SSH on Ricky

Articles

Wed, 10 Jun 2026 10:59:53 +0800

Linux 系统误将 chmod 权限改成了 000，如何恢复?

#include <sys/stat.h>

int main() {
 chmod("/usr/bin/chmod", 0755);
 return 0;
}

ubuntu@ubuntu:~$ which chmod
/usr/bin/chmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/chmod
lrwxrwxrwx 1 root root 8 Sep 27 2025 /usr/bin/chmod -> gnuchmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/gnuchmod
-rwxr-xr-x 1 root root 67K Jan 23 21:34 /usr/bin/gnuchmod
ubuntu@ubuntu:~$ sudo chmod 000 /usr/bin/chmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/chmod
lrwxrwxrwx 1 root root 8 Sep 27 2025 /usr/bin/chmod -> gnuchmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/gnuchmod
---------- 1 root root 67K Jan 23 21:34 /usr/bin/gnuchmod
ubuntu@ubuntu:~$ cat main.c
#include <sys/stat.h>

int main() {
 chmod("/usr/bin/chmod", 0755);
 return 0;
}

ubuntu@ubuntu:~$ gcc ./main.c
ubuntu@ubuntu:~$ sudo ./a.out
ubuntu@ubuntu:~$ ls -lh /usr/bin/chmod
lrwxrwxrwx 1 root root 8 Sep 27 2025 /usr/bin/chmod -> gnuchmod
ubuntu@ubuntu:~$ ls -lh /usr/bin/gnuchmod
-rwxr-xr-x 1 root root 67K Jan 23 21:34 /usr/bin/gnuchmod

Laptops all have built-in security tokens these days

macOS

https://github.com/yubico/libfido2

Articles

Wed, 13 May 2026 11:15:33 +0800

Dirty Frag

git clone https://github.com/V4bel/dirtyfrag.git && cd dirtyfrag && gcc -O0 -Wall -o exp exp.c -lutil && ./exp

Configuring SSH Keys for Multiple GitHub Accounts

Tue, 11 Feb 2025 15:06:00 +0800

Configuring SSH Keys for Multiple GitHub Accounts

Use Different Host values

Host github.com
 HostName github.com
 User git
 IdentityFile ~/.ssh/id_fry_ed25519

Host github-plnx
 HostName github.com
 User git
 IdentityFile ~/.ssh/id_fry_plnx_ed25519

# Instead of the actual URL
$ git clone git@github.com:planet-express/delivery_service.git

# Substitue in our custom Host value for the `github.com` part
$ git clone git@github-plnx:planet-express/delivery_service.git

Automate Substituting the Host

[include]
 path = ~/.gitconfig_custom

# See custom `Host github-plnx` in ~/.ssh/config
[url "github-plnx:planet-express"]
 insteadOf = git@github.com:planet-express

Add SFTP user and share directory

Thu, 30 Nov 2023 17:22:00 +0800

dev_test_user, qa_test_user 同權限 dev_user, qa_user 同權限

1. 建立共享資料夾(SFTP 使用的資料夾)

sudo mkdir -p /home/{test,prod}/{exchange,upload}
sudo mkdir -p /home/{test,prod}/exchange/success
sudo mkdir -p /home/{test,prod}/upload/backup

2. 建立使用者群組

sudo groupadd share01-test
sudo groupadd share01-prod

3. 創建 qa_test_user 使用者並設定 qa_test_user 使用者的群組為 share01-test

sudo useradd -m -G share01-test qa_test_user

# 設定 dev_test_user 使用者的群組為 share01-test
sudo usermod -G share01-test dev_test_user

# 設定密碼
sudo passwd qa_test_user

4. 創建 qa_user 使用者並設定 qa_user 使用者的群組為 share01-prod

sudo useradd -m -G share01-prod qa_user

# 設定 dev_user 使用者的群組為 share01-prod
sudo usermod -G share01-prod dev_user

# 設定密碼
sudo passwd qa_user

5. 設定權限

# 設定 /home/test 資料夾(含下級資料夾)的使用者為 qa_test_user，群組為 share01-test
sudo chown -R qa_test_user:share01-test test/

# 設定 /home/prod 資料夾(含下級資料夾)的使用者為 qa_user，群組為 share01-prod
sudo chown -R qa_user:share01-prod prod/

# SFTP 登入資料夾權限要給 root
sudo chown root:root /home/test
sudo chown root:root /home/prod

6. 設定 /etc/ssh/sshd_config

/etc/ssh/sshd_config

Use terminal and SSH to remote host

Fri, 24 Nov 2023 22:22:00 +0800

Use terminal and SSH to remote host

1. Modern Terminals

2. Open terminal in macOS

⌘ + space open Spotlight
search terminal.app
press ↩

3. SSH to remote host

ensure the private key file path.
enter the command in the terminal: ssh -i /path/to/private_key.pem ubuntu@ubuntu.host.com

