Though there’s not much choice available as far as apps for Linux admin are concerned, but still there are few useful. I tried hereby compiling list of 5 such apps which can be helpful for us but its definitely possible that I didn’t come through some awesome app which you are aware about, in such case, requesting you to please put a comment about it.

1. ConnectBot

This one is my favorite, may be because I use this frequently. ConnectBot is a powerful open-source Secure Shell (SSH) client developed by Kenny Root and Jeffrey Sharkey. It can manage simultaneous SSH sessions, create secure tunnels, and copy/paste between other applications. This client allows you to connect to Secure Shell servers that typically run on UNIX-based servers. This of course can’t replace you the experience of using your PC/Laptop but in case where you are on the move and needs to get inside your server fast, this is must have. You can get more info about it from here.

2. VNC® Viewer

VNC® Viewer control a computer anywhere in the world from your Android device! I have used it few times and it worked flawlessly. You can run applications, change settings, and access data exactly as you would be permitted to do were you sitting in front of it, and using the keyboard and mouse.

3. ServerUp

A good to have monitoring app for any Sys Admin. ServerUp allows you to check the status of your network and web servers. ServerUp is configurable to check the status as often as you would like. Looks like Android market right now lacks good monitoring apps using which you can keep eye on your network/servers and even at this moment, the apps which are there are not fully tested and kind of bit unstable.

4. DropBox

Who don’t know about this? Though not a specific app for admins out there but can be helpful to keep your important notes/files in sync. I usually keep server related notes, info etc in text files and dropbox does the duty of keep it up to date everywhere, be it PC, web or android phone. After you install Dropbox on your computer, any file you save to your Dropbox will automatically save to all your computers, your Android device, and even the Dropbox website! With the Dropbox app, you can take everything that matters to you on the go. Another worthy app in this space is ES File Explorer.

5. AndFTP

AndFTP is a FTP, FTPS, SCP, SFTP client. It can manage several FTP configurations. It comes with both device and FTP file browser. It provides download, upload, synchronization and share features with resume support. Though I used it once when I needed to upload a file to a remote server through FTP urgently and fortunately file was there in my phone. AndFTP worked as expected.

Do you know or aware about any other app which is useful for Admin community? Please put a comment about it.

Here are quick steps to install it on CentOS 5.2 box (upgraded from 5.0 release).

Try to install in easy way:

$ yum install ntop

Most probably yum get failed for missing dependencies such as rrdtool package. If this is the case, download and install this package manually:

$ cd /usr/src
$ wget http://dag.wieers.com/rpm/packages/rrdtool/rrdtool-1.2.23-1.el5.rf.i386.rpm
$ rpm -ivh rrdtool-1.2.23-1.el5.rf.i386.rpm --nodeps

I’ve used –nodeps option in rpm command to ignore any dependencies. Yum will take care of that, we just need rrdtool as of now.

now try again with yum, ntop should be installed successfully:

$ yum install ntop

Configure ntop to suit your requirements, such as which network interface should it monitor and on which port (http port) should it display graphical interface.

$ vim /etc/ntop.conf

Save the file and start ntop with specifying the path of conf file:

$ ntop @/etc/ntop.conf

you can also handle it with more easy ‘service ntop start/stop’ commands.

ntop will start collecting network stats and you can view the graphs and further configure its graphical interface: http://localhost:3000/

You may also like to read:
* 5 steps to secure your Linux Server
* Ensuring secure access to production Linux Servers
* Bash script to backup essential log files in Linux
* Quickly change your ssh port from defualt 22 to something higher
* SSH port forwarding from remote to local machine
* Save root or user history to check later
* Install and configure denyhost to prevent brute force attacks

In Nagios screen it shows:

NRPE: Unable to read output.

Checking from the machine itself, NRPE is giving correct version but throwing same error for any other checks:

$[root@domU:/usr/local/nagios/libexec] ./check_nrpe -H localhost
NRPE v2.8
 
$[root@domU:/usr/local/nagios/libexec] ./check_nrpe -H localhost -c check_load
NRPE: Unable to read output

After further digging, I’ve found he installed Nagios-plugins using yum which placed plugins files in some different location then desired by NRPE.

