There are many ways to install software in Linux systems, so there is no universal method to check whether a certain software has been installed. However, I have summarized some types below for your reference:
1. If the rpm package is installed, you can use rpm -qa to see it. If you want to find out whether a certain software package is installed, use rpm -qa | grep "the name of the software or package".
rpm -qa | grep ruby
2. If installed with deb package, you can use dpkg -l to see it. If you are looking for a specific software package, use dpkg -l | grep "the name of the software or package";
dpkg -l | grep ruby
3. If installed using the yum method, you can use yum list installed to search. If you are looking for a specified package, add | grep "software name or package name" after the command;
yum list installed | grep ruby
4. If you compile and install the source code package yourself, such as .tar.gz or tar.bz2, you can only check whether the executable file exists.
Neither of the above two methods can see the package installed in this source code form. If installed as the root user, the executable programs are usually in the /sbin:/usr/bin directory.
There are other methods, please indicate.
The following are the additions from other netizens
1. If the rpm package is installed, you can use rpm -qa to see it. If you want to find out whether a certain software package is installed, use rpm -qa | grep "the name of the software or package"
2. Installed with deb package, you can use dpkg -l to see it. If you are looking for a specific software package, use dpkg -l | grep "the name of the software or package"
3. If installed using the yum method, you can use yum list installed to search. If you are looking for a specified package, use yum list installed | grep "software name or package name"
The above is the detailed content of Check if Linux has a specific package installed. For more information, please follow other related articles on the PHP Chinese website!

The security models of Linux and Windows each have their own advantages. Linux provides flexibility and customizability, enabling security through user permissions, file system permissions, and SELinux/AppArmor. Windows focuses on user-friendliness and relies on WindowsDefender, UAC, firewall and BitLocker to ensure security.

Linux and Windows differ in hardware compatibility: Windows has extensive driver support, and Linux depends on the community and vendors. To solve Linux compatibility problems, you can manually compile drivers, such as cloning RTL8188EU driver repository, compiling and installing; Windows users need to manage drivers to optimize performance.

The main differences between Linux and Windows in virtualization support are: 1) Linux provides KVM and Xen, with outstanding performance and flexibility, suitable for high customization environments; 2) Windows supports virtualization through Hyper-V, with a friendly interface, and is closely integrated with the Microsoft ecosystem, suitable for enterprises that rely on Microsoft software.

The main tasks of Linux system administrators include system monitoring and performance tuning, user management, software package management, security management and backup, troubleshooting and resolution, performance optimization and best practices. 1. Use top, htop and other tools to monitor system performance and tune it. 2. Manage user accounts and permissions through useradd commands and other commands. 3. Use apt and yum to manage software packages to ensure system updates and security. 4. Configure a firewall, monitor logs, and perform data backup to ensure system security. 5. Troubleshoot and resolve through log analysis and tool use. 6. Optimize kernel parameters and application configuration, and follow best practices to improve system performance and stability.

Learning Linux is not difficult. 1.Linux is an open source operating system based on Unix and is widely used in servers, embedded systems and personal computers. 2. Understanding file system and permission management is the key. The file system is hierarchical, and permissions include reading, writing and execution. 3. Package management systems such as apt and dnf make software management convenient. 4. Process management is implemented through ps and top commands. 5. Start learning from basic commands such as mkdir, cd, touch and nano, and then try advanced usage such as shell scripts and text processing. 6. Common errors such as permission problems can be solved through sudo and chmod. 7. Performance optimization suggestions include using htop to monitor resources, cleaning unnecessary files, and using sy

The average annual salary of Linux administrators is $75,000 to $95,000 in the United States and €40,000 to €60,000 in Europe. To increase salary, you can: 1. Continuously learn new technologies, such as cloud computing and container technology; 2. Accumulate project experience and establish Portfolio; 3. Establish a professional network and expand your network.

The main uses of Linux include: 1. Server operating system, 2. Embedded system, 3. Desktop operating system, 4. Development and testing environment. Linux excels in these areas, providing stability, security and efficient development tools.

The Internet does not rely on a single operating system, but Linux plays an important role in it. Linux is widely used in servers and network devices and is popular for its stability, security and scalability.


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