Two-Minute Drill

Virtual Memory Concepts

q	Virtual memory refers to using the disk space as if it were the physical memory of the computer, and this disk space is called swap space. Files in the swap space are managed by the TMPFS file system.
q	Virtual swap space refers to the addresses that are in the physical memory and act as the addresses of the swap space and are called virtual swap space addresses, or just virtual addresses. They are used to avoid the problem of having to configure a large disk space as swap space.
q	Virtual swap space is controlled by the SWAPFS file system, which provides virtual swap space addresses as opposed to physical swap space addresses in response to the requests for reserving swap space. SWAPFS also maps the virtual addresses to physical swap space addresses when the paging starts.

Managing Swap Space

q	You use the mkfile command to create a swap file.
q	You can use the swap command to manage the swap space: the -l and -s options display information about the swap space, the -a option activates the swap file, and the -d option makes the swap space unavailable.
q	The swapadd script reads the list of swap space devices from the /etc/vfstab file and activates them by using the swap -a command each time the system is booted.

The NFS Service

q	The NFS service is started automatically when the system is mounted.
q	The /etc/dfs/dfstab file contains the share command for each file system on the server machine that needs to be shared.
q	The daemon that handles the file system requests from the clients is nfsd, and its configuration file is /etc/default/nfs.
q	The NFS service is managed by SMF; therefore, you can get its status by using the svcs command and you can start or stop the service by using the svcadm command on the SMF identifier cvc:/network/nfs/server.

Working with AutoFS

q	AutoFS is a kernel file system that supports automatic mounting and unmounting of remote file systems.
q	The autofs service is configured by the master maps file /etc/auto_master, and the direct and indirect maps files are defined in the master file.
q	The maps files basically map the mount points on the client machines to the file systems on the server machine which will be mounted to these mount points when necessary. The mount point for a direct map is fully defined in the direct maps file; the full path of a mount point in an indirect map is defined partially in the master maps file and in the indirect maps file.
q	The autofs is an SMF service under the identifier svc: /system/filesystem/autofs, and therefore can be administered with the svcadm command.

Troubleshooting NFS

q	Use the ping command to check whether the client machine can reach the server machine and vice versa.
q	Use the rpcinfo command on the client to check whether the client can access the NFS services running on the server.
q	Use the rpcinfo command remotely and locally to check whether the NFS services are running on the server.
q	Check the configuration files.

Managing Core Files and Crash Dumps

q	Core files are generated when processes running on the system terminate abnormally, whereas crash dump files are generated when the system itself crashes.
q	The coreadm command is used to manage the core files, and the dumpadm command is used to manage crash dump information. The configuration files for these two utilities are coreadm.conf and dumpadm.conf, respectively.
q	By default, a core file in the current directory of the process is created if the process terminates abnormally. When the system crashes, two files, unix. <n> and vmcore. <n>, are generated and saved, by default, in the /var/crash/<hostname> directory. Here <n> specifies the dump sequence number, and <hostname> is the name of the machine node on which the system crashed.