Posts Tagged ‘server desktop’

How to start a process in background and keep it running after the console / terminal is closed on Linux and FreeBSD

Tuesday, November 29th, 2011

The classical way to keep a process running in background after log out of a shell is using screen
Anyways using screen is not the only way to detach a running process , GNU / Linux and BSDs (Free, Open, Net BSDs) had a command nohup which aim is to run a command immune to hangups, with output to a non-tty

Let’s say one wants to keep track (log) constantly ICMP traffic to a certain host with ping command on a UNIX server / desktop which doesn’t have the screen manager … terminal emulation program installed. Achieving this task is possible with nohup cmd by backgrounding the ping process, like so:

guoi@host:~$ nohup ping google.com >ping.log &[1] 45931hipo@host:~$ nohup: ignoring input and redirecting stderr to stdout

Afterwards even after closing up the opened ssh session or console (tty) / terminal (pts) on which the ping process is background nohup prevents the ping to be sent kill SIGNAL so the process continues running in the background.

Later on to check in real time the statistics of the continuous ICMP ping requests tail, less, or cat can be used for example watching the tail:

hipo@host:~$ tail -f ping.log
64 bytes from fx-in-f106.1e100.net (74.125.39.106): icmp_req=562 ttl=51 time=44.0 ms
64 bytes from fx-in-f106.1e100.net (74.125.39.106): icmp_req=563 ttl=51 time=43.8 ms
64 bytes from fx-in-f106.1e100.net (74.125.39.106): icmp_req=564 ttl=51 time=43.3 ms
64 bytes from fx-in-f106.1e100.net (74.125.39.106): icmp_req=565 ttl=51 time=43.1 ms
64 bytes from fx-in-f106.1e100.net (74.125.39.106): icmp_req=566 ttl=51 time=43.4 ms
64 bytes from fx-in-f106.1e100.net (74.125.39.106): icmp_req=567 ttl=51 time=43.6 ms

I’m using Linux / BSD for quite a lot of time and never before put in use the nohup cmd I guess there are more ppl who never heard of this handy UNIX basic command. Hope I’m not the only one who never heard about it and its useful knowledge to someone out. Cheers 😉

Monitor General Server / Desktop system health in console on Linux and FreeBSD

Tuesday, October 4th, 2011

slurm-output-monitoring-networking
saidar
is a text based ncurses program to display live statistics about general system health.

It displays in one refreshable screen (similar to top) statistics about server state of:
CPU, Load, Memory, Swap, Network, I/O disk operations
Besides that saidar supports a ncurses console colors, which makes it more funny to look at.
Saidar extracts the statistics for system state based on libgstrap cross platform statistics library about pc system health.

On Debian, Ubuntu, Fedora, CentOS Linuxes saider is available for install straight from distribution repositories.
On Debian and Ubuntu saidar is installed with cmd:

debian:~# apt-get install saidar
...

On CentOS and Fedora saidar is bundled as a part of statgrab-tools rpm package.
Installing it on 64 bit CentOS with yum is with command:

[root@centos ~]# yum install statgrab-tools.x86_64

Saidar is also available on FreeBSD as a part of the /usr/ports/devel/libgstrab, hence to use on my FreeBSD I had to install the libgstrab port:

freebsd# cd /usr/ports/devel/libstatgrab
freebsd# make install clean

Here is saidar running on my Desktop Debian on Thinkpad in color output:

debian:~# saidar -c

Saidar Linux General statistics Screenshot

I've seen many people, who use various shell scripts to output system monitoring information, this scripts however are often written to just run without efficiency in mind and they put some let's say 1% extra load on the system CPU. This is not the case with saidar which is written in C and hence the program is optimized well for what it does.

Update: Next to saidar I recommend you check out Slurm (Real Time Network Interface Monitor) it can visualizes network interface traffic using ascii graph such as on top of the article. On Debian and Ubuntu Slurm is available and easily installable via simple:
 

apt-get install –yes slurm