Summary
Routine system administration involves a variety of tasks, many of which center around user management. Adding, deleting, and modifying user accounts and groups are critical tasks that all system administrators must master. Also related to users, you should know where to go to modify the default user environment.
System log files are critical troubleshooting tools that are maintained by the system. You should be able to configure what data is logged to what files and know how to use these log files.
Time management is important in Linux. Setting the Linux clocks (both hardware and software) and configuring NTP to keep the software clock accurate are important tasks. Tools that rely on the time include cron, anacron, and at , which enable the system to run programs in the future. These tools are used for many common system tasks, including rotating log files.
FAQ
What are the methods of creating and modifying user accounts?
Accounts can be created or modified with the help of tools designed for the purpose, such as useradd and usermod. Alternatively, you can directly edit the /etc/passwd and /etc/shadow files, which hold the account information.
What is the function of groups in Linux?
Linux groups enable security features to be applied to arbitrary groups of users. Each group holds an arbitrary collection of users, and group permissions can be set on files, giving all group members the same access rights to the files.
What is the purpose of the skeleton files?
Skeleton files provide a core set of configuration files that should be present in users’ home directories when those directories are created. They provide a starting point for users to modify their important shell and other configuration files.
How to configure system logging?
System logging is controlled via the /etc/syslog.conf file. Lines in this file describe what types of log data, generated by programs, are sent to log files and to which log files the log messages should go.
How log rotation is managed?
Log rotation is controlled via the /etc/logrotate.conf file (which typically refers to files in /etc/logrotate.d). Entries in these files tell the system whether to rotate logs at fixed intervals or when they reach particular sizes. When a log rotates, it’s renamed (and possibly compressed), a new log file is created, and the oldest archived log file may be deleted.
What are the two types of clocks in x86 and x86-64?
The hardware clock keeps time when the computer is powered down, but it isn’t used by most programs while the computer is running. Such programs refer to the software clock, which is set from the hardware clock when the computer boots.
What is the function of NTP?
The Network Time Protocol (NTP) enables a computer to set its clock based on the time maintained by an NTP server system. NTP can function as a tiered protocol, enabling one system to function as a client to an NTP server and as a server to additional NTP clients. This structure enables a single highly accurate time source to be used by anywhere from a few to (theoretically) billions of computers via a tiered system of links.
What is the difference between system and user cron jobs?
System cron jobs are controlled from /etc/crontab, are created by root , and may be run as any user (but most commonly as root ). System cron jobs are typically run at certain fixed times on an hourly, daily, weekly, or monthly basis. User cron jobs may be created by any user (various security measures permitting), are run under the authority of the account with which they’re associated, and may be run at just about any repeating interval desired.