Not sure if this is two question, but I wanted to start with both here in case they are related. I use a Linux PXE and grub for dos boot in various ways. I have used the same file system adding a few scripts here and there but mostly updating the kernel for new hardware. Starting with kernel 3.12.xxx and the latest 3.18 rc4 main line I am getting "oom_adj" deprecated and some wait_for_sysfs errors. My Linux skill level is somewhat basic out of ignorance mostly. I have goggled and learned a lot, so just because I use a term it does not mean I know what I am saying :-)
Background:
I started by remastering P.I.N.G from windowsdream. http://www.windowsdream.com/ping.html This is a cool ISO that will backup and restore hard drive images to a share. It's basically a big Pearl script that uses Linux commands to create shares, save partition, clear and make them back. So I started with that and made a intrd.gz file system. So I imagine a lot of my issues could be out of date lib's, my udev rules need to be updated, or my kernel make file (.config) is wrong. Also, sometimes, not always, my mouse USB will cycle though disconnects/re-connects. It seems to very from boot to boot. This boot may do it and the next boot will not. I will attache some screen shots and my .config file. BTW, P.I.N.G was based on Linux From Scratch (LFS).
Questions:
The open ended question is how to fix it?
Are the following questions related?
Is there setting in the .config to switch from oom_adj to oom_score_adj?
Is the /proc/2000 a lib issue?
Is the waiting_for_sysfs udev rules issues?
For the USB disconnecting/re-connecting, I read somewhere that Intel question something about some timing and some cheaper hardware may have pushed the spec a little. I can not find it any more. I did find something in the .config about using uHCI, but I saw somewhere about xHCI. I assume it has something to do with USB 2.0 vs USB 3.0, but I am not sure. Also, is this USB 1?
Any thoughts?
Looks like there are too many lines for the .config, I don't see how to attach it. If anyone wants to see it, let me know either how to post it or send it to them.
Related
I'm working an a system with embedded Linux (Kernel 2.6.31).
It is a AT91SAM9G20 chip inside, and some of the Pins are forwarded to the outside.
Now I want to use them as GPIO Inputs.
I read the gpio.txt documentation about using the GPIOs via filesystem, and that works very well 'til here. I connected some switches to the gpio-pins and I can see the result in /sys/class/gpio/gpioX/value. But now I'd like to react on a change without busy-waiting in a loop. (i.e echo "Switch1 was pressed").
I guess I need interrupts here, but I couldn't find out how to use them without writing my own kernel driver. I'm relatively new to Linux and C (I normally program in Java), so I'd like to handle the Interrupts via sysfs too. But my problem is, that there is no "edge"-file in my GPIO directory (I guess because this is only since Kernel version 2.6.33+). Is that right? Instead of "edge" I've got a uevent file in there, which is not described in gpio.txt.
In the gpio.txt documentation there was a Standard Kernel Driver mentioned: "gpio_keys". Is it possible to use this for my problem?
I guess it would be better to work with this driver than allowing a userspace program to manipulate kernel tasks.
I found a lot of codesnippets for writing my own driver, but I wasn't even able to find out which of the 600 gpio.h files to include, and how to refer to the library (cross compiler couldn't find the gpio.h file).
Sorry for newbie questions, I hope you could give me some advices.
Thanks in advance
See this for an example on how to do that. Basically, the thing you're missing is the usage of the select or poll system calls.
I have a linux busybox based system on a chip. I want to provide an update to users in the field and this requires updating some files in /lib /usr/bin and /etc. I don't think that it's safe to simple untar the files directly. Is there a safe way to do this including /lib files that may be in use?
Some things I strongly prefer in embedded systems:
a) Have the root file system be a ramdisk uncompressed from an image in flash. This is great because you can experimentally monkey around with it to your heart's content and if you mess up, all you need is a reboot to get back to the flashed configuration. When you have tested a set of change you like, you generate a new compressed root filesystem image and flash that.
b) Use a bootloader such as u-boot to do your updates - flashing a new complete image - rather than trying to change the linux system while it is running. Though since the flashed copy isn't live, you can actually flash it while running. If you flash a bad version, u-boot is still there to flash a good one.
c) Processors which have mask-rom UART (or even USB) bootloaders, making the system un-brickable - nothing more than a laptop and a serial cable or usb/serial converter is ever needed to do maintenance (ie, get a working u-boot image on the flash, which you then use to get a working linux kernel+compressed root fs image on it)
Ideally your flash device is big enough to partition into two complete filesystems and each update updates the other side (plus copying over config files if necessary) and updates the boot configuration to boot from the updated side.
Less ideal is to update in-place but have some means of detecting boot failure (watchdog that's not touched until after boot, for example) and have a smaller, fallback partition which is capable of accepting another update and fixing the primary partition.
As far as the in-place update of a live filesystem, just use a real installer (which will move the target files out of the way before replacing them to avoid the problem you describe).
You received two excellent answers above and I Strongly encourage you to do what you were advised to.
There is, however, a more simple way. In a matter of fact you can just untar your libraries, provided that the process that does this is statically linked.
