# admin tools

* [encryption](#encryption)
  * [gpg](#gpg)
    * [basic knowledge](#basic-knowledge)
    * [create new key](#create-new-key)
    * [list keys](#list-keys)
    * [remove keys](#remove-keys)
    * [export/import keys](#exportimport-keys)
    * [usage](#usage)
  * [pass](#pass)
    * [env](#env)
    * [insert](#insert)
    * [generate](#generate)
    * [remove](#remove)
    * [advanced usage](#advanced-usage)
    * [plugins](#plugins)
  * [OTP](#otp)
    * [pass-otp](#pass-otp)
  * [PGP](#pgp)
  * [passwd](#passwd)
* [network tools](#network-tools)
  * [`vnstat`](#vnstat)
  * [`ipcalc`](#ipcalc)
  * [`iostat`](#iostat)
  * [`tcpdump`](#tcpdump)
  * [`dstat`](#dstat)
  * [strace](#strace)
  * [`dtruss`](#dtruss)
  * [sar](#sar)
  * [netcat](#netcat)
  * [`ip`](#ip)
  * [datadog](#datadog)
* [others](#others)

{% hint style="info" %}
> references:
>
> * [20 Command Line Tools to Monitor Linux Performance](http://www.tecmint.com/command-line-tools-to-monitor-linux-performance/)
> * [20 Linux System Monitoring Tools Every SysAdmin Should Know](http://www.cyberciti.biz/tips/top-linux-monitoring-tools.html)
> * [Top 25 Best Linux Performance Monitoring and Debugging Tools](http://thegeekstuff.com/2011/12/linux-performance-monitoring-tools/)
> * [http://www.thegeekstuff.com/2010/12/50-unix-linux-sysadmin-tutorials](http://www.thegeekstuff.com/2010/12/50-unix-linux-sysadmin-tutorials/)
> * [16 commands to check hardware information on Linux](http://www.binarytides.com/linux-commands-hardware-info/)
> * [Best UNIX shell-based tools](https://gist.github.com/mbbx6spp/1429161)
> * [\* alebcay/awesome-shell](https://github.com/alebcay/awesome-shell/tree/master)
>   * [\* zh-cn](https://github.com/alebcay/awesome-shell/blob/master/README_ZH-CN.md)
>   * [nosarthur/awesome-shell](https://github.com/nosarthur/awesome-shell)
> * [\* rockerBOO/awesome-neovim](https://github.com/rockerBOO/awesome-neovim)
> * [jlevy/the-art-of-command-line](https://github.com/jlevy/the-art-of-command-line)
> * [Learn Enough Command Line to Be Dangerous](https://www.learnenough.com/command-line-tutorial/basics)
> * [Shell Style Guide](https://google.github.io/styleguide/shellguide.html)
> * [Use Bash Strict Mode (Unless You Love Debugging)](http://redsymbol.net/articles/unofficial-bash-strict-mode/)
> * others
>   * [bayandin/awesome-awesomeness](https://github.com/bayandin/awesome-awesomeness)
>   * [emijrp/awesome-awesome](https://github.com/emijrp/awesome-awesome)
>   * [kahun/awesome-sysadmin](https://github.com/kahun/awesome-sysadmin)
> * [My Minimalist Over-powered Linux Setup Guide](https://medium.com/@jonyeezs/my-minimal-over-powered-linux-setup-guide-710931efb75b)
> * [\* devynspencer/cute\_commands.sh](https://gist.github.com/devynspencer/cfdce35b3230e72214ef)
{% endhint %}

## encryption

### gpg

> \[!NOTE|label:references:]
>
> * [\* The GNU Privacy Handbook](https://www.gnupg.org/gph/en/manual.html)
> * [\* The GNU Privacy Guard Manual](https://www.gnupg.org/documentation/manuals/gnupg/GPG-Configuration-Options.html)
> * [GPG入门教程](https://www.ruanyifeng.com/blog/2013/07/gpg.html)
> * [GPG(GnuPG)入门](https://www.cnblogs.com/time-is-life/p/9668999.html)
> * [FlowCrypt: PGP Encryption for Gmail](https://flowcrypt.com/)

#### basic knowledge

> \[!NOTE|label:references:]
>
> * to show `--dump-options`: `gpg --dump-options`

*   [letters indicating](https://www.gnupg.org/documentation/manuals/gnupg/GPG-Configuration-Options.html)

    > \[!TIP|label:references:]
    >
    > * [简明 GPG 概念](https://zhuanlan.zhihu.com/p/137801979)
    > * GPG 密钥的能力中， \[C]、\[S]、\[A] 均属于签名方案，只有 \[E] 是加密方案
    > * [The GNU Privacy Guard Manual : 4.2.1 How to change the configuration](https://www.gnupg.org/documentation/manuals/gnupg/GPG-Configuration-Options.html)
    > * [OpenPGP Message Format : 5.2.3.21. Key Flags](https://www.rfc-editor.org/rfc/rfc4880#section-5.2.3.21)
    > * [How are the GPG usage flags defined in the key details listing?](https://unix.stackexchange.com/a/230859/29178)
    > * [Anatomy of a GPG Key](https://davesteele.github.io/gpg/2014/09/20/anatomy-of-a-gpg-key/)

    | LETTER | MEANING       | flag             | CONSTANT            | COMMENTS                       |
    | ------ | ------------- | ---------------- | ------------------- | ------------------------------ |
    | `[C]`  | Certification | `0x01`           | PUBKEY\_USAGE\_CERT | 认证其他秘钥/给其他证书签名                 |
    | `[S]`  | Signing       | `0x02`           | PUBKEY\_USAGE\_SIG  | 签名,如给文件添加数字签名, 给 git commit 签名 |
    | `[A]`  | Authenticate  | `0x20`           | PUBKEY\_USAGE\_AUTH | 身份验证, 如 ssh 登录                 |
    | `[E]`  | Encryption    | `0x04` or `0x08` | PUBKEY\_USAGE\_ENC  | 加密, 如给文件加密, 给邮件加密              |

#### create new key

> \[!NOTE|label:references:]
>
> * [Generating GPG Keys](https://www.files.com/docs/encryption/gpg-pgp/generating-gpg-keys)
> * [How to create GPG keypairs](https://www.redhat.com/sysadmin/creating-gpg-keypairs)
> * [Generating a new GPG key](https://docs.github.com/en/authentication/managing-commit-signature-verification/generating-a-new-gpg-key)

```bash
$ gpg --full-generate-key
```

*   [or](https://superuser.com/a/1360557/112396)

    ```bash
    $ gpg --batch --gen-key <<EOF
    %no-protection
    Key-Type:1
    Key-Length:2048
    Subkey-Type:1
    Subkey-Length:2048
    Name-Real: <John Doe>
    Name-Email: <john.doe@domain.com>
    Expire-Date:0
    EOF
    ```

#### list keys

*   secret keys

    ```bash
    $ gpg --list-secret-keys --keyid-format=long
    gpg: checking the trustdb
    gpg: marginals needed: 3  completes needed: 1  trust model: pgp
    gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
    [keyboxd]
    ---------
    sec   ed25519/505104FC7CD6CA33 2024-05-08 [SC]
          00D2F41050BF7D9BE6B27545505104FC7CD6CA33
    uid                 [ultimate] marslo <marslo.jiao@gmail.com>
    ssb   cv25519/188C36434D6B9F66 2024-05-08 [E]
    ```
*   public keys

    ```bash
    $ gpg --list-public-keys --keyid-format=long
    [keyboxd]
    ---------
    pub   ed25519/5C0980808D968494 2024-05-08 [SC]
          6AADCD68E268DEF623C4DD7E5C0980808D968494
    uid                 [ultimate] marslo <marslo.jiao@gmail.com>
    sub   cv25519/F065036D0FF76ABA 2024-05-08 [E]
    ```
*   list KEYID

    ```bash
    $ gpg --list-keys --with-colons |
          awk -F: '$1 == "pub" && ($2 == "e" || $2 == "r" || $2 == "u") { print $5 }'
    ```
*   with fingerprint

