Linux stuff (old stuff)

In this page it is randomly collected information I have found useful in setting up the Linux operative system on various PCs and laptops, or in installing software therein. Some of this might be useful to you.
Find out informations about your operating system
Use of uname
Kernel compilation
Issues with Installation of Maple 9.5

  1. To find out informations about Linux release, kernel and architecture, use the following linux commands:
    • cat /etc/redhat-release
    • uname -r
    • rpm -q --queryformat "%{ARCH}\n" kernel
  2. Use of uname:
    • uname -a : display all information
    • uname -s : display operating system
    • uname -n : display name of the machine
    • uname -r : display operating system release
    • uname -v : display operating system version
    • uname -m : display machine type
    • uname -p : display processor type
  3. Compilation of a new Linux kernel
    Sometimes one needs to build and compile a new Linux kernel because a new, more stable version has been produced, or because a new version has been enriched with more functionality, or one need to recompile the present version simply to include variations to the configuration file. For example, I was forced to modify few parameters commanding wireless functionality in the configuration file, so to be able to use a wireless driver later. Thus, I was starting with the kernel 2.6.17-1.2174_FC5 and I needed to modify few parameters in the configuration file related to this kernel. First of all, the kernel and the configuration parameters are loaded at boot time from the /boot directory. For instance I had the following files for the /boot directory:
    • config-2.6.17-1.2174_FC5
    • initrd-2.6.17-1.2174_FC5.img
    • vmlinuz-2.6.17-1.2174_FC5
    The first file contains all parameters with which the kernel vmlinuz-2.6.17-1.2174_FC5 has been compiled. The second file is needed to start few devices before the kernel is loaded. I don't know exactly how works, but it is absolutely needed. To build and compile a kernel with added wireless functionality I have followed advice from a web page: The first thing to do is to download the desired kernel. In my case, I had nothing under /usr/src/redhat/BUILD, where the source for the kernel should be on my system (FEDORA CORE 5). It is, actually, not strictly necessary to build the kernel under "/"; given that, these days, lots of space is allocated to users under "/home/a_user" (where "a_user" is your user name), it is perhaps more convenient to build the kernel under the home directory. This what I have done for this built. Symbolic links to "/usr/src/linux", "/usr/src/redhat/", etc can always be added later. In order to create a tree to build the kernel under a home directory the package "fedora-rpmdevtools" has to be installed (and it could be useful for other things later). This could be done using the following command:
    yum install fedora-rpmdevtools
    From this package we are going to use the following command to build the tree:
    Having done this under "/home/james" I have now the following directory created: "/home/james/rpmbuild". Inside it other directories (composing the tree) are created: BUILD, RPMS, SOURCES, SPECS, SRPMS. These are going to contain all the stuff built during the process. Given that the kernel is going to be built under my home directory, I do not need to become root to do the actual building; only the installation will require root privileges.
    Let us proceed with downloading the SRC.RPM file. It should be exactly of the same type that is at present running on your machine. For example I downloaded the file kernel-2.6.17-1.2174_fc5.src.rpm on "/home/james/" from the fedora repository. This is a source RPM file. I could have downloaded a zipped tar file instead; things would have been pretty similar. I, then, did the following:
    1. install the kernel with command line:
      rpm -ivh kernel-2.6.17-1.2174_fc5.src.rpm
    2. extract the kernel and apply all the Fedora patches ("--target" should be changed according to the architecture used):
      rpmbuild -bp --target= i586 /home/james/rpmbuild/SPECS/kernel-2.6.spec
      This is, usually, called the "%prep stage" of the RPM build.
    After these two commands, the source directories will be properly located in:
    More specifically, we will use all files under the following subdirectory of /home/james/rpmbuild/BUILD/kernel-2.6.17, linux-2.6.17.i586, which we will call simply Linux, from now on. Now we cd the Linux directory:
    cd /home/james/rpmbuild/BUILD/kernel-2.6.17/linux-2.6.17.i586
    After this we want to make sure that all header or library files created while building up the last kernel are removed, so that the source directory is pristine. We do this using:
    make mrproper
    In the Linux directory you should find the configuration file, ".config", which comes with the SRC.RPM package. We better start with the configuration file previously used, otherwise we are going to loose all previous setup.
    Thus we,
    cp .config .config.old
    and use the present configuration file under /boot:
    cp /boot/config-2.6.17-1.2174_FC5 .config
    Before carrying on with the kernel configuration we vi Makefile and find the following initial lines:
    VERSION = 2
    SUBLEVEL = 17
    Well, all this information will be appended to the newly compiled kernel when the whole process is completed. Therefore, we need to change the last line with some unique name. In my case I did:
    EXTRAVERSION = -added_wireless_functionality