I recently read a post (admittedly its a few years old) and it was advice for fast number-crunching program:
"Use something like Gentoo Linux with 64 bit processors as you can compile it natively as you install. This will allow you to get the maximum punch out of the machine as you can strip the kernel right down to only what you need."
can anyone elaborate on what they mean by stripping down the kernel? Also, as this post was about 6 years old, which current version of Linux would be best for this (to aid my google searches)?
There is some truth in the statement, as well as something somewhat nonsensical.
You do not spend resources on processes you are not running. So as a first instance I would try minimise the number of processes running. For that we quite enjoy Ubuntu server iso images at work -- if you install from those, log in and run ps or pstree you see a thing of beauty: six or seven processes. Nothing more. That is good.
That the kernel is big (in terms of source size or installation) does not matter per se. Many of this size stems from drivers you may not be using anyway. And the same rule applies again: what you do not run does not compete for resources.
So think about a headless server, stripped down -- rather than your average desktop installation with more than a screenful of processes trying to make the life of a desktop user easier.
You can create a custom linux kernel for any distribution.
Start by going to kernel.org and downloading the latest source. Then choose your configuration interface (you have the choice of console text, 'config', ncurses style 'menuconfig', KDE style 'xconfig' and GNOME style 'gconfig' these days) and execute ./make whateverconfig. After choosing all the options, type make to create your kernel. Then make modules to compile all the selected modules for this kernel. Then, make install will copy the files to your /boot directory, and make modules_install, copies the modules. Next, go to /boot and use mkinitrd to create the ram disk needed to boot properly, if needed. Then you'll add the kernel to your GRUB menu.lst, by editing menu.lst and copying the latest entry and adding a similar one pointing to the new kernel version.
Of course, that's a basic overview and you should probably search for 'linux kernel compile' to find more detailed info. Selecting the necessary kernel modules and options takes a bit of experience - if you choose the wrong options, the kernel might not be bootable and you'll have to start over, which is a pain because selecting the options and compiling the kernel can take 15-30 minutes.
Ultimately, it isn't going to make a large difference to compile a stripped-down custom kernel unless your given task is very, very performance sensitive. It makes sense to remove things you're never going to use from the kernel, though, like say ISDN support.
I'd have to say this question is more suited to SuperUser.com, by the way, as it's not quite about programming.
I have a problem probably with my arm toolchain but maybe there's something other that I do wrong. I have Chinese made dev board qq2440 using Samsung s3c2440 ARM9 uC. I'm using Ubuntu x86 with native gcc(4.3.3) and cross-compile version arm-unknown-linux-uclibc-gcc (crosstool-NG-1.3.2) 4.3.2
I followed tutorials from http://blog.leshak.ru/english/pages/how-to-install-u-boot-linux-2629-rootfsjffs2-busybox-1132-into-nand-qq2440/
and used Leshak's kernel patches for that board. Problem is that his binaries work perfectly and mine don't...
I communicate with my board over RS232 (serial port) and I have serial terminal configured on target Linux. I use Leshak's uboot image. To configure my kernel I use following command line:
qq2440> setenv bootargs 'noinitrd root=/dev/mtdblock2 rootfstype=jffs2 rw console=ttySAC0,115200'
For target I use vanilla Linux sources version 2.6.29, with patches created by Leshak. I don't honestly believe that this will ever be supported officially by Linux as it's not mainstream product.
My kernel image starts booting up, but it probably changes bandwidth (or CPU frequency) to some non standard value (tried all standard ones already). Instead of dots indicating loading kernel into memory I've got only trash instead. Unfortunately it doesn't probably finish the boot process as the network interface nor file system don't come up. So I figured out that it panics somewhere in the middle.
Any ideas what should I do next?
Thanks & regards,
Chris
There are a lot of different things that could be going on here.
It sounds like you are talking about a serial port, and that it appears to be giving garbage once control is passed to the kernel from uboot. Am I understanding that correctly?
Look into specifying the baud rate, parity, etc. for the serial console on the kernel commandline.
Oh, and IIRC, there was some 'early_printk' thing in the ARM Linux tree that might help you debug serial console problems. (But I'll warn you -- it's been a couple years since I dealt with that so my memory is fuzzy.)
Double-check that the memory address layout (the locations of all the various devices) matches what your board has. (I think this is probably not the issue, but wanted to mention it for completeness.)
You say that you have a binary kernel that works correctly; compare the kernel config of that kernel to the config you are using for building your kernel. Investigate every difference, particularly any specific to ARM.
You may want to double-check the endianness of your toolchain vs what your board is expecting. Some of the ARM / XScale processors can be configured to big-endian or little-endian in software, so it might be worth double-checking.
Just enable the debug build of the kernel[while building the uImage] so that you get a more clearer picture of the scenario [Just would make your boot up somewhat slow since all the printk's would be enabled].
Can you check whether you are passing the correct parameters to the UART ie. Serial Port Name, it's baud rate etc This would be provided by the board manufacturer-Samsung
WRT the network instead of DHCP can you just assign a static ip address to your system as it might be possible that the DHCP process is still not ON.
Also a better option would be to use NFS but yeah, it depends on your choice and the purpose of your application. To use NFS, your network should be UP & running and your filesystem should be shared.