    ```bash
    $ gpg --list-secret-keys --with-colons --fingerprint
    sec:u:255:22:5C0980808D968494:1715138996:::u:::scESC:::+::ed25519:::0:
    fpr:::::::::6AADCD68E268DEF623C4DD7E5C0980808D968494:
    grp:::::::::DA2F273B9FCDBCE44E8F5B1590CC29F774C557A5:
    uid:u::::1715138996::689D1C164C7C46F315D0FF60C5CDE6E509C6D853::marslo <marslo.jiao@gmail.com>::::::::::0:
    ssb:u:255:18:F065036D0FF76ABA:1715138996::::::e:::+::cv25519::
    fpr:::::::::B6550514914F4E14976755BBF065036D0FF76ABA:
    grp:::::::::C55CD6EE8B06EC939090352069AB9D37CFA0C7FA:

    # list fingerprint only
    $ gpg --list-keys --with-colons | awk -F: '$1 == "fpr" { print $10 }'
    6AADCD68E268DEF623C4DD7E5C0980808D968494
    B6550514914F4E14976755BBF065036D0FF76ABA

    # or
    $ gpg --list-secret-keys --with-colons --fingerprint | sed -n 's/^fpr:::::::::\([[:alnum:]]\+\):/\1/p'
    6AADCD68E268DEF623C4DD7E5C0980808D968494
    B6550514914F4E14976755BBF065036D0FF76ABA
    ```

#### remove keys

*   remove all keys

    ```bash
    $ gpg --yes --delete-secret-and-public-key "marslo"
    gpg (GnuPG) 2.4.5; Copyright (C) 2024 g10 Code GmbH
    This is free software: you are free to change and redistribute it.
    There is NO WARRANTY, to the extent permitted by law.

    sec  ed25519/133597088DEF3074 2024-05-08 marslo (marslo) <marslo.jiao@gmail.com>

    Delete this key from the keyring? (y/N) y
    This is a secret key! - really delete? (y/N) y

    pub  ed25519/133597088DEF3074 2024-05-08 marslo (marslo) <marslo.jiao@gmail.com>
    Delete this key from the keyring? (y/N) y
    ```
*   [or via `--batch`](https://superuser.com/a/1631427/112396)

    ```bash
    $ gpg --list-keys --with-colons \
        | awk -F: '$1 == "pub" && ($2 == "e" || $2 == "r" || $2 == "u") { print $5 }' \
        | xargs gpg --batch --yes --delete-secret-and-public-key
    ```
*   [or via fingerprint](https://superuser.com/a/1192732/112396)

    ```bash
    $ gpg --fingerprint --with-colons ${GPG_KEY} |\
          grep "^fpr" |\
          sed -n 's/^fpr:::::::::\([[:alnum:]]\+\):/\1/p' |\
          xargs gpg --batch --delete-secret-keys
    ```

#### export/import keys

> \[!NOTE|label:references:]
>
> * [How to export a GPG private key and public key to a file](https://unix.stackexchange.com/a/482559/29178)
> * [Moving GPG Keys Privately](https://vhs.codeberg.page/post/moving-gpg-keys-privately/)

**export**

*   export public key

    ```bash
    $ gpg --output public.pgp --armor --export <KEYID>
    ```

    *   check content

        ```bash
        $ gpg --armor --export <KEYID>

        # i.e.:
        $ gpg --armor --export marslo
        -----BEGIN PGP PUBLIC KEY BLOCK-----
        ...
        -----END PGP PUBLIC KEY BLOCK-----
        ```
*   export secret key

    ```bash
    $ gpg --output private.pgp --armor --export-secret-key <KEYID>
    # or
    $ gpg -o ~/private.asc --export-secret-key <KEYID>
    ```

    *   [export and ssh](https://unix.stackexchange.com/a/618702/29178)

        ```bash
        $ gpg --export-secret-key SOMEKEYID | ssh othermachine gpg --import
        ```
    *   [more](https://unix.stackexchange.com/a/618702/29178)

        ```bash
        $ gpg --output public.gpg --export SOMEKEYID && \
        $ gpg --output - --export-secret-key SOMEKEYID |\
              cat public.gpg - |\
              gpg --armor --output keys.asc --symmetric --cipher-algo AES256
        ```
    *   check content

        ```bash
        $ gpg --armor --export-secret-keys <KEYID>

        # i.e.:
        $ gpg --armor --export-secret-keys marslo
        -----BEGIN PGP PRIVATE KEY BLOCK-----
        ...
        -----END PGP PRIVATE KEY BLOCK-----
        ```
*   backup keys

    ```bash
    $ gpg --output backupkeys.pgp --armor --export-secret-keys --export-options export-backup <KEYID>
    # or
    $ gpg --output backupkeys.pgp --armor --export --export-options export-backup <KEYID>
    ```

**import**

> \[!NOTE|label:references:]
>
> * [How to import secret keys into GPG keychain](https://unix.stackexchange.com/a/230859/29178)
> * [pass and gpg: No public key](https://unix.stackexchange.com/a/232341/29178)
> * [How to import secret gpg key (copied from one machine to another)?](https://unix.stackexchange.com/a/184952/29178)

```bash
# import private key
$ gpg --import private.pgp
gpg: /home/marslo/.gnupg/trustdb.gpg: trustdb created
gpg: key 5C0980808D968494: public key "marslo <marslo.jiao@gmail.com>" imported
gpg: key 5C0980808D968494: secret key imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg:       secret keys read: 1
gpg:   secret keys imported: 1

# list keys
$ gpg --list-keys
/home/marslo/.gnupg/pubring.kbx
-------------------------------
pub   ed25519 2024-05-08 [SC]
      6AADCD68E268DEF623C4DD7E5C0980808D968494
uid           [ unknown] marslo <marslo.jiao@gmail.com>
sub   cv25519 2024-05-08 [E]

# trust
$ gpg --edit-key 6AADCD68E268DEF623C4DD7E5C0980808D968494 trust quit
  1 = I don't know or won't say
  2 = I do NOT trust
  3 = I trust marginally
  4 = I trust fully
  5 = I trust ultimately
  m = back to the main menu

gpg> Your decision? 5
gpg> Do you really want to set this key to ultimate trust? (y/N) y

# check key again
$ gpg --list-keys
gpg: checking the trustdb
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
/home/marslo/.gnupg/pubring.kbx
-------------------------------
pub   ed25519 2024-05-08 [SC]
      6AADCD68E268DEF623C4DD7E5C0980808D968494
uid           [ultimate] marslo <marslo.jiao@gmail.com>
sub   cv25519 2024-05-08 [E]
```

*   import publid key

    ```bash
    # import public key
    $ gpg --import public.pgp
    gpg: key 5C0980808D968494: "marslo <marslo.jiao@gmail.com>" not changed
    gpg: Total number processed: 1
    gpg:              unchanged: 1
    ```
*   trust key

    ```bash
    # verify available
    $ gpg --edit-key <KEYID>

    # trust
    $ gpg --edit-key <KEYID>
    gpg> trust
    gpg> save
    gpg> quit
    ```
*   recover from backup keys

    ```bash
    $ gpg --import-options restore --import backupkeys.pgp
    ```

#### usage

> \[!NOTE|label:references:]
>
> * [GPG使用方法总结（密钥管理，加解密文件）](https://blog.csdn.net/vic_qxz/article/details/127225478)

### pass

> \[!NOTE]
>
> * [pass: the standard unix password manager](https://www.passwordstore.org/)
> * [git repo: password-store](https://git.zx2c4.com/password-store/)
> * [video: How to Use Pass Which Is a Command Line Password Manager](https://www.youtube.com/watch?v=w34xAnNdliE)
> * [How to Use Pass Which Is a Command Line Password Manager](https://nickjanetakis.com/blog/how-to-use-pass-which-is-a-command-line-password-manager)
> * [archlinux: pass](https://wiki.archlinux.org/title/Pass)
> * [compatible clients](https://www.passwordstore.org/#other)
> * [Clever uses of pass, the Unix password manager](https://vitalyparnas.com/guides/pass/#generate)
> * [Configuring Pass, the Standard Unix Password Manager](https://ryan.himmelwright.net/post/setting-up-pass/)