    Now we can proceed with the configuration. We use a graphical interface through the command:
    make xconfig
    A graphical interface is started where we can tick or un-tick options; this is how we modify the configuration for the new kernel. The kind of configuration is typically suggested in help files from modules we want to install, so there is no problem in doing that. At the end we save and exit: automatically a new .config is saved in place of the old one, which is lost. It is interesting to observe that even if no changings are required to ".config", it is still better to call, save and exit xconfig or, otherwise the bzImage compilation will not proceed.
    After the configuration we need a bit of cleaning:
    make clean
    and the compilation can start:
    make bzImage
    Then it is time for modules compilation:
    make modules
    Both compilations will take a while (even an hour or so). Now we are ready for installation. First we need to become root:
    Next, we type:
    make modules_install
    The freshly created modules will be copied under /lib/modules/2.6.17-added_wireless_functionality.
    To create the initrd file we do:
    mkinitrd /boot/initrd-2.6.17-added_wireless_functionality.img 2.6.17-added_wireless_functionality
    Essentially, if the kernel RPM source is, for instance, kernel-blabla.src.rpm, the command will be "mkinitrd /boot/[a name].img blabla". To conclude we copy the important files under /boot:
    cp /usr/src/redhat/BUILD/kernel-2.6.17/linux-2.6.17.i686/arch/i386/boot/bzImage /boot/bzImage-2.6.17-added_wireless_functionality
    cp /boot/
    cp /usr/src/redhat/BUILD/kernel-2.6.17/linux-2.6.17.i686/.config /boot/config-2.6.17-added_wireless_functionality
    Also, we need to include in the boot loader, GRUB, those lines related to the new kernel. The file to modify boot loader is /boot/grub/grub.conf Once grub.conf is modified, the new kernel will appear after rebooting.  Here is an example of the grub.conf file I use.
  4. Installation and configuration of driver for wireless card Intel/Pro 3945ABG
    As I was expecting when installing Linux Fedora Core 5 on my Dell Latitude D520 laptop, all wireless stuff did not work. The first thing to do was to check whether the driver for the related hardware, an Intel/Pro 3945ABG adapter, was already installed on the laptop; it wasn't, so I had, first to download and install it. I found the software as a tgz file, ipw3945-1.1.0.tgz. When I untarred this file there was an INSTALL text file saying that I had to install the latest ieee80211 subsystem. So I downloaded a ieee80211-1.2.15.tgz, unzipped/untarred, followed the instructions and installed it. Then started with ipw3945. In the instructions I also found that two other packages, a "microcode" and a regulatory deamon, had to be downloaded. Thus, I downloaded a ipw3945-ucode-1.13.tgz and a ipw3945d-1.7.22.tgz. Also I read that the kernel needed configuration with specific parameters. So I had to configure and build the kernel with what was suggested, before being actually able to install the ipw3945 driver.
    The installation started in the ipw3945 directory:
    cd /ipw3945-1.1.0
    Then it was time to install the firmware files (the "microcode"). This consisted of the following commands:
    tar xzvf ipw3945-ucode-1.13.tgz
    cp ipw3945-ucode-1.13/ipw3945.ucode /lib/firmware/.
    In order to work, the driver needs a "deamon". This is installed as follows:
    tar xzvf ipw3945d-1.7.22.tgz
    cp ipw3945d-1.7.22/x86/ipw3945d /sbin/.
    So the deamon is /sbin/ipw3945d. All the software is installed with the above instructions. This does not, however suffice to activate the driver. For achieving that the kernel has to load the ipw3945 module. In other words we could say that the wireless interface needs to be running, in order to make some use of the wireless card. We can do that using the modprobe mechanism. First,
    cp ipw3945.ko /lib/modules/2.6.17-added_wireless_functionality/.
    depmod -a
    The depmod -a is used to update the modules dependency in a general dependency tree. Then we have to add the following lines to file /etc/modprobe.conf:
    alias eth1 ipw3945
    install ipw3945 /sbin/modprobe --ignore-install ipw3945; sleep 0.5; /sbin/ipw3945d --quiet
    remove ipw3945 /sbin/ipw3945d --kill; /sbin/modprobe -r --ignore-remove ipw3945
    The first line identifies interface eth1 with the ipw3945 driver. The next two lines are the correct commands to load or unload the driver+regulatory deamon. Inclusion of these lines in modprobe.conf insures that the interface is automatically loaded at boot. But the regulatory deamon can automatically be loaded only with the inclusion in /etc/rc.local of the following line
    /sbin/ipw3945d --quiet
    Finally, we need to configure eth1 so that when the command ifup eth1 is typed, the computer is hatched to a wireless connection. Things here are really complicated, and they will vary according to the kind of wireless connection and encryption used. I use a WPA2-AES encription, with a certain passphrase that will pretend to be "my_passphrase". In order to handle WPA encryption a program called wpa_supplicant is needed. Luckily I had this program already installed as /usr/sbin/wpa_supplicant. The idea is to have this program running in background and coming to help when a network through eth1 is started. I found that the best way to act is as follows.  First create a file /etc/wpa_supplicant/wpa_jaldomaldo.conf ("jaldomaldo" is the SSID of my wireless network) with these lines:


    # Home network
    pairwise=CCMP TKIP
    group=CCMP TKIP

    Then remove eventual keys from /etc/sysconfig/network-scripts/keys-eth1. Also, the /etc/sysconfig/network-scripts/ifcfg-eth1 file will have to have the following content:

    # Please read /usr/share/doc/initscripts-*/sysconfig.txt # for the documentation of these parameters.

    To start the network one can follow different routes. I have written a very simple bash shell, "/etc/sysconfig/network-scripts/start-wireless", which has the following content:



    /usr/sbin/wpa_supplicant -Bw -i$DEVICE -c/etc/wpa_supplicant/wpa.conf -Dwext
    sleep 10.0
    /sbin/ifup $DEVICE

    The shell will have to be started as root in the following way:
    /etc/sysconfig/network-scripts/start-wireless eth1
    Basically I start the wpa_supplicant daemon in the background and then wait for a while (to give time to the wireless driver to associate to the wireless network) before bringing up the interface eth1.
    To bring down the wireless network I follow this method. In file /etc/sysconfig/network-scrpts/ifdown the following lines are written before the line "OTHERSCRIPTS...":

    # is the device wireless?
    is_wireless_device ${DEVICE} && . ./ifdown-wireless

    Then a new file /etc/sysconfig/network-scripts/ifdown-wireless is written like this:


    killall wpa_supplicant
    rm -rf /var/run/wpa_supplicant

    The wireless network is thus ended with:
    ifdown eth1
    As I said, one can imagine many methods for starting or ending the newtwork; I'm quite happy doing what I have just described.
  5. Issues with the installation of Maple 9.5
    The first time I have tried to install the Linux version of Maple 9.5 I had serious problems. I was installing from a CD, running the "installMapleLinuxSU" shell with the command:
    sh installMapleLinuxSU
    The result of this was a lot of complaining about few shared libraries missing. I looked up the internet and found that this sort of error messages are given by Java setting the LD_ASSUME_KERNEL environment variable to the wrong value. It does not help setting this variable to the correct value before running "installMapleLinuxSU", because this shell, ultimately, calls a binary file, "LinuxInstaller.bin", which has specific settings for LD_ASSUME_KERNEL; thus any previous setting by the user would be changed by the Linux installer. The only way, as suggested in the web, to avoid this is to comment, in "LinuxInstaller.bin" all lines containing "export LD_ASSUME_KERNEL=". Of course there is no way of doing this until the "LinuxInstaller.bin" file resides on a CD. So, the first thing I have done was to copy all CD's content under a temporary directory (for me /home/james/var). Then I could change the "LinuxInstaller.bin" file as needed. A word of caution is needed here, though. This file is a binary file. If it is edited in the normal way, with any editor or, even, with vi, things are changed in such a way that the binary lines will be messed up and the installation will, again, fail. The proper way to edit the file, commenting out the "export LD_ASSUME_KERNEL" lines, is by opening the file in this way:
    vim -b LinuxInstaller.bin
    Once the file is open the above mentioned lines will have to be commented as "#xport LD_ASSUME_KERNEL". In this way an ASCII character is replaced with another ASCII character, and the rest of the binary file is not compromised. After having done all this the Maple installer installed Maple OK.

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