The use of Unix in embedded computer systems such as networking equipment, mobile phones, media players, set-top boxes, etc.

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How to check my account on embedded linux without “/etc/passwd”?

On some embedded linux systems, there is no /etc/passwd file and /etc directory is not writable (which means I cannot set user account and password?). Then what is my (default) account name and ...
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1answer
41 views

How to know free disk size witout df command? [on hold]

Is it possible to check free disk size in Linux without using command lines such as df? Since my host machine is embedded Linux, there are no direct command lines that show free disk size.
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2answers
374 views

Adding Buildroot Package

I'm trying to add a package to buildroot, but I'm not having much success. The package I'm trying to add is an autotools package called scew. I've followed the buildroot guidelines about adding ...
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1answer
410 views

Debian and Systemd: breaking ordering cycle error

I'm a new embedded developer I'm trying to make systemd 37 work with freescale vybrid board (A5 and M4) running on linux-3.0 After boot with some breaking ordering cycle error, I check with ps ...
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42 views

Why is my swap not being activated automatically via fstab?

I've got a Linux embedded system that I'm experimenting with (the Elektor Embedded Linux Made Easy board, based on the GNUBLIN http://en.gnublin.org/index.php/GNUBLIN-Elektor). I'm using the 3.3 ...
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1answer
23 views

Late running of scripts during bootup, ending with a reboot without the login prompt

I'm making a special "installer" for an embedded system where I'd like the kernel to boot up, execute a set of things very late in the process where the peripherals have been set up and then reboot ...
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1answer
323 views

How to change hard disk spin-down time on my WD MyBook Live?

I have a 2TB Western Digital MyBook Live. It works quite well and provides a web-based administration interface. There is an option to either enable or disable power saving mode, which spins down the ...
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22 views

redirecting output of /dev/fb0 to /dev/fb2

I am using IMX6 Saberauto board on Linux OS. I have 2 displays primary is HDMI and secondary is LVDS. I want to run 2 applications. One QT on primary display, which I am able to do. Second ...
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47 views

Can't login using serial on ttyO0 - BeagleBone Black

I boot Beaglebone Black, connected to my desktop by serial. It was working great, until now. Beagle is booting, output shows up on the console, but at the end I can't log in. I can't type the login, ...
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1answer
353 views

Embedded linux LCD not calibrated

I have attached a new LCD to my embedded Linux device and when I run the system I found that it is shifted to the right. (the display starts from the middle of the LCD) I found 2 frame buffer drivers ...
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2answers
2k views

Why is GRUB 2 booting so slowly?

I have a small custom embedded Linux distribution (created with OpenEmbedded), which boots with GRUB 1.99. The aim is to have it start up fast. Currently it says: GRUB loading. for ~2+ seconds ...
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1answer
795 views

Mimo 2G USB Monitor and cheap computer (Raspberry Pi?)

I have a Mimo 2G USB Monitor (UM-710S I believe) which I got in college due to the lack of space for a real second monitor in the dorm. Now I don't really have a use for it, so I thought of ...
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26 views

How do I know from a BeagleBone Black if it is connected via USB (as a client/slave)?

BeagleBone Black has an USB port which allows the user to access it through ssh. In general, we could say that when you plug it to a PC, the PC is the USB host and the BBB is the USB client. On the ...
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2answers
46 views

tftpput in U-Boot: error: 'Access violation' (2)

I have enabled CONFIG_CMD_TFTPPUT in U-Boot, but I am not able to use it. I have set the serverip and ipaddr environment variables. When I use it as follows, it times out: u-boot# tftpput ...
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1answer
47 views

What are the disadvantages of uClibc?

I try to speed up my boot sequence, and somebody recommends to use the uClibc instead of Glibc. I've built an image with it, it gets smaller and faster to boot — but at which cost? Does anyone know ...
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40 views

cross compile embedded arm

I have the android 4.2.2 code in directory /home/sghPhone2 which compiles normal with make menuconfig but I need to compile a 4.4 kernel and possibly patch it but when I download the source from ...
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50 views

Unable to add serialport (nodejs module) when generating filesystem and cross-compiling tools for an ARM processor

I am using buildroot (version 2013.08.1) to generate the filesystem and cross compiling tools to implement embedded linux on a i.MX233 processor (ARM architecture). I add the serialport module by ...
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33 views

Is there a limit of GPIOs that can be used in Linux?