#### env

> \[!NOTE|label:references:]
>
> * [completion](https://git.zx2c4.com/password-store/tree/src/completion)
> * [environment variable](https://manpages.ubuntu.com/manpages/noble/man1/pass.1.html#environment%20variables)
>   * `PASSWORD_STORE_DIR`
>   * `PASSWORD_STORE_KEY`
>   * `PASSWORD_STORE_GENERATED_LENGTH`
>   * `PASSWORD_STORE_CHARACTER_SET`
>   * `PASSWORD_STORE_CHARACTER_SET_NO_SYMBOLS`
>   * `PASSWORD_STORE_CLIP_TIME`
>   * `PASSWORD_STORE_EXTENSIONS_DIR`
>   * `PASSWORD_STORE_ENABLE_EXTENSIONS`
>   * `PASSWORD_STORE_SIGNING_KEY`

```bash
$ export PASSWORD_STORE_DIR=~/.password-store
```

*   install

    ```bash
    # osx
    $ brew install pass

    # ubuntu/debian
    $ sudo apt-get install pass

    # fedora/rhel
    $ sudo yum install pass
    ```
*   init

    > \[!TIP|label:references:]
    >
    > * [How to manage Linux passwords with the pass command](https://www.redhat.com/sysadmin/management-password-store)
    > * [I try to add passwords to the "pass" password manager. But my attempts fail with "no public key" GPG errors. Why?](admintools)
    > *   to avoid the issue like:
    >
    >     ```bash
    >     $ pass generate test 30
    >     gpg: marslo: skipped: No public key
    >     gpg: [stdin]: encryption failed: No public key
    >     Password encryption aborted.
    >     ```

    ```bash
    $ gpg --full-generate-key
    ```

#### insert

```bash
$ pass insert <NAME>

# i.e.:
$ pass insert test
Enter password for test: abc
Retype password for test: abc
$ pass test
abc

# copy
$ pass -c test
Copied test to clipboard. Will clear in 45 seconds.
```

![pass insert](https://1999659500-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MHqOSW6on5cHbtwcSH6%2Fuploads%2Fgit-blob-dadab71b44efa90670aa1b14de9d2c7baaf19af3%2Fcmd-pass-insert.gif?alt=media)

#### generate

> \[!NOTE|label:references:]
>
> * [PASSWORD\_STORE\_CHARACTER\_SET\_NO\_SYMBOLS isn't respected](https://lists.zx2c4.com/pipermail/password-store/2018-January/003170.html)
> * [\[pass\] Provide symbol set as command line argument](https://lists.zx2c4.com/pipermail/password-store/2016-November/002429.html)
> * [How to generate secure passwords using terminal (Mac/Linux) ?](https://mnzel.medium.com/how-to-generate-secure-passwords-using-terminal-mac-linux-3e823cff3cac)
> * [default and envs](https://git.zx2c4.com/password-store/tree/src/password-store.sh)
>   * `PASSWORD_STORE_DIR=$HOME/.password-store`
>   * `PASSWORD_STORE_EXTENSIONS_DIR=${PASSWORD_STORE_DIR}/.extensions`
>   * `PASSWORD_STORE_CLIP_TIME=45`
>   * `PASSWORD_STORE_GENERATED_LENGTH=25`
>   * others:
>     * `PASSWORD_STORE_CHARACTER_SET='[:alnum:].,!?&*%_~$#^@{}[]()<>|=/\+-'`
> *   [Vim: word vs WORD](https://stackoverflow.com/a/54588479/2940319)
>
>     ![WORD VS. word](https://1999659500-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MHqOSW6on5cHbtwcSH6%2Fuploads%2Fgit-blob-4fa7f36a51477fea0dec60e8e27ef6ab30f90a09%2Fwordvsword.png?alt=media)

*   customize charset

    ```bash
    $ export PASSWORD_STORE_CHARACTER_SET='a-zA-Z0-9'
    $ yes | pass generate test 30
    The generated password for test is:
    HnD7XyeFDtOrw5oDhn22U8AjHVV9cf
    $ yes | pass generate test 30
    The generated password for test is:
    t57PYCw4r0tHSXCa4zW2DVGNuizQ1k

    $ export PASSWORD_STORE_CHARACTER_SET='a-zA-Z0-9()'
    $ yes | pass generate test 50
    The generated password for test is:
    wof1Hw92QXe(G3)MkMRp5Wx3UCMgHIpt)7ENNn(f8r(ZRcztQ1
    $ yes | pass generate test 30
    The generated password for test is:
    60m2XHtqfTsvfJT(YYV1wKlBBoOJYb
    ```
*   generate qrcode

    ```bash
    $ pass generate <name> --qrcode
    ```
*   [generate via `/dev/urandom`](https://lists.zx2c4.com/pipermail/password-store/2016-November/002429.html)

    ```bash
    $ head /dev/urandom | tr -dc 'A-Za-z0-9!@#$%^&*()' | head -c 32 && echo
    xGPqC%MeE2HU3NkH#JeA##RB^YbX49cd

    $ head /dev/urandom | tr -dc 'A-Za-z0-9!@#$%^&*()?:_-~+<=>' | head -c 32 && echo
    e?XEGaD68^FNYI5#E^aFVgv:(6_pL>!I

    $ head /dev/urandom | tr -dc 'A-Za-z0-9!"#$%&'\''()*+,-./:;<=>?@[\]^_`{|}~' | head -c 32 && echo
    +&7<o(zfE[WC30v'D[&RH~;qM-8J>oQC
    ```
*   [generate via openssl](https://www.commandlinefu.com/commands/view/4204/generate-random-password)

    ```bash
    $ openssl rand -base64 32
    DfXwoBz8UAel09qN1rR97luKy+aFuC8N0Fua+YaSW8A=

    # or: https://www.commandlinefu.com/commands/view/24565/generate-a-random-password-30-characters-long
    $ openssl rand -rand /dev/urandom -base64 32
    ```

#### remove

```bash
$ pass rm test -f
removed '/Users/marslo/.marslo/.password-store/test.gpg'
```

#### advanced usage

> \[!NOTE|label:references:]
>
> * extensions
>   * [roddhjav/pass-tomb](https://github.com/roddhjav/pass-tomb)
>   * [tadfisher/pass-otp)](https://github.com/tadfisher/pass-otp) | [pass-otp.bash.completion](https://github.com/tadfisher/pass-otp/blob/develop/pass-otp.bash.completion)
>   * [roddhjav/pass-import](https://github.com/roddhjav/pass-import)
>   * [roddhjav/pass-update](https://github.com/roddhjav/pass-update)
>   * [roddhjav/pass-audit](https://github.com/roddhjav/pass-audit)
>   * [ayushnix/pass-coffin](https://github.com/ayushnix/pass-coffin)
>   * [ayushnix/pass-tessen](https://github.com/ayushnix/pass-tessen)
> * additional tools
>   * [Pass for Alfred](https://alfred.app/workflows/chrisgrieser/pass/)

*   alfred workflow

    ```bash
    $ brew isntall --HEAD pinentry-mac

    # using pinentry-mac instead of pinentry for alfred workflow
    $ [[ -d "$HOME/.gnupg" ]] || mkdir "$HOME/.gnupg"
    $ echo "pinentry-program $(brew --prefix)/bin/pinentry-mac" > $HOME/.gnupg/gpg-agent.conf
    $ gpgconf --kill gpg-agent                           # restart the agent
    ```
*   pw

    ```bash
    pw() {
      export PASSWORD_STORE_CLIP_TIME=8
      export PASSWORD_STORE_X_SELECTION=primary
      pass -c2 $1; sleep 5; pass -c $1; sleep 5; pass otp -c $1; exit
    }
    ```
*   extend

