GIT - fetch, rebase ...

 

Merging or Rebasing

Here I want to compare both methods. In this example will use few git functions.

Merging

Merge graph that looks below. To incorparate code from "feature branch" new knot on "main" branch is needed.

If I run a merge, git will stuff all of my changes from my feature branch into one large merge commit that contains ALL of my feature branch changes. It will then place this special merge commit onto master. When this happens, the tree will show your feature branch, as well as the master branch. Going further, if you imagine working on a team with other developers, your git tree can become complex: displaying everybody else’s branches and merges.

Rebasing

Now let’s take a look at how rebase would handle this same situation. Instead of doing a git merge, I’ll do a git rebase. What rebase will do is take all of the commits on your feature branch and move them on top of the master commits. Behind the scenes, git is actually blowing away the feature branch commits and duplicating them as new commits on top of the master branch (remember, under the hood, commit objects are immutable and immovable). What you get with this approach is a nice clean tree with all your commits laid out nicely in a row, like a timeline. Easy to trace.

Each method have positive and negative features. Each approach has to be established individually. 

In practice: the actual commands

On the development team I work with, we’ve successfully adopted the workflow I’m about to show you and it works well for us. If you’d like a visual representation of what each of these commands does, check out my video.

When I start development I always make sure the code on my local machine is synced to the latest commit from remote master

# With my local master branch checked out
git fetch origin

Next, I’ll check out a new branch so I can write and commit code to this branch – keeping my work separated from the master branch

git checkout -b FeatureBranch

As I’m developing my feature, I’ll make  commit.

git add .
git commit -m 'This is a new commit'

Since I synced with remote master before doing the rebase, I should be able to push my changes up to remote master without issues.

git push origin main

To save time, use aliases.

More info see Github repo  with history*.txt:

https://github.com/andsidor/Git_test

Basic linux commands

 

All Linux commands fall into one of the following four categories:

• Shell builtins - Commands built directly into the shell with the fastest execution.
• Shell functions - Shell scripts (grouped commands).
• Aliases - Custom command shortcuts.
• Executable programs - Compiled and installed programs or scripts.

Here I  show a list of typical Linux commands examples of how they work. I will present command in groups listed below:

• File and Directory Operations Commands
• File Permission Commands
• File Compression and Archiving Commands
• Process Management Commands
• System Information Commands
• Networking Commands
• IO Redirection Commands
• Environment Variable Commands
• User Management Commands

1. File and Directory Operations Commands

File and directory operations are fundamental in working with the Linux operating system. Here are some commonly used File and Directory Operations commands:

1a. pwd command

The pwd command (print working directory) is a shell builtin command that prints the current location. 

        pwd

1b. ls command

The ls command (list) prints a list of the current directory's content.

    ls

Additional options:

-Show as a list

    ls -l

-Show as list with hidden files

    ls -la

-Show files with filesize

    ls lah

1c. cd command

The cd command (change directory) is a shell builtin command for changing the current working directory:

cd <directory> (relative path)

cd <path> (full path)

1d. mkdir command

The mkdir command (make directory) creates a new directory in the provided location.

    mkdir <Name_new_directory>

1e. rmdir command

Use the rmdir command (remove directory) to delete an empty directory.

    rmdir <Name_direktory_to_delete>

1f. touch command

The primary purpose of the touch command is to modify an existing file's timestamp. To use the command, run:

    touch <filename>

The command creates an empty file if it does not exist. Due to this effect, touch is also a quick way to make a new file (or a batch of files).

1g. cat command

The cat command (concatenate) displays the contents of a file in the terminal (standard output or stdout). To use the command, provide a file name from the current directory:

    cat <file 1> <file 2>

! - To display with line number

     cat -n <file 1> <file 2>

1h. cp command

The main way to copy files and directories in Linux is through the cp command (copy).

    cp [Source_file] [Destination_file] 

! - To prevent overide file

cp -i [Source_file] [Destination_file] 

! - To copy directory recursively

cp -r [dir 1]  [dir 2] 

1i. mv command

Use the mv command (move) to move files or directories from one location to another.

    mv <filename> ~/Documents/<filename>

    mv <filename> <renamed_filename>

    

1j. rmdir/rm command

   rm <filename> (path local or full path)

The rm command (remove) deletes files or directories. To use the command for non-empty directories, add the -r tag.

1.k head command

Use the head command to truncate long outputs.

    head <file>

shows the first 10 lines of the <file>.

    head -n 5 <filee> 

displays the first 5 lines of the <file>.

