How to Expose Docker API on CentOS

Docker provides an API for interacting with the Docker daemon (called the Docker Engine API), as well as SDKs for Go and Python. The SDKs allow you to build and scale Docker apps and solutions quickly and easily. If Go or Python don’t work for you, you can use the Docker Engine API directly.

The Docker Engine API is a RESTful API accessed by an HTTP client such as wget or curl, or the HTTP library which is part of most modern programming languages.

  • The version of the Docker Engine API you should use depends upon the version of your Docker daemon and Docker client.
  • The Docker API is backward-compatible, so you do not need to update code that uses the API unless you need to take advantage of new features.


How to Expose Docker API on Centos 7

– Check your docker daemon service loaded the file.

# sudo systemctl status docker

[[email protected]]# sudo systemctl status docker
● docker.service – Docker Application Container Engine
Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor preset: disabled)
Active: active (running) since Tue 2018-01-30 12:55:41 PST; 1 day 3h ago

– Open that file using your favorite editor

# sudo vi /usr/lib/systemd/system/docker.service

– Add -H tcp:// this code where starts with ExecStart.  You can also expose different port and IPs.

ExecStart=/usr/bin/docker daemon -H fd:// -H tcp://

– Save the modified file.

– Make sure the Docker service notices the modified configuration

# sudo systemctl daemon-reload

– Restart the Docker service

# sudo service docker restart

Test that the Docker API is accessible from outside.

# sudo curl <server-ip>:2375/images/json

It could be the security problem if we enabled the docker API via the public network and default port. Review the security concerns.


How to manage ESXi Firewall Configuration

ESXi hosts have an inbuilt firewall setting between the management interface and the rest of the network. The firewall is configured to drop all incoming and outgoing traffic but for a specific set of services in ESXi Host.In order to secure ESXi host by allowing only certain IP addresses or IP ranges after a fresh installation of ESXi, you can use the ESXi vSphere client, vCenter or vSphere ESXi CLI to configure the firewall settings.

Manage ESXi firewall Using vSphere client

It is an easy way to configure the firewall settings using a vSphere client or ESXi vCenter GUI.

  • Login your vSpere client
  • Click ESXi host
  • Go to Configuration
  • Click Security Profile under Software   – You can see the services list and firewall
  • Click Properties on Firewall Section
  • Select your service and click firewall
  • Update your IP address or IP range to allow traffic for your particular service.

ESXi Cli Commands


Manage ESXi firewall Using ESXi CLI

Login your ESXi host.

Use the following command to manage your Firewall settings.


esxcli network firewall get          – Returns the enabled or disabled status of the firewall and lists default actions.
esxcli network firewall set –default-action       – Update default actions.
esxcli network firewall set –enabled       – Enable or disable the ESXi firewall.
esxcli network firewall load         – Load the firewall module and rule set configuration files.
esxcli network firewall refresh       – Refresh the firewall configuration by reading the rule set files if the firewall module is loaded.
esxcli network firewall unload        – Destroy filters and unload the firewall module.
esxcli network firewall ruleset list       – List rule sets information.
esxcli network firewall ruleset set –allowed-all         – Set the allowed all flag.
esxcli network firewall ruleset set –enabled       – Enable or disable the specified rule set.
esxcli network firewall ruleset allowedip list       – List the allowed IP addresses of the specified rule set.
esxcli network firewall ruleset allowedip add       – Allow access to the rule set from the specified IP address or range of IP addresses.
esxcli network firewall ruleset allowedip remove       – Remove access to the rule set from the specified IP address or range of IP addresses.

ESXi CLI Command Examples

Display the firewall status

[[email protected]:~] esxcli network firewall get   Default Action: DROP   Enabled: true   Loaded: true

Specify specific IP Address or IP ranges to access a particular service. The following example disable the allow all option and specifies a particular range for the sshServer service.

[[email protected]:~] esxcli network firewall ruleset set --allowed-all false --ruleset-id=sshServer

[[email protected]:~] esxcli network firewall ruleset allowedip add --ip-address= --ruleset-id=sshServer


[[email protected]:~] esxcli network firewall ruleset allowedip add -i= -r=sshServer

To remove specified IP address

[[email protected]:~] esxcli network firewall ruleset allowedip remove --ip-address= -r=sshServer

List rules associated with a particular service’s ruleset

[[email protected]:~] esxcli network firewall ruleset rule list | grep sshServer

sshServer                 Inbound    TCP       Dst                22        22


[[email protected]:~] esxcli network firewall ruleset rule list -r "sshServer"

sshServer                 Inbound    TCP       Dst                22        22

If you want to check all allowed IP address for all the services. Use below command.