    ```bash
    # ~/.bashrc
    $ alias passred="PASSWORD_STORE_DIR=~/.pass/red pass"
    $ alias passblue="PASSWORD_STORE_DIR=~/.pass/blue pass"

    $ cat /usr/share/bash-completion/completions/pass
    _passred(){
        PASSWORD_STORE_DIR=~/.pass/red/ _pass
    }
    complete -o filenames -o nospace -F _passred passred
    _passblue(){
        PASSWORD_STORE_DIR=~/.pass/blue/ _pass
    }
    complete -o filenames -o nospace -F _passblue passblue
    $ source /usr/share/bash-completion/completions/pass
    ```
*   git

    ```bash
    $ git config --global credential.helper /usr/bin/pass-git-helper

    $ cat ~/.gitconfig
    [github.com]
    target=dev/github

    [*.fooo-bar.*]
    target=dev/fooo-bar
    ```

    *   client

        ```bash
        # create local password store
        $ pass init <gpg key id>
        # enable management of local changes through git
        $ pass git init
        # add the the remote git repository as 'origin'
        $ pass git remote add origin user@server:~/.password-store
        # push your local pass history
        $ pass git push -u --all
        ```

#### plugins

*   pass-otp

    > \[!NOTE|label:references:]
    >
    > * [#137 Bash completion](https://github.com/tadfisher/pass-otp/issues/137)

    ```bash
    # --- install ---
    # osx
    $ brew install pass-otp
    $ brew uses --recursive --installed oath-toolkit
    pass-otp

    # --- usage ---
    ## init
    $ pass otp insert -e sandbox/otp
    Enter otpauth:// URI for sandbox/otp: otpauth://totp/totp-secret?secret=sandbox
    ## show otp code
    $ pass otp sandbox/otp
    148395
    ```

### OTP

> \[!NOTE|label:references:]
>
> * [OATH-Toolkit](https://wiki.gentoo.org/wiki/OATH-Toolkit)
> * [Use oathtool Linux command line for 2 step verification (2FA)](https://www.cyberciti.biz/faq/use-oathtool-linux-command-line-for-2-step-verification-2fa/)
> * [One-Time-Passwords using oathtool on Ubuntu 14.04(+)](https://nerdyness2012.wordpress.com/2015/01/15/one-time-passwords-using-oathtool-on-ubuntu/)

#### pass-otp

> \[!NOTE|label:references:]
>
> *   tips:
>
>     ```bash
>     $ brew which-formula oathtool
>     oath-toolkit
>
>     $ brew uses --recursive --installed oath-toolkit
>     pass-otp
>     ```

```bash
$ oathtool $(openssl rand -hex 16)
848050
```

### PGP

> \[!NOTE|label:references:]
>
> * Protecting Code Integrity with PGP
>   * [Protecting Code Integrity with PGP — Part 1: Basic Concepts and Tools](https://www.linux.com/news/protecting-code-integrity-pgp-part-1-basic-pgp-concepts-and-tools/) | [用 PGP 保护代码完整性（一）： 基本概念和工具](https://linux.cn/article-9524-1.html)
>   * [Protecting Code Integrity with PGP — Part 2: Generating Your Master Key](https://www.linux.com/news/protecting-code-integrity-pgp-part-2-generating-and-protecting-your-master-pgp-key/) | [用 PGP 保护代码完整性（二）：生成你的主密钥](https://linux.cn/article-9529-1.html)
>   * [Protecting Code Integrity with PGP — Part 3: Generating PGP Subkeys](https://www.linux.com/news/protecting-code-integrity-pgp-part-3-generating-pgp-subkeys/) | [用 PGP 保护代码完整性（三）：生成 PGP 子密钥](https://linux.cn/article-9607-1.html)
>   * [Protecting Code Integrity with PGP — Part 4: Moving Your Master Key to Offline Storage](https://www.linux.com/news/protecting-code-integrity-pgp-part-4-moving-your-master-key-offline-storage/) | [用 PGP 保护代码完整性（四）：将主密钥移到离线存储中](https://linux.cn/article-10402-1.html)
>   * [Protecting Code Integrity with PGP — Part 5: Moving Subkeys to a Hardware Device](https://www.linux.com/training-tutorials/protecting-code-integrity-pgp-part-5-moving-subkeys-hardware-device) | [用 PGP 保护代码完整性（五）：将子密钥移到一个硬件设备中](https://linux.cn/article-10415-1.html)
>   * [Protecting Code Integrity with PGP — Part 6: Using PGP with Git](https://www.linux.com/news/protecting-code-integrity-pgp-part-6-using-pgp-git/) | [用 PGP 保护代码完整性（六）：在 Git 上使用 PGP](https://linux.cn/article-10421-1.html)
>   * [Protecting Code Integrity with PGP — Part 7: Protecting Online Accounts](https://www.linux.com/news/protecting-code-integrity-pgp-part-7-protecting-online-accounts/) | [用 PGP 保护代码完整性（七）：保护在线帐户](https://linux.cn/article-10432-1.html)

### passwd

> \[!NOTE|label:references:]
>
> * [Managing Linux users with the passwd command](https://www.redhat.com/sysadmin/managing-users-passwd)

## network tools

> \[!NOTE|label:see also:]
>
> * [iMarslo : linux/network](https://github.com/marslo/ibook/blob/marslo/docs/linux/network.html)

### `vnstat`

![vnstat](https://1999659500-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MHqOSW6on5cHbtwcSH6%2Fsync%2F7f1fb48f612114d27bbbea24438aecb96eabfe34.png?generation=1600788049118261\&alt=media)

```bash
$ vnstat -l 1 -i en7
Monitoring en7...    (press CTRL-C to stop)

   rx:     4.10 kbit/s   21.00 KiB          tx:         0 bit/s   6.00 KiB^C

 en7  /  traffic statistics
                           rx         |       tx
--------------------------------------+------------------
  bytes                    21.00 KiB  |        6.00 KiB
--------------------------------------+------------------
          max           53.25 kbit/s  |    12.29 kbit/s
      average           17.20 kbit/s  |     4.92 kbit/s
          min                0 bit/s  |         0 bit/s
--------------------------------------+------------------
  packets                         60  |              52
--------------------------------------+------------------
          max                 15 p/s  |          16 p/s
      average                  6 p/s  |           5 p/s
          min                  2 p/s  |           0 p/s
--------------------------------------+------------------
  time                    10 seconds
```

### `ipcalc`

![ipcalc](https://1999659500-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MHqOSW6on5cHbtwcSH6%2Fsync%2F7bc463e7f19b14d40eb848614ff5e6082c8f099c.png?generation=1600788048818370\&alt=media)

```bash
$ ipcalc 10.25.130.2/23
Address:   10.25.130.2          00001010.00011001.1000001 0.00000010
Netmask:   255.255.254.0 = 23   11111111.11111111.1111111 0.00000000
Wildcard:  0.0.1.255            00000000.00000000.0000000 1.11111111
=>
Network:   10.25.130.0/23       00001010.00011001.1000001 0.00000000
HostMin:   10.25.130.1          00001010.00011001.1000001 0.00000001
HostMax:   10.25.131.254        00001010.00011001.1000001 1.11111110
Broadcast: 10.25.131.255        00001010.00011001.1000001 1.11111111
Hosts/Net: 510                   Class A, Private Internet

$ ipcalc 10.25.131.1/23
Address:   10.25.131.1          00001010.00011001.1000001 1.00000001
Netmask:   255.255.254.0 = 23   11111111.11111111.1111111 0.00000000
Wildcard:  0.0.1.255            00000000.00000000.0000000 1.11111111
=>
Network:   10.25.130.0/23       00001010.00011001.1000001 0.00000000
HostMin:   10.25.130.1          00001010.00011001.1000001 0.00000001
HostMax:   10.25.131.254        00001010.00011001.1000001 1.11111110
Broadcast: 10.25.131.255        00001010.00011001.1000001 1.11111111
Hosts/Net: 510                   Class A, Private Internet
```