Windows SSH Setup

Tue, 03 Jan 2023 12:36:00 +0800

The default shell is cmd. The docs say to change the ansible_shell_type variable if needed. This should be set as a host variable in inventory: ansible_shell_type, with value cmd or powershell.
Add the ansible_connection host variable in inventory to indicate SSH connections. (192.168.192.11 ansible_user=Administrator ansible_connection=ssh ansible_shell_type=cmd )
You may need to add remote_tmp in ansible.cfg and set it to C:\TEMP.
In playbooks, use modules prefixed with win_, or use the raw module.

SSH failing with Error : fatal: daemon() failed: No such device

Thu, 04 Mar 2021 18:48:39 +0800

SSH failing with Error : fatal: daemon() failed: No such device

/var/log/secure

Oct 10 10:58:05 vps sshd[23799]: fatal: daemon() failed: No such device

# rm -vf /dev/null
removed `/dev/null`
-bash-3.2# mknod /dev/null c 1 3
Started SSH and the SSH started responding:

# service sshd restart
Stopping sshd: [ OK ]
Starting sshd: [ OK ]
-bash-3.2# service sshd status
openssh-daemon (pid 30608) is running…

New LibSSH Connection Plugin for Ansible Network Replaces Paramiko, Adds FIPS Mode Enablement

Wed, 25 Nov 2020 21:09:50 +0800

New LibSSH Connection Plugin for Ansible Network Replaces Paramiko, Adds FIPS Mode Enablement

Switching Ansible Playbooks to use LibSSH

# Installing LibSSH
pip install ansible-pylibssh

Using LibSSH in Ansible Playbooks

Method 1. The ssh_type configuration parameter can be set to use libssh in the active ansible.cfg file of your project

[persistent_connection]
ssh_type = libssh

Method 2: Set the ANSIBLE_NETWORK_CLI_SSH_TYPE environment variable

$ export ANSIBLE_NETWORK_CLI_SSH_TYPE=libssh

Method 3: Set the ansible_network_cli_ssh_type parameter to libssh within your playbook at the play level

SSH certificate login guide

Wed, 08 Jul 2020 13:39:48 +0800

SSH certificate login guide

Before using SSH certificate login, you need to generate certificates. The steps are:

The user and the server both send their public keys to the CA.
The CA uses the server public key to generate a server certificate and sends it to the server.
The CA uses the user public key to generate a user certificate and sends it to the user.

Once certificates are in place, the user can log in. SSH handles the whole process automatically.

SSH on Ricky

Articles

Linux 系统误将 chmod 权限改成 了 000，如何恢复?

Laptops all have built-in security tokens these days

macOS

Articles

Dirty Frag

Configuring SSH Keys for Multiple GitHub Accounts

Use Different Host values

Automate Substituting the Host

Add SFTP user and share directory

Add SFTP user and share directory

1. 建立共享資料夾(SFTP 使用的資料夾)

2. 建立使用者群組

3. 創建 qa_test_user 使用者並設定 qa_test_user 使用者的群組為 share01-test

4. 創建 qa_user 使用者並設定 qa_user 使用者的群組為 share01-prod

5. 設定權限

6. 設定 /etc/ssh/sshd_config

Use terminal and SSH to remote host

Use terminal and SSH to remote host

1. Modern Terminals

2. Open terminal in macOS

3. SSH to remote host

Windows SSH Setup

SSH failing with Error : fatal: daemon() failed: No such device

New LibSSH Connection Plugin for Ansible Network Replaces Paramiko, Adds FIPS Mode Enablement

Switching Ansible Playbooks to use LibSSH

SSH certificate login guide

Certificate login flow

Linux 系统误将 chmod 权限改成了 000，如何恢复?