[[email protected]:~] esxcli network firewall ruleset allowedip listRuleset                   Allowed IP Addresses  ------------------------------------------------sshServer       ,,

Ruleset                   Allowed IP Addresses

sshServer       ,,
sshClient                 All                                                                                                                                          

nfsClient                 All        

List all the rulesets for which the allowedip list has been enabled

[[email protected]:~] esxcli network firewall ruleset allowedip list | grep -v "All"

List the default firewall rules

[[email protected]:~] esxcli network firewall ruleset list

Name                      Enabled

------------------------  -------

sshServer                    true

sshClient                    true

nfsClient                   false

nfs41Client                 false

dhcp                         true

dns                          true

snmp                         true

ntpClient                   false

CIMHttpServer                true

CIMHttpsServer               true

CIMSLP                       true

iSCSI                        true

vpxHeartbeats                true



GitHub Commands Tutorial for Beginners

GitHub is a code hosting platform for version control and collaboration. It lets you and others work together on projects from anywhere. GitHub has become the industry-standard version control and publishing the platform for web developers. It also provides command line tool access control and several collaboration features, such as wikis and basic task management tools for every project. This example GitHub commands tutorial for beginners will help to improve.

Example GitHub Commands

Show helpful guides that come with Git

git help -g

Search change by content

git log -S'<a term in the source>'

Sync with remote, overwrite local changes

git fetch origin && git reset --hard origin/master && git clean -f -d

List of all files till a commit

git ls-tree --name-only -r <commit-ish>

Git reset first commit

git update-ref -d HEAD

List all the conflicted files

git diff --name-only --diff-filter=U

List of all files changed in a commit

git diff-tree --no-commit-id --name-only -r <commit-ish>

Unstaged changes since last commit

git diff

Changes staged for commit

git diff --cached


git diff --staged

Show both staged and unstaged changes

git diff HEAD

List all branches that are already merged into master

git branch --merged master

Quickly switch to the previous branch

git checkout -


git checkout @{-1}

Remove branches that have already been merged with master

git branch --merged master | grep -v '^\*' | xargs -n 1 git branch -d


git branch --merged master | grep -v '^\*\| master' | xargs -n 1 git branch -d # will not delete master if master is not checked out

List all branches and their upstream, as well as last commit on branch

git branch -vv

Track upstream branch

git branch -u origin/mybranch

Delete local branch

git branch -d <local_branchname>

Delete remote branch

git push origin --delete <remote_branchname>


git push origin :<remote_branchname>

Delete local tag

git tag -d <tag-name>

Delete remote tag

git push origin :refs/tags/<tag-name>

Undo local changes with the last content in head

git checkout -- <file_name>

Revert: Undo a commit by creating a new commit

git revert <commit-ish>

Reset: Discard commits, advised for private branch

git reset <commit-ish>

Reword the previous commit message

git commit -v --Werner

See commit history for just the current branch

git cherry -v master

Werner author.

git commit --Werner --author='Author Name <[email protected]>'

Reset author, after author has been changed in the global config.

git commit --Werner --reset-author --no-edit

Changing a remote’s URL

git remote set-url origin <URL>

Get list of all remote references

git remote


git remote show

Get list of all local and remote branches

git branch -a

Get only remote branches

git branch -r

Stage parts of a changed file, instead of the entire file

git add -p

Get git bash completion

curl > ~/.git-completion.bash && echo '[ -f ~/.git-completion.bash ] && . ~/.git-completion.bash' >> ~/.bashrc

What changed since two weeks?

git log --no-merges --raw --since='2 weeks ago'


git whatchanged --since='2 weeks ago'

See all commits made since forking from master

git log --no-merges --stat --reverse master..

Pick commits across branches using cherry-pick

git checkout <branch-name> && git cherry-pick <commit-ish>

Find out branches containing commit-hash

git branch -a --contains <commit-ish>


git branch --contains <commit-ish>

Git Aliases

git config --global alias.<handle> <command> 
git config --global status

Saving current state of tracked files without commiting

git stash


git stash save

Saving current state of unstaged changes to tracked files

git stash -k


git stash --keep-index
git stash save --keep-index

Saving current state including untracked files

git stash -u


git stash save -u
git stash save --include-untracked

Saving current state with message

git stash save <message>

Saving current state of all files (ignored, untracked, and tracked)

git stash -a


git stash --all
git stash save --all

Show list of all saved stashes

git stash list

Apply any stash without deleting from the stashed list

git stash apply <[email protected]{n}>

Apply last stashed state and delete it from stashed list

git stash pop


git stash apply [email protected]{0} && git stash drop [email protected]{0}

Delete all stored stashes

git stash clear


git stash drop <[email protected]{n}>

Grab a single file from a stash

git checkout <[email protected]{n}> -- <file_path>


git checkout [email protected]{0} -- <file_path>

Show all tracked files

git ls-files -t

Show all untracked files

git ls-files --others

Show all ignored files

git ls-files --others -i --exclude-standard

Create new working tree from a repository (git 2.5)