### `iostat`

```bash
$ iostat
              disk0       cpu    load average
    KB/t  tps  MB/s  us sy id   1m   5m   15m
   19.85   37  0.72   3  1 96  1.78 1.90 1.69
```

### `tcpdump`

> \[!NOTE|label:references:]
>
> * [\* Tcpdump](https://www.kancloud.cn/pshizhsysu/linux/1799754)

```bash
$ sudo tcpdump -A -i en7
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on en7, link-type EN10MB (Ethernet), capture size 262144 bytes
00:33:02.787671 IP 10.25.130.117.53629 > a23-43-240-92.deploy.static.akamaitechnologies.com.https: Flags [.], ack 697481089, win 2048, length 0
E..(....@...
..u.+.\.}..r...)...P...:...
00:33:02.790119 IP 10.25.130.117.51541 > sh-vdc01.mycompany.com.domain: 53089+ PTR? 92.240.43.23.in-addr.arpa. (43)
E..GP....._.
..u
&t..U.5.3...a...........92.240.43.23.in-addr.arpa.....
00:33:02.812866 ARP, Request who-has gw-voice-idf.cdu-cn.mycompany.com tell gw-vg224-idf.cdu-cn.mycompany.com, length 46
....
....
13 packets captured
25 packets received by filter
0 packets dropped by kernel
```

*   [or](https://superuser.com/a/1567926/112396)

    ```bash
    $ sudo tcpdump -n -i any src or dst target.ip.address [ -v ]

    # i.e.
    $ sudo tcpdump -n -i any src or dst git.domain.com -v
    tcpdump: data link type PKTAP
    tcpdump: listening on any, link-type PKTAP (Apple DLT_PKTAP), snapshot length 524288 bytes
    00:02:55.698822 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 52)
        10.25.130.104.63447 > 10.69.78.140.29418: Flags [F.], cksum 0x8fe0 (correct), seq 2566890566, ack 4019765769, win 2058, options [nop,nop,TS val 1955309758 ecr 154499413], length 0
    ```

### `dstat`

![dstat](https://1999659500-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MHqOSW6on5cHbtwcSH6%2Fsync%2F0fb33cf0364850b630f07651176668a0bf91879a.png?generation=1600788049447429\&alt=media)

### strace

> \[!NOTE|label:references:]
>
> * [I have a tab completion that hangs, is it possible to use strace to find out what is going on?](https://unix.stackexchange.com/a/525582/29178)
> * [Resolve nested aliases to their source commands](https://unix.stackexchange.com/a/441389/29178)
> * [What's the difference between <<, <<< and < < in bash?](https://askubuntu.com/a/678919)

| LINUX                              | MACOS                                                        | COMPARISON                   |
| ---------------------------------- | ------------------------------------------------------------ | ---------------------------- |
| `strace`                           | `dtruss`/`dtrace`                                            | System Call Tracking Tool    |
| `ltrace`                           | `dyldtrace`                                                  | Dynamic Link Library Tracing |
| Flexible                           | Limited by System Integrity Protection                       | Kernel Module Support        |
| Regular users can partially use it | Most features require root access or `CSRUTIL` configuration | Permission Requirements      |
| high                               | Reliance on BSD-specific syntax                              | Script Portability           |

```bash
$ ... run cmd ...

# or
$ pid=$(echo ??)
$ sudo strace -fp ${pid} -o log

# or
$ sudo -v
$ sudo strace -fp $$ -o log &

# -- more --
$ set -o functrace xtrace
$ PS4=' ${BASH_SOURCE}:$FUNCNAME:$LINENO: '
```

*   [intercept stdout/stderr of another process](https://www.commandlinefu.com/commands/view/5410/intercept-stdoutstderr-of-another-process)

    ```bash
    $ strace -ff -e trace=write -e write=1,2 -p SOME_PID

    # https://www.commandlinefu.com/commands/view/5450/intercept-stdoutstderr-of-another-process
    $ strace -ff -e write=1,2 -s 1024 -p PID 2>&1 | grep "^ |" | cut -c11-60 | sed -e 's/ //g' | xxd -r -p

    # https://www.commandlinefu.com/commands/view/6743/intercept-stdoutstderr-of-another-process-or-disowned-process
    $ strace -e write=1,2 -p $PID 2>&1 | sed -un "/^ |/p" | sed -ue "s/^.\{9\}\(.\{50\}\).\+/\1/g" -e 's/ //g' | xxd -r -p
    ```
*   [debug script](https://askubuntu.com/a/678919/92979)

    ```bash
    $ strace -e clone,execve,pipe,dup2 \
             -f bash -c 'cat <(/bin/true) <(/bin/false) <(/bin/echo)'
    execve("/usr/bin/bash", ["bash", "-c", "cat <(/bin/true) <(/bin/false) <"...], 0x7fff9b9c6f98 /* 75 vars */) = 0
    pipe([3, 4])                            = 0
    dup2(3, 63)                             = 63
    clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f7cf6a8ca10) = 289963
    strace: Process 289963 attached
    [pid 289962] pipe([3, 4])               = 0
    [pid 289962] dup2(3, 62)                = 62
    [pid 289962] clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD <unfinished ...>
    [pid 289963] dup2(4, 1)                 = 1
    [pid 289962] <... clone resumed>, child_tidptr=0x7f7cf6a8ca10) = 289964
    strace: Process 289964 attached
    [pid 289963] clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD <unfinished ...>
    [pid 289962] pipe([3, 4])               = 0
    strace: Process 289965 attached
    [pid 289963] <... clone resumed>, child_tidptr=0x7f7cf6a8ca10) = 289965
    [pid 289962] dup2(3, 61)                = 61
    [pid 289962] clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD <unfinished ...>
    [pid 289964] dup2(4, 1)                 = 1
    [pid 289965] execve("/bin/true", ["/bin/true"], 0x55ec7c007680 /* 73 vars */strace: Process 289966 attached
     <unfinished ...>
    [pid 289962] <... clone resumed>, child_tidptr=0x7f7cf6a8ca10) = 289966
    [pid 289964] clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD <unfinished ...>
    [pid 289965] <... execve resumed>)      = 0
    strace: Process 289967 attached
    [pid 289964] <... clone resumed>, child_tidptr=0x7f7cf6a8ca10) = 289967
    [pid 289966] dup2(4, 1)                 = 1
    [pid 289967] execve("/bin/false", ["/bin/false"], 0x55ec7c007af0 /* 73 vars */ <unfinished ...>
    [pid 289966] clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f7cf6a8ca10) = 289968
    [pid 289967] <... execve resumed>)      = 0
    strace: Process 289968 attached
    [pid 289962] execve("/usr/bin/cat", ["cat", "/dev/fd/63", "/dev/fd/62", "/dev/fd/61"], 0x55ec7c007bc0 /* 73 vars */ <unfinished ...>
    [pid 289968] execve("/bin/echo", ["/bin/echo"], 0x55ec7c007e20 /* 73 vars */ <unfinished ...>
    [pid 289962] <... execve resumed>)      = 0
    [pid 289968] <... execve resumed>)      = 0
    [pid 289965] +++ exited with 0 +++
    [pid 289963] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=289965, si_uid=10564, si_status=0, si_utime=0, si_stime=0} ---
    [pid 289963] +++ exited with 0 +++
    [pid 289962] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=289963, si_uid=10564, si_status=0, si_utime=0, si_stime=0} ---
    [pid 289967] +++ exited with 1 +++
    [pid 289964] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=289967, si_uid=10564, si_status=1, si_utime=0, si_stime=0} ---
    [pid 289964] +++ exited with 1 +++
    [pid 289962] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=289964, si_uid=10564, si_status=1, si_utime=0, si_stime=0} ---

