In which directory are system logs commonly found?

System logs are typically found in the /var/log directory. This is a standard location in Linux systems designated for log files that store various system and application messages. The /var directory is intended for files that change in size and content, including logs generated during the system's operation. Within /var/log, you will find files for different services and applications, such as syslog, dmesg, and application-specific logs.

The other choices refer to directories that are not used for storing logs in standard Linux distributions. The /usr directory primarily contains user binaries and read-only data files, while /etc is used for configuration files for the system. The /sys directory is a virtual filesystem that exposes kernel-related information and parameters; it does not store traditional log files. Therefore, the /var/log directory is the correct and conventional location for system logs in Linux.