Must have apps for server admins!
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htop -

htop is an lightweight interactive process-viewer (really similar to a task manager) for Linux operating systems, Mac OS X and even BSD. It is a text-mode application for the console and terminals. The only requirement of htop is the package ncurses. Compared to top, htop is way more convenient and really a handy application.

htop displays the load per core and the avg system load. Moreover you can see all tasks sorted by the order of your choice. htop also displays the system uptime and used RAM. Below the RAM usage you can see Swap usage. At the bottom are shortcuts for important commands and functions of htop. For deeper configuration you can modify the htop configuration file created in your home directory in the folder ".config".

[Image: htop-1.0-screenshot.png]
(From the official htop homepage

tmux -

tmux is a terminal multiplexer for Linux, Mac OS X and BSD. A terminal multiplexer is a program that allows you to run multiple terminals in a single session. Not only that! tmux allows you to detach and reattach to sessions with terminals. This way you can leave programs running in the terminals in the background without being logged in into your server. tmux is the best alternative to the program called screen. It requires the packages libevent and ncurses.

In the picture below you can see a huge amount of terminals running in tmux used for a whole lot of things like IRC, a music player, development and so on... As well as htop tmux is a text-mode application for the console and terminals. You control it with key shortcuts and a few commands. It is better than screen in a lot of ways.

[Image: ss-tmux3.png]
(From the official tmux homepage)


iftop -

iftop monitors traffic on a network interface (adapter) and displays all connections and their bandwidth usage in a table. You could say it's top/htop but for network connections. Again this is a text-mode application for consoles and terminals. It requires libpcap and libcurses to work.

[Image: iftop_normal.png]
(From the official iftop homepage


Feel free to post your must have applications with a description, if possible a screenshot and links to guides, etc... below. But don't post what has been already posted. Try to be as clear as possible about what the application does and why it is a must have/important application for a server administrator.

Thank you!
atop -

atop - advanced interactive full-screen performance monitor, written for Linux. Is an analogue of top, but unlike it displays only the new changes on the active system processes. Allows you to monitor usage CPU, RAM, HDD, computer network, as well as the distribution of loads on the handles processes. Is a handy tool for system administration.

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(From the official htop homepage
byobu -

byobu - Byobu is a GPLv3 open source text-based window manager and terminal multiplexer. It was originally designed to provide elegant enhancements to the otherwise functional, plain, practical GNU Screen, for the Ubuntu server distribution. Byobu now includes an enhanced profiles, convenient keybindings, configuration utilities, and toggle-able system status notifications for both the GNU Screen window manager and the more modern Tmux terminal multiplexer, and works on most Linux, BSD, and Mac distributions. Basically, its like the earlier suggested tmux only with a more featured default configuration and a ton of easy to use setup tools.

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iotop is nice tool

if you're paranoid server admin, might netcat-openbsd and tcpdump would work too Smile

BTW does anyone know such tool that disconnects other app connections? That would be really helpful!!
There's no light if you don't make any
If you're ever needing to test a SMTP server, you're going to want SWAKS, the Swiss Army Knife of SMTP. It's a giant Perl script that you can get everything you need to know from with a --help argument. I've set up countless MX servers and this is an invaluable tool in the process of testing and at times, simple automations.
(2014-06-16, 3:48:33 am)snowflakes Wrote:  If you're ever needing to test a SMTP server, you're going to want SWAKS, the Swiss Army Knife of SMTP. It's a giant Perl script that you can get everything you need to know from with a --help argument. I've set up countless MX servers and this is an invaluable tool in the process of testing and at times, simple automations.

Thanks for that!
I'd add Icinga/Nagios for monitoring automation.

What about logs centralization? Has anybody used an open source alternative to Splunk ?
powertop incase you think some device is chewing off more power.
man 8 powertop

shellinabox if you want a nice gui for openssh.
i use it pretty much when i am too lazy to command line ssh into my debwrt mips boxes.
Nagios is a powerful monitoring system that enables organizations to identify and resolve IT infrastructure problems before they affect critical business processes.

Wireshark is a network protocol analyzer, also known as a network sniffer. It’s similar to other tools such as tcpdump but with a graphical interface and the ability to more easily filter traffic by type, source and destination addresses and ports. Wireshark can run on all of the popular operating systems, it uses libpcap on Linux to capture packets and WinPcap on Windows. You can use it to troubleshoot network and application issues or simply to monitor what traffic there is on the network.

On a security issue note, any snoop tool can only sniff packets going to and from your machine. To change that you would have to set up your router in promiscuous mode or plug your machine into a hub, router, or switch in your network.

On a busy network the output from Wireshark will go by on the screen very fast. You can log the traffic into a .pcap file for review at a later time.

CSF is a suite of scripts which provide firewall, login, intrusion detection, and more. The firewall is essentially a front end to iptables with plenty of additional useful features. Firstly, it uses the iptables firewall, allowing you to implement rules without needing to understand the details and syntax of iptables. This allows you to secure your server by locking down both inbound and outbound traffic. For instance you can set up your server to only allow SSH connections on port 22 from and to deny all other requests to port 22.

CSF is also able to actively block attacks. So, if you are allowing into port 22 and someone compromises that server, if they then try to SSH into your server, despite being allowed in the firewall, if they fail to log in a set amount of times within a set period of time, their source IP address will be blocked in the firewall temporarily. If enough temporary blocks occur they can be blocked permanently as an attacker. This works for a lot more than just SSH, it also works for failed logins to web pages protected with htpasswd, Exim SMTP authentication, Mod_Security failures, or even FTP from vsftpd/proftpd/pure-ftpd.

While CSF can be used on a standalone Linux server, it has a GUI component if used on a WHM/cPanel server. It can be configured and managed via WHM, rather than through the command line, which is great as WHM hosting is very popular.

MySQL Tuner:
MySQL Tuner is a Perl script which can be used to quickly examine MySQL on your server and to provide suggestions to increase performance and stability.

While the advice provided by the script is generally good, only put changes in that you understand and know what they are actually doing. If you look up the MySQL documentation for the various variables it should explain to you how they work. Basically, you should perform changes on a test server if possible and not straight onto a production server; some changes will require a MySQL restart, potentially leading to downtime. Poorly set variables can also reduce performance and stability.

Metasploit Community Edition:
Metasploit Community Edition allows you to simulate attacks on your network to uncover security issues. Features include the ability to discover network assets, conduct basic penetration tests and exploit individual vulnerabilities.

OpenVAS is an open source Vulnerability Assessment System that offers a selection of tools and services for vulnerability scanning and vulnerability management. The security scanner feeds off an online database of over 30,000 network vulnerability tests and is updated regularly.

Retina Network Community:
Retina Network Community is a free vulnerability scanner for up to 256 IPs that offers powerful vulnerability assessment across operating systems, applications, devices and virtual environments within your network using a comprehensive vulnerability database that is updated regularly.

Postfix Admin:
Postfix Admin is a web based interface used to manage mailboxes, virtual domains and aliases. It also features support for vacation/out-of-the-office messages.

It requires PHP, Postfix and one of MySQL or PostgreSQL.

Taken from various sources on the internet
Thank you FreeVPS and ZXPlay for VPS 7 and 19

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Don't PM me for support, use an appropriate forum to ask for support
Mind the copy and paste rules! Unlike most of who posted here I actually have written my own descriptions out of the information I know and that was available online.
Oops... Sorry, my purpose is to let you know about a bunch of application that you may need. Will never happen anymore Sad
Thank you FreeVPS and ZXPlay for VPS 7 and 19

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Don't PM me for support, use an appropriate forum to ask for support

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