    [pid 289968] +++ exited with 0 +++
    [pid 289966] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=289968, si_uid=10564, si_status=0, si_utime=0, si_stime=0} ---
    [pid 289966] +++ exited with 0 +++
    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=289966, si_uid=10564, si_status=0, si_utime=0, si_stime=0} ---
    +++ exited with 0 +++
    ```
*   [xtrace](https://unix.stackexchange.com/a/441389/29178)

    ```bash
    xtrace() {
      local eval_cmd
      printf -v eval_cmd '%q' "${@}"
      { set -x
        eval "${eval_cmd}"
      } 2>&1 | grep '^++'
      return "${PIPESTATUS[0]}"
    }
    ```

### [`dtruss`](https://stackoverflow.com/a/31045613/2940319)

> \[!TIP|label:references:]
>
> * the MacOS alternatives `strace`
> * [Using modified dtruss.sh](https://stackoverflow.com/q/73724074/2940319)

```bash
$ sudo dtruss <cmd>
```

```bash
$ sudo dtruss ls
dtrace: system integrity protection is on, some features will not be available

SYSCALL(args)      = return
README.md   artifactory  devops   jenkins  osx    screenshot  vim
SUMMARY.md  cheatsheet   english  linux    programming  tools     virtualization
munmap(0x1155AB000, 0xA0000)     = 0 0
munmap(0x11564B000, 0x8000)    = 0 0
munmap(0x115653000, 0x4000)    = 0 0
munmap(0x115657000, 0x4000)    = 0 0
munmap(0x11565B000, 0x58000)     = 0 0
fsgetpath(0x7FF7BA418580, 0x400, 0x7FF7BA418568)     = 40 0
fsgetpath(0x7FF7BA418580, 0x400, 0x7FF7BA418568)     = 14 0
csrctl(0x0, 0x7FF7BA41898C, 0x4)     = -1 1
__mac_syscall(0x7FF819AD4E1B, 0x2, 0x7FF7BA4187F0)     = 0 0
csrctl(0x0, 0x7FF7BA41899C, 0x4)     = -1 1
__mac_syscall(0x7FF819AD1DA4, 0x5A, 0x7FF7BA418930)    = 0 0
dtrace: error on enabled probe ID 1741 (ID 573: syscall::sysctl:return): invalid kernel access in action #10 at DIF offset 28
dtrace: error on enabled probe ID 1741 (ID 573: syscall::sysctl:return): invalid kernel access in action #10 at DIF offset 28
dtrace: error on enabled probe ID 1741 (ID 573: syscall::sysctl:return): invalid kernel access in action #10 at DIF offset 28
dtrace: error on enabled probe ID 1741 (ID 573: syscall::sysctl:return): invalid kernel access in action #10 at DIF offset 28
open("/\0", 0x20100000, 0x0)     = 3 0
openat(0x3, "System/Cryptexes/OS\0", 0x100000, 0x0)    = 4 0
dup(0x4, 0x0, 0x0)     = 5 0
fstatat64(0x4, 0x7FF7BA4176D1, 0x7FF7BA417AD0)     = 0 0
openat(0x4, "System/Library/dyld/\0", 0x100000, 0x0)     = 6 0
fcntl(0x6, 0x32, 0x7FF7BA417760)     = 0 0
dup(0x6, 0x0, 0x0)     = 7 0
dup(0x5, 0x0, 0x0)     = 8 0
close(0x3)     = 0 0
close(0x5)     = 0 0
close(0x4)     = 0 0
close(0x6)     = 0 0
shared_region_check_np(0x7FF7BA418048, 0x0, 0x0)     = 0 0
fsgetpath(0x7FF7BA4185B0, 0x400, 0x7FF7BA4184E8)     = 83 0
fcntl(0x8, 0x32, 0x7FF7BA4185B0)     = 0 0
close(0x8)     = 0 0
close(0x7)     = 0 0
getfsstat64(0x0, 0x0, 0x2)     = 9 0
getfsstat64(0x106102040, 0x4C38, 0x2)    = 9 0
getattrlist("/\0", 0x7FF7BA4184F0, 0x7FF7BA418460)     = 0 0
stat64("/System/Volumes/Preboot/Cryptexes/OS/System/Library/dyld/dyld_shared_cache_x86_64h\0", 0x7FF7BA418828, 0x0)    = 0 0
dtrace: error on enabled probe ID 1690 (ID 845: syscall::stat64:return): invalid address (0x0) in action #11 at DIF offset 12
stat64("/usr/local/Cellar/coreutils/9.4/bin/gls\0", 0x7FF7BA417CC0, 0x0)     = 0 0
open("/usr/local/Cellar/coreutils/9.4/bin/gls\0", 0x0, 0x0)    = 3 0
mmap(0x0, 0x33358, 0x1, 0x40002, 0x3, 0x0)     = 0x105B18000 0
fcntl(0x3, 0x32, 0x7FF7BA417DD0)     = 0 0
close(0x3)     = 0 0
munmap(0x105B18000, 0x33358)     = 0 0
stat64("/usr/local/Cellar/coreutils/9.4/bin/gls\0", 0x7FF7BA418220, 0x0)     = 0 0
stat64("/usr/lib/libSystem.B.dylib\0", 0x7FF7BA417230, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/libSystem.B.dylib\0", 0x7FF7BA4171E0, 0x0)    = -1 2
stat64("/usr/lib/libSystem.B.dylib\0", 0x7FF7BA417230, 0x0)    = -1 2
stat64("/usr/lib/libobjc.A.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/libobjc.A.dylib\0", 0x7FF7BA414E30, 0x0)    = -1 2
stat64("/usr/lib/libobjc.A.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_blocks.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_blocks.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_blocks.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libxpc.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libxpc.dylib\0", 0x7FF7BA414E30, 0x0)  = -1 2
stat64("/usr/lib/system/libxpc.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_trace.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_trace.dylib\0", 0x7FF7BA414E20, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_trace.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libcorecrypto.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libcorecrypto.dylib\0", 0x7FF7BA414E30, 0x0) = -1 2
stat64("/usr/lib/system/libcorecrypto.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_malloc.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_malloc.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_malloc.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libdispatch.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libdispatch.dylib\0", 0x7FF7BA414E30, 0x0)   = -1 2
stat64("/usr/lib/system/libdispatch.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_featureflags.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_featureflags.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_featureflags.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_c.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_c.dylib\0", 0x7FF7BA414E30, 0x0)   = -1 2
stat64("/usr/lib/system/libsystem_c.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/libc++.1.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/libc++.1.dylib\0", 0x7FF7BA414E30, 0x0)     = -1 2
stat64("/usr/lib/libc++.1.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/libc++abi.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/libc++abi.dylib\0", 0x7FF7BA414E30, 0x0)    = -1 2
stat64("/usr/lib/libc++abi.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libdyld.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libdyld.dylib\0", 0x7FF7BA414E30, 0x0)   = -1 2
stat64("/usr/lib/system/libdyld.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_info.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_info.dylib\0", 0x7FF7BA414E30, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_info.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_darwin.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_darwin.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_darwin.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_notify.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_notify.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_notify.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_networkextension.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_networkextension.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_networkextension.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_asl.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_asl.dylib\0", 0x7FF7BA414E30, 0x0) = -1 2
stat64("/usr/lib/system/libsystem_asl.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_symptoms.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_symptoms.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_symptoms.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_containermanager.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_containermanager.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_containermanager.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_configuration.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_configuration.dylib\0", 0x7FF7BA414E20, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_configuration.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_sandbox.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_sandbox.dylib\0", 0x7FF7BA414E20, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_sandbox.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libquarantine.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libquarantine.dylib\0", 0x7FF7BA414E30, 0x0) = -1 2
stat64("/usr/lib/system/libquarantine.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_coreservices.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_coreservices.dylib\0", 0x7FF7BA414E20, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_coreservices.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_m.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_m.dylib\0", 0x7FF7BA414E30, 0x0)   = -1 2
