sudo inside a cron job

If some reasons you need to use sudo in a cron job, for example if you use ltib (Linux Target Image Builder)  in a nightly build script, you may realize that it does not work by default and you may get the message: sudo: sorry, you must have a tty to run sudo In that case simply run visudo and comment out the line: #Default requiretty Jean-Luc Aufranc (CNXSoft)Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011. http://www.cnx-software.com

Replacing tabs by spaces in vi

In order to have code formatting consistency, we may choose to use only tabs or only spaces in the source code. We chose to only use spaces since that makes sure the code will be properly formatted in any text editor. In order to create 4 spaces while pressing tabs in vi, edit your vi settings: vi ~/.vimrc and add the 3 lines below to your config file set tabstop=4 set shiftwidth=4 set expandtab The next time you’ll use vi, pressing the tabulation key will create 4 spaces. However, in some cases, e.g. Makefile, you may still need to use real tabs. Just press Ctrl+V then tab to create a real tab. Jean-Luc Aufranc (CNXSoft)Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011. http://www.cnx-software.com

Software profiling in embedded systems with O-profile

What is o-profile? See the description below extracted from http://oprofile.sourceforge.net/, o-profile official website OProfile is a system-wide profiler for Linux systems, capable of profiling all running code at low overhead. OProfile is released under the GNU GPL. It consists of a kernel driver and a daemon for collecting sample data, and several post-profiling tools for turning data into information. OProfile leverages the hardware performance counters of the CPU to enable profiling of a wide variety of interesting statistics, which can also be used for basic time-spent profiling. All code is profiled: hardware and software interrupt handlers, kernel modules, the kernel, shared libraries, and applications. OProfile is currently in alpha status; however it has proven stable over a large number of differing configurations; it is being used on machines ranging from laptops to 16-way NUMA-Q boxes. As always, there is no warranty. Why don’t we use gprof? For embedded system , we do not use gprof (the GNU profiler) because it …

Finding and fixing memoy leaks in your software

Memory leaks will cause your device to crash after a period of time once it runs out of memory. A quick way to find out if your application has memory leak(s) is too monitor it with top: PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND 1       root       15   0   2156    668  572 S     0           5 .0      0:00.14         application If you see the %MEM increase over time for no particular reasons, then you’ve got a memory leak. However, it might be tricky to isolate where the issue occurs exactly. The first thing to do is the review your source code for the following: Malloced memory is always freed fopen is always followed by fclose, and open by close scandir calls are properly freed Threads are properly terminated with pthread_cancel & pthread_join or pthread_detach, etc… If after a code review you cannot find the reason for the memory leak, use the following …

Mounting a JFFS2 image in a Linux PC

We often use JFFS2 binary images for embedded system, generating them with mkfs.jffs2. In some instances, it could also be good to mount a jffs2 image into your PC to modify it directly. To do that,  type the following commands as root in a linux shell: modprobe mtdcore modprobe jffs2 modprobe mtdram modprobe mtdchar modprobe mtdblock dd if=image-jffs2 of=/dev/mtd0 mount /dev/mtdblock0 mnt If your image is larger than the default kernel size (4MB in my case), you can try to adjust the mtdram device size with the total_size parameters. when inserting the mtdram module, e.g.: modprobe mtdram total_size=8096 where total_size is expressed in KB Further details can be found @ http://www.handhelds.org/hypermail/familiar/62/6232.html Jean-Luc Aufranc (CNXSoft)Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011. http://www.cnx-software.com