Linux Unit iv.pdf - Unit IV System Administration Security...

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Unit IV System Administration & Security
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Contents System Administration Common Administrative Tasks Identifying administrative configuration and log files Role of System Administrator Managing user accounts Changing permissions and ownerships Creation & management of groups Checking system performance File security and permissions Becoming super user Some other tasks
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Common Administrative tasks
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P erforming backups Adding and Removing users Adding and removing hardware Restoring files from backups that users have accidentally deleted Understand the purpose of log files and how they are administered Installing new software Answering users' questions Monitoring system activity, disc use and log files Figuring out why a program has stopped working since yesterday, even though the user didn't change anything; Monitoring system security Adding new systems to the network Talking with vendors to determine if a problem is yours or theirs, and getting them to fix it when it is their problem Figuring out why "the network" ( or "the computer") is so slow Trying to free up disc space Rebooting the system after a crash Writing scripts to automate as many of the above tasks as possible
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Role of a System Administrator
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Analyzing system logs and identifying potential issues with computer systems. Introducing and integrating new technologies into existing data center environments. Performing routine audits of systems and software. Performing backups. Applying operating system updates, patches, and configuration changes. Installing and configuring new hardware and software. Adding, removing, or updating user account information, resetting passwords, etc. Answering technical queries and dealing with often frustrated users. Responsibility for security. Responsibility for documenting the configuration of the system. Troubleshooting any reported problems. System performance tuning. Ensuring that the network infrastructure is up and running.
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Password File The /etc/passwd file contains a list of users recognized by the system. The system consults this file at login time to determine a user’s UID and to verify the user’s password. Each line in the file represents one user and contains seven (7) fields separated by colons: Login name Encrypted password (unless a shadow password file is used) UID number Default GID number “Various” information, full name, phone number, etc Home directory Login shell Shadow File As computing processing power has become faster, it has become very dangerous to leave encrypted password in a world readable plain text file. For this reason, most Linux/Unix distributions hides the encrypted passwords by placing them in a separate file which is not world-readable. The file is called the shadow file and can be found in /etc/shadow.
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