Then I installed nagios-plugins manually:

$ cd /usr/src
$ wget http://osdn.dl.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.6.tar.gz
$ tar xzf nagios-plugins-1.4.6.tar.gz
$ cd nagios-plugins-1.4.6
$ ./configure --without-mysql
$ make
$ make install

The problem is resolved immediately.

This quick copy and paste howto explains steps needed to setup server and multiple nodes. These steps are tested in CentOS 5 Server but Please check respective documentation to make sure this will work for you as well.

Step 1. Prepare Server machine. For quick installation and dependency resolution, you can install DAG repository:

$ rpm -Uhv http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm

Step 2. Install munin (server) and munin-node (node) on this machine:

$ yum install munin munin-node

Step 3. Setup a directory to store munin generated htmls, you can create a directory in your server DocumentRoot or in munin directory itself. Here we create it in munin’s directory:

$ cd /etc/munin
$ mkdir html
$ chown munin:munin html -R

Step 4. If in previous step, you created a directory in your web server root, then you dont need to set an alias, else if you did the exact whats written in above step, create an alias:

$ vi /etc/httpd/conf/httpd.conf
 
Alias /server-health/ "/etc/munin/html/"
<Directory "/etc/munin/html">
AllowOverride None
Options None
Order allow,deny
Allow from all
</Directory>

Step 5. Configure munin for monitoring localhost (you are already in /etc/munin directory):

$ vi munin.conf
 
htmldir /etc/munin/html
[localhost]
address 127.0.0.1
use_node_name yes

here we set the html directory and section for local machine. Feel free to change ‘localhost’ to any meaningful name like Monitoring Server etc. You can further read the file for more options.

Step 6. Start munin service:

$ chkconfig munin-node on
$ service munin-node start

Step 7. Restart your web server and then access the munin page from your browser by pointing it to http://localhost/server-health/. You can also password protect the munin page by using .htaccess or inserting rules in your httpd.conf file but its optional.

You should be able to view various parameters/values/trends related to disk,network,apache,mail etc of your local machine/server via browser. Let us configure multiple nodes now:

Step 8. SSH to any other machine/ server and install DAG repository as described in Step 1 and then install the munin node:

$ yum install munin-node

Step 10. Configure the node to allow our main server get input from this machine. For this purpose, we need to add ‘Allow IP ADDRESS’ line in config file. Note that there’s already a Allow line which allow localhost to get values, we just need to add another line for server:

$ vi /etc/munin/munin-node.conf
 
allow ^192\.168\.0\.1$

Here 192.168.0.1 (change it as per your settings) is the IP of server machine, written in regex form which is required here.

Step 11. Start the node now:

$  chkconfig munin-node on
$ service munin-node start

Now configure the Server to monitor the above machine:

Step 12. Goto Server machine and update munin.conf and add a new section:

$  vi /etc/munin.conf
 
[App_Server]
address 192.168.0.5
use_node_name yes

Here, App_Server is the name (you can write any), and 192.168.0.5 is the IP address of the machine in which we configured munin-node in Step 9 to Step 11.

After a while, Check you browser and munin should include the update from node machine.

Common Issues:

1. No values/stats are displayed or blank.
Please verify that munin-node service is running at machine. Verify it by telnet from machine itself:

$ telnet localhost 4949

You should see munin prompt here, write fetch cpu and press ENTER. You should see various values related to your cpu. If you are not able to telnet to port 4949 (munin port) then possibly munin-node is not running or your iptable (firewall) or SELinux policy is preventing its usage.

After checking from localhost, go to Server machine and try to telnet from there:

$ telnet 192.168.0.5 4949

You should get munin prompt and see values after issuing fetch cpu command there. If not, then firewall/selinux is preventing access this port or you didnt allowed this server from your munin-node.conf to get updates.

2. Why not compile from source?
Thats the best idea but when I tried the same, I got lots of perl modules dependencies/compile errors. Though, I managed to get its working but for a quick setup, yum is your friend.

3. I do not need all these values coming in graphs.
You can remove any plugin for which you do not want graph. Plugins are stored in /etc/munin/plugins directory and configured in plugins.conf. Configure these as per your requirements.

You may also like to read:
* 5 steps to secure your Linux Server
* Ensuring secure access to production Linux Servers
* Bash script to backup essential log files in Linux
* Quickly change your ssh port from defualt 22 to something higher
* SSH port forwarding from remote to local machine
* Save root or user history to check later
* Install and configure denyhost to prevent brute force attacks