stat64("/usr/lib/system/libsystem_m.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libmacho.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libmacho.dylib\0", 0x7FF7BA414E30, 0x0)  = -1 2
stat64("/usr/lib/system/libmacho.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libcommonCrypto.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libcommonCrypto.dylib\0", 0x7FF7BA414E20, 0x0)     = -1 2
stat64("/usr/lib/system/libcommonCrypto.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libunwind.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libunwind.dylib\0", 0x7FF7BA414E30, 0x0)   = -1 2
stat64("/usr/lib/system/libunwind.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/liboah.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/liboah.dylib\0", 0x7FF7BA414E30, 0x0)     = -1 2
stat64("/usr/lib/liboah.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libcopyfile.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libcopyfile.dylib\0", 0x7FF7BA414E30, 0x0)   = -1 2
stat64("/usr/lib/system/libcopyfile.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libcompiler_rt.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libcompiler_rt.dylib\0", 0x7FF7BA414E30, 0x0)    = -1 2
stat64("/usr/lib/system/libcompiler_rt.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_collections.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_collections.dylib\0", 0x7FF7BA414E20, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_collections.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_secinit.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_secinit.dylib\0", 0x7FF7BA414E20, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_secinit.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libremovefile.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libremovefile.dylib\0", 0x7FF7BA414E30, 0x0) = -1 2
stat64("/usr/lib/system/libremovefile.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libkeymgr.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libkeymgr.dylib\0", 0x7FF7BA414E30, 0x0)   = -1 2
stat64("/usr/lib/system/libkeymgr.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_dnssd.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_dnssd.dylib\0", 0x7FF7BA414E20, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_dnssd.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/usr/lib/system/libcache.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libcache.dylib\0", 0x7FF7BA414E30, 0x0)  = -1 2
stat64("/usr/lib/system/libcache.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/libSystem.B.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/libSystem.B.dylib\0", 0x7FF7BA414E30, 0x0)    = -1 2
stat64("/usr/lib/libSystem.B.dylib\0", 0x7FF7BA414E80, 0x0)    = -1 2
stat64("/usr/lib/system/libsystem_darwindirectory.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
stat64("/System/Volumes/Preboot/Cryptexes/OS/usr/lib/system/libsystem_darwindirectory.dylib\0", 0x7FF7BA414E20, 0x0)     = -1 2
stat64("/usr/lib/system/libsystem_darwindirectory.dylib\0", 0x7FF7BA414E80, 0x0)     = -1 2
open("/dev/dtracehelper\0", 0x2, 0x0)    = 3 0
ioctl(0x3, 0x80086804, 0x7FF7BA416E18)     = 0 0
close(0x3)     = 0 0
open("/usr/local/Cellar/coreutils/9.4/bin/gls\0", 0x0, 0x0)    = 3 0
__mac_syscall(0x7FF819AD4E1B, 0x2, 0x7FF7BA4163D0)     = 0 0
map_with_linking_np(0x7FF7BA415FB0, 0x1, 0x7FF7BA415FE0)     = -1 22
close(0x3)     = 0 0
mprotect(0x105B08000, 0x4000, 0x1)     = 0 0
shared_region_check_np(0xFFFFFFFFFFFFFFFF, 0x0, 0x0)     = 0 0
mprotect(0x106100000, 0x40000, 0x1)    = 0 0
access("/AppleInternal/XBS/.isChrooted\0", 0x0, 0x0)     = -1 2
bsdthread_register(0x7FF819DC9B9C, 0x7FF819DC9B88, 0x2000)     = 1073742303 0
getpid(0x0, 0x0, 0x0)    = 49682 0
shm_open(0x7FF819C6CF42, 0x0, 0x19C6B388)    = 3 0
fstat64(0x3, 0x7FF7BA417340, 0x0)    = 0 0
mmap(0x0, 0x4000, 0x1, 0x40001, 0x3, 0x0)    = 0x105B1A000 0
close(0x3)     = 0 0
ioctl(0x2, 0x4004667A, 0x7FF7BA417404)     = 0 0
mprotect(0x105B23000, 0x1000, 0x0)     = 0 0
mprotect(0x105B2D000, 0x1000, 0x0)     = 0 0
mprotect(0x105B2E000, 0x1000, 0x0)     = 0 0
mprotect(0x105B38000, 0x1000, 0x0)     = 0 0
mprotect(0x105B1E000, 0x98, 0x1)     = 0 0
mprotect(0x105B1E000, 0x98, 0x3)     = 0 0
mprotect(0x105B1E000, 0x98, 0x1)     = 0 0
mprotect(0x105B39000, 0x1000, 0x1)     = 0 0
mprotect(0x105B3A000, 0x98, 0x1)     = 0 0
mprotect(0x105B3A000, 0x98, 0x3)     = 0 0
mprotect(0x105B3A000, 0x98, 0x1)     = 0 0
mprotect(0x105B1E000, 0x98, 0x3)     = 0 0
mprotect(0x105B1E000, 0x98, 0x1)     = 0 0
mprotect(0x105B39000, 0x1000, 0x3)     = 0 0
mprotect(0x105B39000, 0x1000, 0x1)     = 0 0
mprotect(0x106100000, 0x40000, 0x3)    = 0 0
mprotect(0x106100000, 0x40000, 0x1)    = 0 0
issetugid(0x0, 0x0, 0x0)     = 0 0
mprotect(0x106100000, 0x40000, 0x3)    = 0 0
getentropy(0x7FF7BA416C30, 0x20, 0x0)    = 0 0
mprotect(0x106100000, 0x40000, 0x1)    = 0 0
mprotect(0x106100000, 0x40000, 0x3)    = 0 0
mprotect(0x106100000, 0x40000, 0x1)    = 0 0
getattrlist("/usr/local/opt/coreutils/libexec/gnubin/ls\0", 0x7FF7BA4172E0, 0x7FF7BA4172F8)    = 0 0
access("/usr/local/Cellar/coreutils/9.4/bin\0", 0x4, 0x0)    = 0 0
open("/usr/local/Cellar/coreutils/9.4/bin\0", 0x0, 0x0)    = 3 0
fstat64(0x3, 0x7FAEECF042E0, 0x0)    = 0 0
csrctl(0x0, 0x7FF7BA41753C, 0x4)     = 0 0
fcntl(0x3, 0x32, 0x7FF7BA4171F0)     = 0 0
close(0x3)     = 0 0
open("/usr/local/Cellar/coreutils/9.4/bin/Info.plist\0", 0x0, 0x0)     = -1 2
proc_info(0x2, 0xC212, 0xD)    = 64 0
csops_audittoken(0xC212, 0x10, 0x7FF7BA417540)     = -1 22
dtrace: error on enabled probe ID 1741 (ID 573: syscall::sysctl:return): invalid kernel access in action #10 at DIF offset 28
dtrace: error on enabled probe ID 1741 (ID 573: syscall::sysctl:return): invalid kernel access in action #10 at DIF offset 28
csops(0xC212, 0x0, 0x7FF7BA4179A4)     = 0 0
mprotect(0x106100000, 0x40000, 0x3)    = 0 0
open_nocancel("/usr/share/locale/en_US.UTF-8/LC_COLLATE\0", 0x0, 0x0)    = 3 0
fcntl_nocancel(0x3, 0x3, 0x0)    = 0 0
getrlimit(0x1008, 0x7FF7BA417D10, 0x0)     = 0 0
fstat64(0x3, 0x7FF7BA417C88, 0x0)    = 0 0
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
close_nocancel(0x3)    = 0 0
open_nocancel("/usr/share/locale/en_US.UTF-8/LC_CTYPE\0", 0x0, 0x0)    = 3 0
fcntl_nocancel(0x3, 0x3, 0x0)    = 0 0
fstat64(0x3, 0x7FF7BA417DD0, 0x0)    = 0 0
fstat64(0x3, 0x7FF7BA417BD8, 0x0)    = 0 0
lseek(0x3, 0x0, 0x1)     = 0 0
lseek(0x3, 0x0, 0x0)     = 0 0
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
close_nocancel(0x3)    = 0 0
open_nocancel("/usr/share/locale/en_US.UTF-8/LC_MONETARY\0", 0x0, 0x0)     = 3 0
fstat64(0x3, 0x7FF7BA417DD8, 0x0)    = 0 0
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
close_nocancel(0x3)    = 0 0
open_nocancel("/usr/share/locale/en_US.UTF-8/LC_NUMERIC\0", 0x0, 0x0)    = 3 0
fstat64(0x3, 0x7FF7BA417DD8, 0x0)    = 0 0
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
close_nocancel(0x3)    = 0 0
open_nocancel("/usr/share/locale/en_US.UTF-8/LC_TIME\0", 0x0, 0x0)     = 3 0
fstat64(0x3, 0x7FF7BA417DD8, 0x0)    = 0 0
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
close_nocancel(0x3)    = 0 0
open_nocancel("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/LC_MESSAGES\0", 0x0, 0x0)     = 3 0
fstat64(0x3, 0x7FF7BA417DD8, 0x0)    = 0 0
dtrace: error on enabled probe ID 1714 (ID 961: syscall::read_nocancel:return): invalid kernel access in action #12 at DIF offset 68
close_nocancel(0x3)    = 0 0
ioctl(0x1, 0x4004667A, 0x7FF7BA418324)     = 0 0
ioctl(0x1, 0x40087468, 0x7FF7BA4183F0)     = 0 0
open_nocancel(".\0", 0x1100004, 0x0)     = 3 0
dtrace: error on enabled probe ID 1741 (ID 573: syscall::sysctl:return): invalid kernel access in action #10 at DIF offset 28
dtrace: error on enabled probe ID 1741 (ID 573: syscall::sysctl:return): invalid kernel access in action #10 at DIF offset 28
fstatfs64(0x3, 0x7FF7BA417AB0, 0x0)    = 0 0
getdirentries64(0x3, 0x7FAEED80FC00, 0x2000)     = 568 0
close_nocancel(0x3)    = 0 0
sigprocmask(0x1, 0x0, 0x7FF7BA418350)    = 0x0 0
sigaltstack(0x0, 0x7FF7BA418340, 0x0)    = 0 0
fstat64(0x1, 0x7FF7BA416E58, 0x0)    = 0 0
ioctl(0x1, 0x4004667A, 0x7FF7BA416EA4)     = 0 0
dtrace: error on enabled probe ID 1712 (ID 963: syscall::write_nocancel:return): invalid kernel access in action #12 at DIF offset 68
dtrace: error on enabled probe ID 1712 (ID 963: syscall::write_nocancel:return): invalid kernel access in action #12 at DIF offset 68
close_nocancel(0x1)    = 0 0
close_nocancel(0x2)    = 0 0
```