When it comes to use GPIOs, is there a limited number that can be used in Linux (except through the limitation of the physical availability/amount of the ports/pins) or is it theoretically possible to ...
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1answer
547 views

Attaching USB-Serial device with custom PID to ttyUSB0 on embedded

I'm attempting to get an FTDI USB-Serial device with a custom PID to automatically (or even manually) attach to ttyUSB%n, without much success. The device's normal VID/PID is 0403/6001. When ...
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35 views

What are the two head.S files in linux source ?

In the linux source there are two different head.S files located at: arch/arm/kernel/head.S arch/arm/boot/compressed/head.S What is the puprpose of each one and what is the order of there execution ...
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1answer
47 views

What are the two values in < > in a device tree .dts file ?

Following is the code snippet in a device tree file: flash@0 { compatible = "n25q128"; reg = <0x0>; spi-max-frequency = <50000000>; ...
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1answer
764 views

How to extract files from uImage?

Buildroot is generating Images for an embedded device where they should run on. This is working very well. In those Images the rootfs is included. Due to some research I'd like to look into that ...
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8 views

WAN interface using his own queues for QoS different that the provided by Linux

My Linux embedded system have a WAN interface with the default pfifo_fast qdisc attached to it. The web interface for configuring the system let the user configure three Queues for the WAN interface ...
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1answer
24 views

How do you ensure physical network interfaces always get the same interface name across reboots on an embedded Linux system?

For an embedded Linux system, if I have two or more network interfaces, how do I ensure that they always get the same interface names every boot In other words, I want, for example, eth0 to always ...
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99 views

Corruption-proof SD card filesystem for embedded Linux?

Recently we had a rather unpleasant situation with our customer - Raspberry Pi based "kiosk" used to display remote sensing data (nothing more fancy than a kiosk mode browser displaying a ...
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3answers
71 views

What are the minimum root filesystem applications that are required to fully boot linux?

It's a question about user space applications, but hear me out! 3 'applications', so to speak, are required to boot a funcitonal distro of Linux: Bootloader - For embedded typically that's U-Boot, ...
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3answers
49 views

Can I achieve functionality similar to interrupts in Linux userspace?

One of functionalities I miss the most from "small embedded" in Embedded Linux is the interrupts. A signal appears on a specific pin, or other interrupt source is triggered and whatever was done ...
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4answers
3k views

Shell command to read device registers?

On a single-board computer running Linux, is there a way to read the contents of the device configuration registers that control hardware? I think it would be a wrapper for inw(), more or less. I'm ...
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1answer
68 views

Why isn't sda1 showing up in dev and how can I fix that?

I have an embedded Linux device and I was trying to copy some files to it. I plugged in a USB stick, the dmesg shows that it was recognized, but for some reason /dev/sda1 never showed up. I'm trying ...
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2answers
76 views

Kernel does not skip bad blocks when mounting filesystem

I am developing for an embedded Linux application using friendlyARM's micro2440. It runs on a Samsung s3c2440 ARM processor and uses squashfs in its NAND flash. Recently, some flash blocks went bad. ...
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2answers
1k views

What does ifup do when “/etc/network/interfaces” has an invalid netmask address?

The interfaces file looks like below: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 192.168.0.130 netmask 250.255.255.0 gateway 192.168.0.254 As you can see ...
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2answers
63 views

live dd over a mounted read-only root partiton

I'm trying to conceive a firmware update mechanism for a Linux-based embedded system without an additional initrd/initramfs/whatever. From within the running system which has a read-only mounted root ...
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0answers
34 views

Get log from kernel while loading

There is a arm/omap2-based device without ethernet, UART ports. It has usb connection with host, numeric keyaboard, LCD display. There is working U-Boot and kernel images for this. I'm trying to ...
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1answer
82 views

How configurable is MPTCP?