git worktree add -b <branch-name> <path> <start-point>

Create new working tree from HEAD state

git worktree add --detach <path> HEAD

Untrack files without deleting

git rm --cached <file_path>


git rm --cached -r <directory_path>

Before deleting untracked files/directory, do a dry run to get the list of these files/directories

git clean -n

Forcefully remove untracked files

git clean -f

Forcefully remove untracked directory

git clean -f -d


git clean -df

Update all the submodules

git submodule foreach git pull


git submodule update --init --recursive
git submodule update --remote

Show all commits in the current branch yet to be merged to master

git cherry -v master


git cherry -v master <branch-to-be-merged>

Rename a branch

git branch -m <new-branch-name>


git branch -m [<old-branch-name>] <new-branch-name>

Rebases ‘feature’ to ‘master’ and merges it in to master

git rebase master feature && git checkout master && git merge -

Archive the master branch

git archive master --format=zip

Modify previous commit without modifying the commit message

git add --all && git commit --Werner --no-edit

Prunes references to remote branches that have been deleted in the remote.

git fetch -p


git remote prune origin

Retrieve the commit hash of the initial revision.

git rev-list --reverse HEAD | head -1


git rev-list --max-parents=0 HEAD
git log --pretty=oneline | tail -1 | cut -c 1-40
git log --pretty=oneline --reverse | head -1 | cut -c 1-40

Visualize the version tree.

git log --pretty=oneline --graph --decorate --all


gitk --all

Deploying git tracked subfolder to gh-pages

git subtree push --prefix subfolder_name origin gh-pages

Adding a project to repo using subtree

git subtree add --prefix=<directory_name>/<project_name> --squash [email protected]:<username>/<project_name>.git master

Get latest changes in your repo for a linked project using subtree

git subtree pull --prefix=<directory_name>/<project_name> --squash [email protected]:<username>/<project_name>.git master

Export a branch with history to a file.

git bundle create <file> <branch-name>

Import from a bundle

git clone repo.bundle <repo-dir> -b <branch-name>

Get the name of current branch.

git rev-parse --abbrev-ref HEAD

Ignore one file on commit (e.g. Changelog).

git update-index --assume-unchanged Changelog; git commit -a; git update-index --no-assume-unchanged Changelog

Stash changes before rebasing

git rebase --autostash

Fetch pull request by ID to a local branch

git fetch origin pull/<id>/head:<branch-name>


git pull origin pull/<id>/head:<branch-name>

Show the most recent tag on the current branch.

git describe --tags --abbrev=0

Show inline word diff.

git diff --word-diff

Show changes using common diff tools.

git difftool -t <commit1> <commit2> <path>

Don’t consider changes for tracked file.

git update-index --assume-unchanged <file_name>

Undo assume-unchanged.

git update-index --no-assume-unchanged <file_name>

Clean the files from .gitignore.

git clean -X -f

Restore deleted file.

git checkout <deleting_commit>^ -- <file_path>

Restore file to a specific commit-hash

git checkout <commit-ish> -- <file_path>

Always rebase instead of merge on pull.

git config --global pull.rebase true


#git < 1.7.9
git config --global branch.autosetuprebase always

List all the alias and configs.

git config --list

Make git case sensitive.

git config --global core.ignorecase false

Add custom editors.

git config --global core.editor '$EDITOR'

Auto correct typos.

git config --global help.autocorrect 1

Check if the change was a part of a release.

git name-rev --name-only <SHA-1>

Dry run. (any command that supports dry-run flag should do.)

git clean -fd --dry-run

Marks your commit as a fix of a previous commit.

git commit --fixup <SHA-1>

Squash fixup commits normal commits.

git rebase -i --autosquash

Skip staging area during commit.

git commit --only <file_path>

Interactive staging.

git add -i

List ignored files.

git check-ignore *

Status of ignored files.

git status --ignored

Commits in Branch1 that are not in Branch2

git log Branch1 ^Branch2

List n last commits

git log -<n>


git log -n <n>

Reuse recorded resolution, record and reuse previous conflicts resolutions.

git config --global rerere.enabled 1

Open all conflicted files in an editor.

git diff --name-only | uniq | xargs $EDITOR

Count unpacked number of objects and their disk consumption.

git count-objects --human-readable

Prune all unreachable objects from the object database.

git gc --prune=now --aggressive

Instantly browse your working repository in gitweb.

git instaweb [--local] [--httpd=<httpd>] [--port=<port>] [--browser=<browser>]

View the GPG signatures in the commit log

git log --show-signature

Remove entry in the global config.