1.l tail command

The Linux tail command does the opposite of head. Use the command to show the last ten lines of a file

    tail <file>

    tail -n 5 <file>

displays the last 5 lines of the <file>.

2. File Permission Commands

    File permissions on Linux and Unix systems control access to files and directories. There are three basic permissions: read, write, and execute. Each permission can be granted or denied to three different categories of users: the owner of the file, the members of the file’s group, and everyone else.

2.a chmod command

Use the chmod (change mode) command to change file and directory permissions. The command requires setting the permission code and the file or directory to which the permissions apply.

    chmod <permission> <file or directory>

Who

The “who” is a list of letters that specifies whom you’re going to be giving permissions to. These may be specified in any order.

u The user who owns the file (this means “you.”)

g The group the file belongs to.

o The other users

a all of the above (an abbreviation for ugo)

Permissions

Of course, the permissions are the same letters that you see in the directory listing:

r Permission to read the file.

w Permission to write (or delete) the file.

x Permission to execute the file, or, in the case of a directory, search it.

Example 1: Give read, write and execute permissions to the owner, read and execute permissions to the group and read and execute permissions to others

        chmod 755 file.txt

        chmod u=rwx,g=rx,o=rx file.txt

Example 2: Give read, write and execute permissions to the owner, read and execute permissions to the group and read and execute permissions to others

        chmod 755 directory

        chmod u=rwx,g=rx,o=rx directory

Example 3: Give read, write and execute permissions to the owner, read and execute permissions to the group and read and execute permissions to others

        chmod -R 755 directory

        chmod -R u=rwx,g=rx,o=rx directory

2.b chown  command

The chown command (change ownership) changes the ownership of a file or directory. To transfer ownership, use the following command as sudo:

    sudo chown <new owner name or UID> <file or directory>

(adduser - https://www.geeksforgeeks.org/adduser-command-in-linux-with-examples/)

! - https://phoenixnap.com/kb/linux-chown-command-with-examples

! - https://www.geeksforgeeks.org/addgroup-command-in-linux-with-examples/

Permission groups can be:

blank to signify the owner

g for group

o for others

a for all

Add or remove is

+ to add the permission

- to remove the permission

Permission type can be

r for read, copy and so forth

w for write, edit, delete and move

x to make it executable

Example 1: Change the ownership of a file. Txommand gives the ownership of the file to the root user and the root group.

        chown root:root file.txt

Example 2: Change the ownership of a directory. The command gives the ownership of the directory to the root user and the root group.

        chown root:root directory

Example 3: Change the ownership of a directory and all its subdirectories. The command gives the ownership of the directory and all its subdirectories to the root user and the root group.

        chown -R root:root directory

The Chown and Chmod commands are very similar. The only difference is that the Chown command is used to change the ownership of a file or directory and the Chmod command is used to change the permissions of a file or directory.

2.c 

chgrp

There is a third command called Chgrp that is used to change the group of a file or directory. The Chgrp command is used to change the group of a file or directory by using the following syntax:

chgrp [OPTIONS] GROUP FILE(s)

Example 1: Change the group of a file. Command gives the group of the file to the root group.

        chgrp root file.txt

Example 2: Change the group of a directory. Command gives the group of the directory to the root group.

        chgrp root directory

Example 3: Change the group of a directory and all its subdirectories. Command gives the group of the directory and all its subdirectories to the root group.

        chgrp -R root directory

chgrp marketing file.txt – to change the group specified to a certain document

chgrp oracle /usr/database – to change the group specified to a certain directory

chgrp -R marketing /sales/2008 – to change the group specified to a certain directory recursively

2.d chown command

chown: This command changes file owner and group.

chmod 600 some_file

Here is a table of numbers that covers all the common settings. The ones beginning with “7” are used with programs (since they enable execution) and the rest are for other kinds of files.

Value

777 (rwxrwxrwx) No restrictions on permissions. Anybody may do anything. Generally not a desirable setting.

755 (rwxr-xr-x) The file’s owner may read, write, and execute the file. All others may read and execute the file. This setting is common for programs that are used by all users.

700 (rwx——) The file’s owner may read, write, and execute the file. Nobody else has any rights. This setting is useful for programs that only the owner may use and must be kept private from others.

666 (rw-rw-rw-) All users may read and write the file.

644 (rw-r–r–) The owner may read and write a file, while all others may only read the file. A common setting for data files that everybody may read, but only the owner may change.

600 (rw——-) The owner may read and write a file. All others have no rights. A common setting for data files that the owner wants to keep private.