As retracile has already pointed out "Endianness" could be a point to look into !!!
You can refer this link which might help you out since it is specific to S3C2440
Hope this helps.
-hjsblogger
I had a similar problem at one point when I omitted --send-cmd from picocom. this is the command I issue to picocom for serial uBoot comms with the mini2440.
picocom -b 115200 /dev/ttyS0 --send-cmd "sx -vv"
Can anyone point me to a good tutorial on creating a bootable Linux CD from scratch?
I need help with a fairly specialized problem: my firm sells an expansion card that requires custom firmware. Currently we use an extremely old live CD image of RH7.2 that we update with current firmware. Manufacturing puts the cards in a machine, boots off the CD, the CD writes the firmware, they power off and pull the cards. Because of this cycle, it's essential that the CD boot and shut down as quickly as possible.
The problem is that with the next generation of cards, I have to update the CD to a 2.6 kernel. It's easy enough to acquire a pre-existing live CD - but those all are designed for showing off Linux on the desktop - which means they take forever to boot.
Can anyone fix me up with a current How-To?
Update:
So, just as a final update for anyone reading this later - the tool I ended up using was "livecd-creator".
My reason for choosing this tool was that it is available for RedHat-based distributions like CentOs, Fedora and RHEL - which are all distributions that my company supports already. In addition, while the project is very poorly documented it is extremely customizable. I was able to create a minimal LiveCD and edit the boot sequence so that it booted directly into the firmware updater instead of a bash shell.
The whole job would have only taken an hour or two if there had been a README explaining the configuration file!
There are a couple of interesting projects you could look into.
But first: does it have to be a CD-ROM? That's probably the slowest possible storage (well, apart from tape, maybe) you could use. What about a fast USB stick or a an IEE1394 hard-disk or maybe even an eSATA hard-disk?
Okay, there are several Live-CDs that are designed to be very small, in order to e.g. fit on a business card sized CD. Some were also designed to be booted from a USB stick, back when that meant 64-128 MiByte: Damn Small Linux is one of the best known ones, however it uses a 2.4 kernel. There is a sister project called Damn Small Linux - Not, which has a 2.6 kernel (although it seems it hasn't been updated in years).
Another project worth noting is grml, a Live-CD for system administration tasks. It does not boot into a graphic environment, and is therefore quite fast; however, it still contains about 2 GiByte of software compressed onto a CD-ROM. But it also has a smaller flavor, aptly named grml-small, which only contains about 200 MiByte of software compressed into 60 MiByte.
Then there is Morphix, which is a Live-CD builder toolkit based on Knoppix. ("Morphable Knoppix"!) Morphix is basically a tool to build your own special purpose Live-CD.
The last thing I want to mention is MachBoot. MachBoot is a super-fast Live-CD. It uses various techniques to massively speed up the boot process. I believe they even trace the order in which blocks are accessed during booting and then remaster the ISO so that those blocks are laid out contiguously on the medium. Their current record is less than 6 seconds to boot into a full graphical desktop environment. However, this also seems to be stale.
One key piece of advice I can give is that most LiveCDs use a compressed filesystem called squashfs to cram as much data on the CD as possible. Since you don't need compression, you could run the mksquashfs step (present in most tutorials) with -noDataCompression and -noFragmentCompression to save on decompression time. You may even be able to drop the squashfs approach entirely, but this would require some restructuring. This may actually be slower depending on your CD-ROM read speed vs. CPU speed, but it's worth looking into.
This Ubuntu tutorial was effective enough for me to build a LiveCD based on 8.04. It may be useful for getting the feel of how a LiveCD is composed, but I would probably not recommend using an Ubuntu LiveCD.
If at all possible, find a minimal LiveCD and build up with only minimal stripping out, rather than stripping down a huge LiveCD like Ubuntu. There are some situations in which the smaller distros are using smaller/faster alternatives rather than just leaving something out. If you want to get seriously hardcore, you could look at Linux From Scratch, and include only what you want, but that's probably more time than you want to spend.
Creating Your Own Custom Ubuntu 7.10 Or Linux Mint 4.0 Live-CD With Remastersys
Depends on your distro. Here's a good article you can check out from LWN.net
There is a book I used which covers a lot of distros, though it does not cover creating a flash-bootable image. The book is Live Linux(R) CDs: Building and Customizing Bootables. You can use it with supplemental information from your distro of choice.
So, just as a final update for anyone reading this later - the tool I ended up using was "livecd-creator".
My reason for choosing this tool was that it is available for RedHat-based distributions like CentOs, Fedora and RHEL - which are all distributions that my company supports already. In addition, while the project is very poorly documented it is extremely customizable. I was able to create a minimal LiveCD and edit the boot sequence so that it booted directly into the firmware updater instead of a bash shell.
The whole job would have only taken an hour or two if there had been a README explaining the configuration file!
Debian Live provides the best tools for building a Linux Live CD. Webconverger uses Debian Live for example.
It's very easy to use.
sudo apt-get install live-helper # from Debian unstable, which should work fine from Ubuntu
lh_config # edit config/* to your liking
sudo lh_build