git config --global --unset <entry-name>

Checkout a new branch without any history

git checkout --orphan <branch_name>

Extract file from another branch.

git show <branch_name>:<file_name>

List only the root and merge commits.

git log --first-parent

Change previous two commits with an interactive rebase.

git rebase --interactive HEAD~2

List all branch is WIP

git checkout master && git branch --no-merged

Find guilty with binary search

git bisect start # Search start 
git bisect bad # Set point to bad commit 
git bisect good v2.6.13-rc2 # Set point to good commit|tag 
git bisect bad # Say current state is bad 
git bisect good # Say current state is good 
git bisect reset # Finish search

Bypass pre-commit and commit-msg githooks

git commit --no-verify

List commits and changes to a specific file (even through renaming)

git log --follow -p -- <file_path>

Clone a single branch

git clone -b <branch-name> --single-branch

Create and switch new branch

git checkout -b <branch-name>


git branch <branch-name> && git checkout <branch-name>

Ignore file mode changes on commits

git config core.fileMode false

Turn off git colored terminal output

git config --global color.ui false

Specific color settings

git config --global <specific command e.g branch, diff> <true, false or always>

Show all local branches ordered by recent commits

git for-each-ref --sort=-committerdate --format='%(refname:short)' refs/heads/

Find lines matching the pattern (regex or string) in tracked files

git grep --heading --line-number 'foo bar'

Clone a shallow copy of a repository

git clone --depth 1

Search Commit log across all branches for given text

git log --all --grep='<given-text>'

Get first commit in a branch (from master)

git log master..<branch-name> --oneline | tail -1

Unstaging Staged file

git reset HEAD <file-name>

Force push to Remote Repository

git push -f <remote-name> <branch-name>

Adding Remote name

git remote add <remote-nickname> <remote-url>

Show the author, time and last revision made to each line of a given file

git blame <file-name>

Group commits by authors and title

git shortlog

Forced push but still ensure you don’t overwrite other’s work

git push --force-with-lease <remote-name> <branch-name>

Show how many lines does an author contribute

git log --author='_Your_Name_Here_' --pretty=tformat: --numstat | gawk '{ add += <!-- @doxie.inject start -->; subs += <!-- @doxie.inject end -->; loc += <!-- @doxie.inject start --> - <!-- @doxie.inject end --> } END { printf "added lines: %s removed lines: %s total lines: %s
", add, subs, loc }' -


git log --author='_Your_Name_Here_' --pretty=tformat: --numstat | awk '{ add += <!-- @doxie.inject start -->; subs += <!-- @doxie.inject end -->; loc += <!-- @doxie.inject start --> - <!-- @doxie.inject end --> } END { printf "added lines: %s, removed lines: %s, total lines: %s
", add, subs, loc }' - # on Mac OSX

Revert: Reverting an entire merge

git revert -m 1 <commit-ish>

Number of commits in a branch

git rev-list --count <branch-name>

Alias: git undo

git config --global alias.undo '!f() { git reset --hard $(git rev-parse --abbrev-ref HEAD)@{${1-1}}; }; f'

Add object notes

git notes add -m 'Note on the previous commit....'

Show all the git-notes

git log --show-notes='*'

Apply commit from another repository

git --git-dir=<source-dir>/.git format-patch -k -1 --stdout <SHA1> | git am -3 -k

Specific fetch reference

git fetch origin master:refs/remotes/origin/mymaster

Find common ancestor of two branches

diff -u <(git rev-list --first-parent BranchA) <(git rev-list --first-parent BranchB) | sed -ne 's/^ //p' | head -1

List unpushed git commits

git log --branches --not --remotes


git log @{u}..
git cherry -v

Add everything, but whitespace changes

git diff --ignore-all-space | git apply --cached

Edit [local/global] git config

git config [--global] --edit

blame on certain range

git blame -L <start>,<end>

Show a Git logical variable.

git var -l | <variable>

Preformatted patch file.

git format-patch -M upstream..topic

Get the repo name.

git rev-parse --show-toplevel

logs between date range

git log --since='FEB 1 2017' --until='FEB 14 2017'

Exclude author from logs

git log --perl-regexp --author='^((?!excluded-author-regex).*)

Generates a summary of pending changes

git request-pull v1.0 https://git.ko.xz/project master:for-linus

List references in a remote repository

git ls-remote git://

Backup untracked files.

git ls-files --others -i --exclude-standard | xargs zip

List all git aliases

git config -l | grep alias | sed 's/^alias\.//g'


git config -l | grep alias | cut -d '.' -f 2

Show git status short

git status --short --branch

Checkout a commit prior to a day ago

git checkout [email protected]{yesterday}


You can use this URL to get more details and Tips.