct
insgesamt 244
-rw-r--r-- 1 user users  2792 27. Apr 11:54 apache2.log
-rw-r--r-- 1 user users   172 27. Apr 11:13 artikel.txt
drwxr-xr-x 2 user users     6 24. Apr 13:45 Bilder
drwxr-xr-x 2 user users     6 24. Apr 13:01 bin
drwxr-xr-x 2 user users     6 24. Apr 13:45 Dokumente
drwxr-xr-x 2 user users     6 24. Apr 13:45 Downloads

# show userIDs groupIDs of files and folders
user@suse:~> ls -n
insgesamt 244
-rw-r--r-- 1 1000 100  2792 27. Apr 11:54 apache2.log
-rw-r--r-- 1 1000 100   172 27. Apr 11:13 artikel.txt
drwxr-xr-x 2 1000 100     6 24. Apr 13:45 Bilder
drwxr-xr-x 2 1000 100     6 24. Apr 13:01 bin
drwxr-xr-x 2 1000 100     6 24. Apr 13:45 Dokumente
drwxr-xr-x 2 1000 100     6 24. Apr 13:45 Downloads

user@suse:~> ls -iln; # show inode numbers, userIDs groupIDs of files and folders
insgesamt 244
      156 -rw-r--r-- 1 1000 100  2792 27. Apr 11:54 apache2.log
      150 -rw-r--r-- 1 1000 100   172 27. Apr 11:13 artikel.txt
      113 drwxr-xr-x 2 1000 100     6 24. Apr 13:45 Bilder
      100 drwxr-xr-x 2 1000 100     6 24. Apr 13:01 bin
134304866 drwxr-xr-x 2 1000 100     6 24. Apr 13:45 Dokumente
201326689 drwxr-xr-x 2 1000 100     6 24. Apr 13:45 Downloads

# changing access file and folder rights
# format: d rwx r-x --- =
# d = directory
# rwx = user(owner) has rwx (read,write,execute with directories means the user is allowed to change into that directory)
# r-x = members of the group have read rights and are also allowed to traverse the directory
# --- = others(all other users) have no rights

# two forms of changing file access rights
# r(ead)      = 4
# w(rite)     = 2
# (e)x(ecute) = 1
# rwx=4+2+1=7

chmod ugo=rwx artikel.txt; # version A
chmod 777     artikel.txt; # version B
ll
-rwxrwxrwx 1 user users 150 26. Apr 14:28 artikel.txt

chmod ugo=rw artikel.txt;   # version A
chmod 666    artikel.txt;   # version B
ll
-rw-rw-rw- 1 user users 150 26. Apr 14:28 artikel.txt

chmod 555    artikel.txt;   # version A
chmod ugo=rx artikel.txt;   # version B
ll
-r-xr-xr-x 1 user users   172 27. Apr 11:13 artikel.txt

chmod ugo=r  artikel.txt;   # version A
chmod 444    artikel.txt;   # version B
ll
-r--r--r-- 1 user users 150 26. Apr 14:28 artikel.txt

chmod ugo=r  artikel.txt;   # version A
chmod 222    artikel.txt;   # version B
ll
--w--w--w- 1 user users 150 26. Apr 14:28 artikel.txt

chmod ugo=  artikel.txt;   # version A
chmod 000   artikel.txt;   # version B
ll
---------- 1 user users 150 26. Apr 14:28 artikel.txt

su;        # become root
sudo bash; # become root
chown user:group artikel; # change the owner and group of file/folder
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