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APing APing is the advanced ping program written in Python from scratch that can execute four type of ICMP probes :

• echo request
• address mask request
• timestamp request
• and information request

You can also change the TOS value in packets, retrieve the UTC time from a valid timestamp reply packet, or to change the TTL, even to trace the sent packets to understand better what's going on.

Acct The GNU Accounting utilities `ac', `accton', `last', `lastcomm', and `sa' add login and process accounting support to GNU/Linux. "Login accounting" provides summaries of system resource usage based on connect time, and "process accounting" provides summaries based on the commands executed on the system.

AcpiTool AcpiTool is a Linux ACPI client. It's a small command line application, intended to be a replacement for the apm tool. The primary target audience are laptop users, since these people are most interested in things like battery status, thermal status and the ability to suspend (sleep mode). The program simply accesses the /proc/acpi or /sysfs entries to get or set ACPI values. A computer running a Linux kernel from the 2.4.x or 2.6.x series with ACPI enabled is needed. It also supports various extensions for Toshiba, Asus, and IBM Thinkpad laptops.

Afick 'afick' is a multi-platform file integrity checker. It works by first creating a database that represents a snapshot of the essential parts of your computer system. You then run the script to discover all modifications made since the snapshot was taken (i.e. files added, changed, or removed). It shows new, deleted and changed files (rights, owner, size, content).

Alarm Pinger Alarm Pinger (apinger) is a little tool which monitors various IP devices by simple ICMP echo requests. Unlike most Perl or shell script tools, it does not spawn processes or use much CPU time, and is ideal for when one wants continuous monitoring and fast response upon target failure. It supports both IPv4 and IPv6. Alarm Pinger is configurable via $sysconfdir/apinger.conf file. The configuration file contains definitions for alarms, targets and various parameters. It does need root privileges to start (to create raw sockets), but will drop them before sending or receiving any packets.

Alist Alist is a program that collects hardware and software information about systems and stores it in a database for users to browse and search via a Web interface. The program consists of three parts: a client portion that collects the information, a daemon that receives data sent from clients, and a CGI that displays and lets you search for information.

Am-utils The Berkeley Automounter, Amd, maintains a cache of mounted file systems, and lets users dynamically control which file system to mount with selectors. Selectors, which may be combined, allow decisions of the form "hostname is this," or "architecture is not that." Amd also supports numerous file system types, including NFS, UFS and the novel program file system. The combination of selectors and multiple file system types means that identical configuration files can be used on all machines. Amd will not hang if a remote server goes down, and can determine when a remote server has become inaccessible and mount replacement file systems when they become available.

Analog It is fast, easy to install and run, very flexible, features multi-language support, produces attractive output, can be run directly or from a form interface, understands any logfile format, and works on any operating system. It can report in 36 languages.

Andatool 'andatool' displays in real time how often regular expressions match with the lines written to a logfile. This shows (for example) which firewall rules get triggered the most.

Arpalert 'arpalert' listens on a network interface, catches all conversations of MAC address to IP request, and compares the MAc addresses it detected with a pre-configured list of authorized addresses. If the address is not on this list, arpalert launches an alert script with the MAC address and IP address as parameters. 'arpalert' can run in daemon mode and is very fast (low CPU and memory consumption). It responds at signal SIGHUP (configuration reload) and at signals SIGTERM, SIGINT, SIGQUIT and SIGABRT (Kwhere it stops itself).

Ascpu 'ascpu' is an X windows applet with AfterStep look which displays the current CPU load (user/system/nice) and calculates the average load. It features multiple options for customization.

Asmem Asmem is a a memory utilization monitor. It shows the current amount of memory and swap space, and the free amounts of those. Bars represent graphically the different types of memory. It has an AfterStep look and feel. The current version compiles on the Hurd.

Atchange When the atchange program is running, it watches one or more files. When any of those files changes, the program will wake up and do any actions you want. Tasks such as modifying and compiling a program, modifying a data file and using it, or editing atext and typresetting it can be automated with a single typed command such as: atchange myprogram "compile program" By setting up 'atchange' once before starting a repetitive task, one can avoid hundreds of mouse movements.

Atkins 'atkins' examines variables, tables, and linked lists in the running kernel. Subcommands can be entered to show formatted kernel administration of processes, open files, incore inodes, page cache buffers, sockets, etc. Memory dumps can be shown using virtual or physical addresses, or using addresses within user space of a particular process. Furthermore stack backtraces can be printed e.g. to determine the reason why a particular process is currently in a wait-state. Note that atkins requires a certain level of knowledge about the Linux kernel.

Atop Atop is an ASCII full-screen performance monitor similar to the 'top' command. For a given interval, it shows system-level activity related to the CPU, memory, swap, disks and network layers, and for every active process it shows the CPU utilization in system and user mode, the virtual and resident memory growth, priority, username, state, and exit code. It also shows process level activity for processes which finished during the last interval. Atop shows only the active system-resources and processes, and only the deviations since the previous interval. Unfortunately, the standard kernel does not maintain counters about the number of disk and network accesses issued per process. Kernel patches will be made available to add these counters; the current version of atop can already display them.

Atsar 'atsar' detects performance bottlenecks on GNU/Linux systems. It is similar to 'sar' on other *NIX platforms. Atsar shows what is happening on the system at a given moment by supplying an interval as command-line argument; however, it also keeps track of the past system load by maintaining history files from which users can extract information. The package gathers statistics about CPU utilization, disks and disk partitions, memory and swap, tty's, TCP/IP (v4/v6), NFS, and FTP/HTTP traffic.

Authfail 'authfail' is a tool for adding IP addresses to an ACL when entities from those addresses attempt to log into a system, but cause authentication failures in auth.log. It reads data from auth.log in real time and adds the IP into netfilter with a DROP/REJECT policy.

Auto nice daemon The auto nice daemon (AND) periodically activates itself and renices jobs according to priority and CPU usage. Jobs owned by root are left alone. Jobs are never increased in their priority. The renice intervals, the default nice level, and the activation intervals can all be adjusted. A priority database stores user/group/job tuples along with their renice values for three CPU usage time ranges. Negative nice levels are interpreted as signals to be sent to a process, triggered by CPU usage; in this way, browser sessions running amok can be killed automatically. The strategy for searching the priority database can be configured.

Auto-autofs 'auto-autofs' searches block devices (via /proc) and disk partitions (via fdisk) and generates an automounter map. It can also work as an automounter program. It also generates an HTML file for easy access to the devices, so users can mount (and umount) partitions by clicking on a link.

AutoScan 'AutoScan' is an application designed to explore and manage your network. Entire subnets can be scanned simultaneously without human intervention. It features OS detection, automatic network discovery, a port scanner, a Samba share browser, and the ability to save the network state.