I work on embedded Linux devices that usually have hard wired Ethernet as well as cell modem connections. If I were to use MPTCP would it be possible to easily configure the system to use eth0 all ...
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33 views

Interfacing with a custom camera in Linux on the beaglebone

I'm new to Linux development and need some pointers to help me get a camera (OV7670) working on a beaglebone running Debian. Using the camera capes as a guide, I've connected the camera to the GPMC ...
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28 views

Use Rsync with HTTP

Is it possible to use rsync with an HTML POST request? If so what would the rsync command look like? For example let's say using HTML5 I have this (bear with me going back to linux stuff): <form ...
3
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1answer
241 views

Which TCP congestion control algorithm is best for low speed radio modems?

On my project we have remote Linux nodes that communicate over the Internet via very low speed CDMA cell modems. The bandwidth on these modems is about 2kbyte/second and the RTT back to the server is ...
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3answers
159 views

Why does boot from SD card with my custom kernel result in “VFS: Cannot open root device”?

I'm using an embedded board ARM9 SAM9G25. I want to boot from SD card. When I build a linux kernel with a built-in rootfs (initramfs) then it boots. I want to separate the kernel from rootfs and I ...
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1answer
87 views

Why doesn't 'ar' work like the manpage says?

I'm trying to use 'ar' included in Debian Wheezy armel version of binutils and it doesn't seem to operate like on other systems I've encountered. Some sample output from the command-line: $ ar ...
3
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1answer
80 views

Booting using initramfs instead of uramdisk

I am working on Zynq Microzed board. It is booting perfectly with uramdisk.image.gz but I trying to boot it with initramfs.cpio. In this regard I have made following changes in header files of ...
2
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1answer
95 views

Most reliable way to check for connected client?

I have an embedded Linux OS developed from scratch using Yocto. This talks to a Windows XP/7 client. The embedded OS runs a DHCP server and gives an address to the client. The problem is that the ...
3
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1answer
240 views

How can one force a re-scan of an SDIO bus from Linux user space?

On an embedded Linux platform, I have a network adapter attached to an SDIO interface. There is no Card Detect signal on this particular bus. If for instance, I turn the network adapter power on or ...
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1answer
75 views

Conntrack TCP Timeout for state stablished not working

Im using a private IP address and I want to keep alive SNAT entries in my Router (Gateway) for at least two hours (some windows apps of my network are using TCP keepalive set to 2 hours). Gateway is a ...
0
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0answers
52 views

How can I make a configuration web page for a linux appliances? Any pre made solutions available?

I am putting together a bunch of embeded linux appliances that we will be installing at a few locations. Built the whole thing from scratch using Raspbian (debian based) and Raspberry Pis. There are ...
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39 views

Removed USB storage device is still mounted

I'm working on a embedded linux system based on busybox. Sometimes a USB device which is physically removed from the post is still displayed in mount, df or /proc/mounts. If I reattach the device, it ...
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1answer
47 views

How to get log from u-boot without com-port

U-boot is configured to print its logs into com-port by default. There is a device I can't receive this information (without uart/com). Can I configure u-boot to store its log strings into some place ...
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1answer
100 views

How can I boot with a compressed rootfs?

My problem is: I cannot use compressed rootfs (the kernel crashes during boot) but uncompressed ones work fine. What I did: I'm using Buildroot 2013.11 to generate Images for my embedded Linux ...
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74 views

using sf probe to make u-boot faster

My uboot was running slow on a ARM cortex A9 processor based Xilinx zynq chip. Xilinx forum referred me to the following to solve this issue: +From 0a212cfc2dd4e4d1595de2ca2dde3f642e5707e7 Mon ...
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2answers
69 views

Could not mount UBIFS on SD card

I guess this is not a big problem, still I can't see what's the matter. I'm building Images for an Embedded Linux (2.6.39) ARM9 System with Buildroot 2013.11, which is booting from an SD card. I was ...
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1answer
54 views

WARNING: at kernel/irq/handle.c - after changing rootfs, but why?

today I changed from an image with initramfs to an image with separate kernel and rootfs. Theses images are used for an Embedded System (ARM9 SAM9G25), that is runnging with an Linux 2.6.39. During ...