Here are some useful settings for directories:

Value Meaning

777 (rwxrwxrwx) No restrictions on permissions. Anybody may list files, create new files in the directory and delete files in the directory. Generally not a good setting.

755 (rwxr-xr-x) The directory owner has full access. All others may list the directory, but cannot create files nor delete them. This setting is common for directories that you wish to share with other users.

700 (rwx——) The directory owner has full access. Nobody else has any rights. This setting is useful for directories that only the owner may use and must be kept private from others.

chmod 755 file.txt

The above command is equivalent to the following command:

chmod u=rwx,g=rx,o=rx file.txt

2.4 umask command

The umask command in Linux is used to set default permissions for files or directories the user creates.

TBD

3. File Compression and Archiving Commands

Here are some file compression and archiving commands in Linux:

tar - https://www.geeksforgeeks.org/tar-command-linux-examples/

gzip - https://www.geeksforgeeks.org/gzip-command-linux/

zip - https://www.geeksforgeeks.org/zip-command-in-linux-with-examples/

4. Process Management Commands

In Linux, process management commands allow you to monitor and control running processes on the system. Here are some commonly used process management commands:

ps - https://www.geeksforgeeks.org/ps-command-in-linux-with-examples/

top - https://www.geeksforgeeks.org/top-command-in-linux-with-examples/

kill - https://www.geeksforgeeks.org/kill-command-in-linux-with-examples/

pkill - https://www.geeksforgeeks.org/kill-command-in-linux-with-examples/

grep - https://www.geeksforgeeks.org/grep-command-in-unixlinux/

5. System Information Commands

In Linux, there are several commands available to gather system information. Here are some commonly used system information commands:

uname - Print effective user name

whoami - Print effective user name

df - Report file system space usage

du - Estimate file space usage

free - Total usable memory

uptime - Utility for removing user

lscpu - Display CPU information

lspci - List PCI devices.

lsusb - List USB devices

exit - List USB devices

clear - List USB devices

passwd - Change user password

useradd - Create a new user or update default new user information

userdel - Utility for removing user

6. Networking CommandsDisplay network socket information.

In Linux, there are several networking commands available to manage and troubleshoot network connections. Here are some commonly used networking commands:

ifconfig - https://www.geeksforgeeks.org/ifconfig-command-in-linux-with-examples/

ping - https://www.geeksforgeeks.org/ping-command-in-linux-with-examples/

netstat - https://www.geeksforgeeks.org/netstat-command-linux/

ss - Display network socket information.

ssh - https://www.geeksforgeeks.org/ssh-command-in-linux-with-examples/

scp - https://www.geeksforgeeks.org/scp-command-in-linux-with-examples/

wget - https://www.geeksforgeeks.org/wget-command-in-linux-unix/

curl - https://www.geeksforgeeks.org/curl-command-in-linux-with-examples/

7. IO Redirection Commands 

In Linux, IO (Input/Output) redirection commands are used to redirect the standard input, output, and error streams of commands and processes. Here are some commonly used IO redirection commands:

Command	Description
cmd < file	Input of cmd is taken from file.
cmd > file	Standard output (stdout) of cmd is redirected to file.
cmd 2> file	Error output (stderr) of cmd is redirected to file.
cmd 2>&1	stderr is redirected to the same place as stdout.
cmd1 <(cmd2)	Output of cmd2 is used as the input file for cmd1.
cmd > /dev/null	Discards the stdout of cmd by sending it to the null device.
cmd &> file	Every output of cmd is redirected to file.
cmd 1>&2	stdout is redirected to the same place as stderr.
cmd >> file	Appends the stdout of cmd to file.

8. Environment Variable Commands

In Linux, environment variables are used to store configuration settings, system information, and other variables that can be accessed by processes and shell scripts. Here are some commonly used environment variable commands:

Command	Description
export VARIABLE_NAME=value	Sets the value of an environment variable.
echo $VARIABLE_NAME	Displays the value of a specific environment variable.
env	Lists all environment variables currently set in the system.
unset VARIABLE_NAME	Unsets or removes an environment variable.
export -p	Shows a list of all currently exported environment variables.
env VAR1=value COMMAND	Sets the value of an environment variable for a specific command.
printenv	Displays the values of all environment variables.