* troubleshooting
  *   [`dtrace: system integrity protection is on`](https://stackoverflow.com/a/60910410/2940319)

      > \[!TIP]
      >
      > * [\* iMarlso: osx/system integrity protection](https://github.com/marslo/ibook/blob/marslo/docs/osx/osx.html#system-integrity-protection)

      ```
      # csrutil disable
      # or
      # csrutil enable --without dtrace
      # or
      # csrutil enable --without dtrace --without debug
      ```

### sar

### netcat

> \[!NOTE|label:references:]
>
> * [the netcat command in linux](https://www.baeldung.com/linux/netcat-command)

*   check particular port

    ```bash
    $ nc -zv 127.0.0.1 22
    Connection to 127.0.0.1 port 22 [tcp/ssh] succeeded!
    ```
*   check ports in range

    ```bash
    $ nc -znv -w 1 127.0.0.1 20-30
    nc: connectx to 127.0.0.1 port 20 (tcp) failed: Connection refused
    nc: connectx to 127.0.0.1 port 21 (tcp) failed: Connection refused
    Connection to 127.0.0.1 port 22 [tcp/*] succeeded!
    nc: connectx to 127.0.0.1 port 23 (tcp) failed: Connection refused
    nc: connectx to 127.0.0.1 port 24 (tcp) failed: Connection refused
    nc: connectx to 127.0.0.1 port 25 (tcp) failed: Connection refused
    nc: connectx to 127.0.0.1 port 26 (tcp) failed: Connection refused
    nc: connectx to 127.0.0.1 port 27 (tcp) failed: Connection refused
    nc: connectx to 127.0.0.1 port 28 (tcp) failed: Connection refused
    ```
*   running simple web server

    ```bash
    $ cat > index.html <<<EOF
    <!DOCTYPE html>
    <html>
        <head>
            <title>Simple Netcat Server</title>
        </head>
        <body>
            <h1>Welcome to simple netcat server!<h1>
        </body>
        </body>
    <html>
    EOF

    $ echo -e "HTTP/1.1 200 OK\n\n$(cat index.html)" | nc -l 1234
    ```
*   or getting more

    ```bash
    $ while true; do echo -e "HTTP/1.1 200 OK\n\n$(cat index.html)" | nc -l -w 1 1234; done
    GET / HTTP/1.1
    Host: localhost:1234
    Connection: keep-alive
    sec-ch-ua: "Chromium";v="110", "Not A(Brand";v="24", "Google Chrome";v="110"
    sec-ch-ua-mobile: ?0
    sec-ch-ua-platform: "macOS"
    Upgrade-Insecure-Requests: 1
    User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36
    Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
    Sec-Fetch-Site: none
    Sec-Fetch-Mode: navigate
    Sec-Fetch-User: ?1
    Sec-Fetch-Dest: document
    Accept-Encoding: gzip, deflate, br
    Accept-Language: en,zh-CN;q=0.9,zh;q=0.8,en-US;q=0.7

    GET /favicon.ico HTTP/1.1
    Host: localhost:1234
    Connection: keep-alive
    sec-ch-ua: "Chromium";v="110", "Not A(Brand";v="24", "Google Chrome";v="110"
    sec-ch-ua-mobile: ?0
    User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36
    sec-ch-ua-platform: "macOS"
    Accept: image/avif,image/webp,image/apng,image/svg+xml,image/*,*/*;q=0.8
    Sec-Fetch-Site: same-origin
    Sec-Fetch-Mode: no-cors
    Sec-Fetch-Dest: image
    Referer: http://localhost:1234/
    Accept-Encoding: gzip, deflate, br
    Accept-Language: en,zh-CN;q=0.9,zh;q=0.8,en-US;q=0.7
    ...
    ```

    ![netcat web service](https://1999659500-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MHqOSW6on5cHbtwcSH6%2Fuploads%2Fgit-blob-217529149b5275c3c848c357d16760b891251c9e%2Fnetcat-1234-html.png?alt=media)
* [reverse proxy with netcat](https://www.baeldung.com/linux/netcat-command#reverse-proxy-with-netcat)
*   [emulating netcat -e](https://www.commandlinefu.com/commands/view/11061/emulating-netcat-e-netcat-traditional-or-netcat-openbsd-with-the-gnu-netcat)

    ```bash
    $ mkfifo foo ; nc -lk 2600 0<foo | /bin/bash 1>foo
    ```

### `ip`

```bash
$ ip addr show | sed -nE "s/inet\s(.*)\/[0-9]+.*\s(\w+)/\2 \1/p"
  lo0 127.0.0.1
  en0 192.168.1.71

# for linux
$ ip addr show | sed -nE "s/inet\s(.*)\/[0-9]+.*\s(\w+)/\2 \1/p" | column -to ' => '
lo0 => 127.0.0.1
en0 => 192.168.1.71
```

### [datadog](https://www.datadoghq.com/)

## others

> \[!NOTE|label:references:]
>
> * [完全指南：在 Linux 中如何打印和管理打印机](https://linux.cn/article-9538-1.html)
> * [440+ 个免费的编程 & 计算机科学的在线课程](https://linux.cn/article-9443-1.html)
> * [在 Linux 上用 DNS 实现简单的负载均衡](https://linux.cn/article-9777-1.html)
> * [Python 字节码介绍](https://linux.cn/article-9816-1.html)
