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--- linux:commands [2017/08/03 08:14] – [System informations] torpedo
+++ linux:commands [2023/12/03 11:09] – [Create link] tormec
@@ Line 1: / Line 1: @@
+====== Basic commands ======
+===== System informations =====
+To know name and version of one's Linux distribution:
+<code bash>
+cat /etc/lsb-release
+</code>
+To get kernel (''Architecture'') and processor architecture (''CPU op-mode(s)''): <code bash>
+lscpu
+</code>
+To view free and used memory:
+<code bash>
+free
+</code>
+To view free and used disk space:
+<code bash>
+df
+</code>
+To view a detailed description of the system's hardware components:
+<code bash>
+sudo dmidecode
+</code>
+<WRAP info>
+**Info:** to find out the maximum ram capacity of the computer, refer at ''type 16'' of ''dmidecode'' output, for instance:
+<code>
+Handle 0x000F, DMI type 16, 15 bytes
+Physical Memory Array
+	Location: System Board Or Motherboard
+	Use: System Memory
+	Error Correction Type: None
+	Maximum Capacity: 4 GB
+	Error Information Handle: Not Provided
+	Number Of Devices: 2
+</code>
+where ''Number of Devices'' is the number of slots.
+</WRAP>
+===== Switch among directories =====
+To come back from ''dir/sub-dir'' to the parent directory ''dir'':
+<code bash>
+cd ..
+</code>
+To go to any directory:
+<code bash>
+cd /absolute/path/folder
+</code>
+===== Visualize content of directory =====
+To visualize the content of a directory:
+<code bash>
+ls
+</code>
+To visualize hidden files as well:
+<code bash>
+ls -a
+</code>
+To visualize a detail list of all files (add the option ''-a'' to include also the hidden files):
+<code bash>
+ls -l
+</code>
+with the following output:
+^ type of file ^ permissions ^ hard links ^ owner ^ group ^ size in bytes ^ date last edit ^ name ^
+| ''d'' folder\\ ''-'' file |  owner group other|
+===== Create directory =====
+To create a directory with sub-directory:
+<code bash>
+mkdir folder/sub-folder
+</code>
+===== Rename directory =====
+To rename a directory:
+<code bash>
+mv old-name/ new-name/
+</code>
+this will **delete** the origin folder.
+===== Copy directory =====
+To copy a directory:
+<code bash>
+cp -r /absolute/path/from /absolute/path/to
+</code>
+this will **retain** the origin directory.
+===== Delete empty directory =====
+To delete an empty directory:
+<code bash>
+rmdir folder
+</code>
+===== Delete non empty directory =====
+To delete a **non** empty directory:
+<code bash>
+rm -r folder
+</code>
+===== Create file =====
+To create a file:
+<code bash>
+touch file.txt
+</code>
+===== Rename file =====
+To rename a file:
+<code bash>
+mv old-file.txt new-file.txt
+</code>
+this will **delete** the origin file.
+===== Copy file =====
+To copy a file:
+<code bash>
+cp /aboslute/path/from.txt /absolute/path/to.txt
+</code>
+this will **retain** the origin file.
+===== Delete file =====
+To delete a file:
+<code bash>
+rm file.txt
+</code>
+===== Create link =====
+To create a symbolic link (option ''-s''), which points to a file or a directory:
+<code bash>
+ln -s /absolute/path/origin /absolute/path/destination
+</code>
+Note that a symbolic link is just a path so that if the file or the directory is deleted the link will still work but will point to something that doesn't exist.
+===== Change permissions =====
+The general syntax to change the permissions for a file is:
+<code>
+chmod <options> <people><operator><permission> <file|folder>
+</code>
+where:
+^  ''<people>''  ^  ''<operator>''  ^  ''<permission>''  ^
+| ''u'' users | ''+'' add \\ ''-'' remove \\ ''='' remove previously and set new | ''r'' read \\ ''w'' write \\ ''x'' execute |
+| ''g'' group | ::: | ::: |
+| ''o'' others | ::: | ::: |
+For instance:
+<WRAP group>
+<WRAP half column>
+<code bash>
+chmod ugo=rwx file.py
+</code>
+</WRAP>
+<WRAP half column>
+owner, group and others: read, write and execute
+</WRAP>
+</WRAP>
+<WRAP group>
+<WRAP half column>
+<code bash>
+chmod u=rwx file.py
+</code>
+</WRAP>
+<WRAP half column>
+owner: reads, writes and executes (previously permissions for group and others are removed)
+</WRAP>
+</WRAP>
+<WRAP group>
+<WRAP half column>
+<code bash>
+chmod u=xw,g=r,o=rw file.py
+</code>
+</WRAP>
+<WRAP half column>
+owner: writes and reads; group: reads; others: reads and writes (for all, previously permissions are replaced with the new ones)
+</WRAP>
+</WRAP>
+<WRAP group>
+<WRAP half column>
+<code bash>
+chmod u+r,g-r,o=x file.py
+</code>
+</WRAP>
+<WRAP half column>
+owner: added read permission; group: removed read permission; others: executes
+</WRAP>
+</WRAP>
+<WRAP group>
+<WRAP half column>
+<code bash>
+chmod -R o=rw folder file.py
+</code>
+</WRAP>
+<WRAP half column>
+others: reads and writes (permission applied recursively at directory and file)
+</WRAP>
+</WRAP>
+===== Find string =====
+To find a string:
+<code bash>
+grep -ilr 'string to find' *
+</code>
+where:
+^ options ^ ^
+| ''-i'' | case insensitivity |
+| ''-l'' | list results printing only name files |
+| ''-r'' | recursive search  |
+<WRAP tip>
+**Tip:** wrap the string in superscripts only if it contains blank spaces.
+</WRAP>
+To save the output in a text file:
+<code bash>
+grep -ril 'string to find' * > /absolute/path/output.txt
+</code>
+To find a string at the start of a line:
+<code bash>
+grep -ril '^string to find' /absolute/path
+</code>
+To find a string at the end of a line:
+<code bash>
+grep -ril 'string to find$' /absolute/path
+</code>
+===== Find file =====
+To find a file in a directory hierarchy:
+<code bash>
+find /directory file.txt
+</code>
+<WRAP tip>
+**Tip:** use ''sudo'' to search in directories where only the superuser has access.
+</WRAP>
+===== Processes in execution =====
+To know which processes are in execution:
+<code bash>
+top
+</code>
+To stop a process:
+<code bash>
+kill <PID>
+</code>
+where ''<PID>'' is the process's ID read from the output table of the command ''top''.
+===== List of logged in users =====
+To list the history of logged in users:
+<code bash>
+last
+</last>