9. User Management Commands

In Linux, user management commands allow you to create, modify, and manage user accounts on the system. Here are some commonly used user management commands:

Command	Description
who	Show who is currently logged in.
sudo adduser username	Create a new user account on the system with the specified username.
finger	Display information about all the users currently logged into the system, including their usernames, login time, and terminal.
sudo deluser USER GROUPNAME	Remove the specified user from the specified group.
last	Show the recent login history of users.
finger username	Provide information about the specified user, including their username, real name, terminal, idle time, and login time.
sudo userdel -r username	Delete the specified user account from the system, including their home directory and associated files. The -r option ensures the removal of the user’s files.
sudo passwd -l username	Lock the password of the specified user account, preventing the user from logging in.
su – username	Switch to another user account with the user’s environment.
sudo usermod -a -G GROUPNAME USERNAME	Add an existing user to the specified group. The user is added to the group without removing them from their current groups.

10. Shortcuts Commands

There are many shortcuts commands in Linux that can help you be more productive. Here are a few of the most common ones:

10.1: Bash Shortcuts Commands:

Navigation	Description	Editing	Description	History	Description
Ctrl + A	Move to the beginning of the line.	Ctrl + U	Cut/delete from the cursor position to the beginning of the line.	Ctrl + R	Search command history (reverse search).
Ctrl + E	Move to the end of the line.	Ctrl + K	Cut/delete from the cursor position to the end of the line.	Ctrl + G	Escape from history search mode.
Ctrl + B	Move back one character.	Ctrl + W	Cut/delete the word before the cursor.	Ctrl + P	Go to the previous command in history.
Ctrl + F	Move forward one character.	Ctrl + Y	Paste the last cut text.	Ctrl + N	Go to the next command in history.
Alt + B	Move back one word	Ctrl + L	Clear the screen.	Ctrl + C	Terminate the current command.
Alt + F	Move forward one word.

10.2: Nano Shortcuts Commands:

File Operations	Description	Navigation	Description	Editing	Description	Search and Replace	Description
Ctrl + O	Save the file.	Ctrl + Y	Scroll up one page.	Ctrl + K	Cut/delete from the cursor position to the end of the line.	Ctrl + W	Search for a string in the text.
Ctrl + X	Exit Nano (prompt to save if modified).	Ctrl + V	Scroll down one page.	Ctrl + U	Uncut/restore the last cut text.	Alt + W	Search and replace a string in the text.
Ctrl + R	Read a file into the current buffer.	Alt + \	Go to a specific line number.	Ctrl + 6	Mark a block of text for copying or cutting.	Alt + R	Repeat the last search.
Ctrl + J	Justify the current paragraph.	Alt + ,	Go to the beginning of the current line.	Ctrl + K	Cut/delete the marked block of text.
		Alt + .	Go to the end of the current line.	Alt + 6	Copy the marked block of text.

10.3: VI Shortcuts Commands:

Command	Description
cw	Change the current word. Deletes from the cursor position to the end of the current word and switches to insert mode.
dd	Delete the current line.
x	Delete the character under the cursor.
R	Enter replace mode. Overwrites characters starting from the cursor position until you press the Escape key.
o	Insert a new line below the current line and switch to insert mode.
u	Undo the last change.
s	Substitute the character under the cursor and switch to insert mode.
dw	Delete from the cursor position to the beginning of the next word.
D	Delete from the cursor position to the end of the line.
4dw	Delete the next four words from the cursor position.
A	Switch to insert mode at the end of the current line.
S	Delete the current line and switch to insert mode.
r	Replace the character under the cursor with a new character entered from the keyboard.
i	Switch to insert mode before the cursor.
3dd	Delete the current line and the two lines below it.
ESC	Exit from insert or command-line mode and return to command mode.
U	Restore the current line to its original state before any changes were made.
~	Switch the case of the character under the cursor.
a	Switch to insert mode after the cursor.
C	Delete from the cursor position to the end of the line and switch to insert mode.

10.4: Vim Shortcuts Commands:

Normal Mode	Description	Command Mode	Description	Visual Mode	Description
i	Enter insert mode at the current cursor position.	:w	Save the file.	v	Enter visual mode to select text.
x	Delete the character under the cursor.	:q	Quit Vim.	y	Copy the selected text.
dd	Delete the current line.	:q!	Quit Vim without saving changes.	d	Delete the selected text.
yy	Copy the current line.	:wq or $:x$	Save and quit Vim.	p	Paste the copied or deleted text.
p	Paste the copied or deleted text below the current line.	:s/old/new/g	Replace all occurrences of “old” with “new” in the file.
u	Undo the last change.	:set nu or :set number	Display line numbers.
Ctrl + R	Redo the last undo.