Posts Tagged ‘cmd’
Thursday, December 15th, 2011 
I’m writting some game reviews and movie reviews, every now and then and therefore being able to capture a fullscreen running program like let’s say mplayer or vlc or some full screen running game is something I really need.
The usual PrtScr button which normally works to prepare screenshots in GNOME or KDE, however is not working if the root window handler is being passed to a different program than the Window Manager and pressing it while inside of many older programs or applicationsdoes not produce a print screen of the current screen.
Anyways I found a hack to this using the good old ImageMagick – import command line screenshotting program.
To take a screenshot of a certain program run from gnome-terminal or konsole using import cmd its possible to use a quick one liner which will take a snapshot of the root Window the started program will use.
Let’s say you want to make a screenshot of the entry screen of the FreeDOOM (DooM 3d shooter classical game arcade free Software Alternative).
Launch gnome-terminal or konsole , xterm , depending on the GUI environment you use and issue the commands:
debian:~$ ( sleep 15; import -window root my_desired_screenshot_name.png ) &
debian:~$ freedoom
The first command will launch import after a sleep of 15 secs and therefore will screenshot the active window which will be at focus after 15 seconds, where the & sign will background it and the second one will launch FreeDooM . You will have to wait for a certain secs and switch to the exact screen you will want to screenshot.
If you want to screenshot some game scene that will appear in 20 minutes change above sleep 15 cmd to be to something like sleep 180
That method can be used for screenshotting any other program running on fullscreen, the method is a bit inflexible as you will have to adjust a timing but it works fine 😉
Tags: bit, Button, classical game, cmd, Desktop, desktop environment, exact screen, first command, FreeDooM, fullscreen, game arcade, game reviews, game scene, Gnome, GNU, gnu linux, gui environment, how to take a screenshot, ImageMagick, import, import command, import window, launch, Linux, mplayer, PrtScr, root, root window, running game, screen, screenshot, shooter, sign, sleep, software, something, timing, VLC, xterm
Posted in FreeBSD, Linux, Linux and FreeBSD Desktop, Various | No Comments »
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 😉
Tags: aim, BSDs, cheer, Cheers, cmd, com, Desktop, detach, Free, fx, gnu linux, google, Hope, host, ICMP, icmp ping, log amp, manager, msi, net, nohup, Open, ping, ping command, ppl, real time, req, screen, server desktop, Shell, someone, ssh, ssh session, stderr, terminal, terminal emulation program, time, tty, unix server, useful knowledge
Posted in FreeBSD, Linux, System Administration | 1 Comment »
Wednesday, September 28th, 2011 
To find out which programs are causing the most read/write overhead on a Linux server one can use iotop
Here is the description of iotop – simple top-like I/O monitor, taken from its manpage.
iotop does precisely the same as the classic linux top but for hard disk IN/OUT operations.
To check the overhead caused by some daemon on the system or some random processes launching iotop without any arguments is enough;
debian:~# iotop
The main overview of iostat statistics, are the:
Total DISK READ: xx.xx MB/s | Total DISK WRITE: xx.xx K/s
If launching iotop, shows a huge numbers and the server is facing performance drop downs, its a symptom for hdd i/o overheads.
iotop is available for Debian and Ubuntu as a standard package part of the distros repositories. On RHEL based Linuxes unfortunately, its not available as RPM.
While talking about keeping an eye on hard disk utilization and disk i/o’s as bottleneck and a possible pitfall to cause a server performance down, it’s worthy to mention about another really great tool, which I use on every single server I administrate. For all those unfamiliar I’m talking about dstat
dstat is a – versatile tool for generating system resource statistics as the description on top of the manual states. dstat is great for people who want to have iostat, vmstat and ifstat in one single program.
dstat is nowdays available on most Linux distributions ready to be installed from the respective distro package manager. I’ve used it and I can confirm tt is installable via a deb/rpm package on Fedora, CentOS, Debian and Ubuntu linuces.
Here is how the tool in action looks like:
The most interesting things from all the dstat cmd output are read, writ and recv, send , they give a good general overview on hard drive performance and if tracked can reveal if the hdd disk/writes are a bottleneck to create server performance issues.
Another handy tool in tracking hdd i/o problems is iostat its a tool however more suitable for the hard core admins as the tool statistics output is not easily readable.
In case if you need to periodically grasp data about disks read/write operations you will definitely want to look at collectl i/o benchmarking tool .Unfortunately collect is not included as a packaget for most linux distributions except in Fedora. Besides its capabilities to report on servers disk usage, collect is also capable to show brief stats on cpu, network.
Collectl looks really promosing and even seems to be in active development the latest tool release is from May 2011. It even supports NVidia’s GPU monitoring 😉 In short what collectl does is very similar to sysstat which by the way also has some possibilities to track disk reads in time. collectl’s website praises the tool, much and says that in most machines the extra load the tool would add to a system to generate reports on cpu, disk and disk io is < 0.1%. I couldn’t find any data online on how much sysstat (sar) extra loads a system. It will be interesting if some of someone concluded some testing and can tell which of the two puts less load on a system.
Tags: action, bottleneck, CentOS, cmd, description, Disk, disk utilization, drive, drive performance, drop, eye, generating system, GNU, gnu linux, handy tool, interesting things, Linux, linux server, linux top, linuxes, manager, manual states, most linux distributions, overhead, package, performance drop, performance issues, pitfall, program, random processes, recv, repositories, resource statistics, server performance, sIf, system, system resource, tool, Ubuntu, versatile, versatile tool, vmstat
Posted in Linux, System Administration, Various | 5 Comments »
Monday, September 26th, 2011 
A friend of mine gave me a VCD with some coptic Orthodox Christian exorcism, where there pope was chasing some evil spirits from possessed muslims who came to the Coptic Orthodox Church in egypt. The video was made to be in VCD and as you can expect this did not worked out of the box with Totem and VLC out of the box.
Putting in the VCD video inside my cdrom poped up an error like the one in the header of the post.
In order to make the video play I had to use the old school and now a bit obsolete mplayer.
Hence in order to play the VCD on Debian Linux I had to install mplayer and w32codecs packages first e.g.:
debian:~# apt-get update && apt-get install mplayer w32codecs
Second to play the video from gnome-terminal, I had to switch to the mounted cdrom location /media/cdrom0 and launch the video with mplayer cmd like so:
debian:~$ cd /media/cdrom0/vcd
debian:/media/cdrom0/vcd$ mplayer vcd://2
...
In some cases it might be necessery to play the video with mplayer command like:
debian:/media/cdrom0/vdd$ mplayer vcd://2 vcd://3
Watching it with mplayer from console has some downsides as I couldn’t make the fast rewind work, but still it’s way better than nothing.
Too bad in Debian Squeeze 6 gmplayer is no longer installable. The gmplayer can probably be installed if mplayer is compiled from source, but I’m too lazy to try it out.
I’ve red also in some forums online that gxine is capable of playing the VCD play nice, but I couldn’t install it from my existing Debian repositories so I did not give it a go.
Tags: cd media, cmd, codecsSecond, command, coptic orthodox christian, coptic orthodox church, Debian, debian cd, debian linux, debian repositories, ERROR, evil spirits, exorcism, fast rewind, gmplayer, Gnome, gxine, location, mine, mplayer, muslims, necessery, old school, online, order, poped, post, rewind, squeeze, totem, update, VCD, vdd, video, video play, VLC, way, work
Posted in Entertainment, Everyday Life, Linux Audio & Video, Various | 1 Comment »
