[linuxkernelnewbies] Fedora Core 11 Setup for Digital Signal Processing

[Peter Teoh]

http://galois.digitalsignallabs.com/notes.htm   Contents 1  Introduction 2  Notes 2.1  Configuration >From A Fresh Install of Fedora Core 11 2.2  dhcpd 2.3  Subversion Access Via Apache 2.4  Broadcom (Laptop) Wireless Card Configuration 2.5  Netgear Wireless Card Configuration 2.6  Airlink 101 RALINK-Based Wireless Card Configuration 2.7  Ghostscript 2.8  Development Versions of GNU-Octave and GNUPlot 2.9  Dynamic DNS Setup 3  Tips and Tricks 3.1  Bug Tips 3.2  Kernel Module Tips 3.3  Emacs/XEmacs Tricks 3.4  Video Tricks 3.5  yum/rpm Tricks 3.6  ssh Tricks 3.7  Networking Tricks 3.8  CD/DVD Media Tricks 3.9  Services Tricks 3.10  Screensaver Tricks 3.11  Linux Tricks 3.12  acroread Tricks and Gnome Mechanisms 3.12.1  GTK Engine Warnings 3.12.2  Secondary Dependency Mechanism 3.13  Firefox Tricks 3.14  Disk and File System Tricks 3.15  Tricks to get DVDs to Play 3.16  Hardware Tricks 3.17  Sound Tricks 3.18  Printer (CUPS) Tricks 3.19  Linker Tricks 3.20  LATEX Tricks 3.21  Router Tricks 4  Todo 8pt 0pt 1  Introduction This is a record of system administration notes and tricks for administering my Fedora Core system. The Notes section currently documents what I’ve had to do in upgrading from a stable, configured Fedora Core 6 system to a fresh install of Fedora (Core) 8 (Fedora Unity respin 20080204, to be exact) in order to reconfigure the system back to a working, usable linux system. Tricks for various applications or topics are under the Tricks section. More major pieces of work (e.g., custom-building xemacs) are documented in the appendices. Note that some of these steps may reference scripts or other files that will be in the linuxadmin/misc directory. Note that the current version of the document was updated when converting from F10 to F11. 2  Notes 2.1  Configuration >From A Fresh Install of Fedora Core 11 yum update swap ctrl key with capslock via System/Preferences/Hardware/Keyboard install emacs yum install xemacs Modify gnus for desired signature delimiter: cd ${LA_PATH}misc/emacs make -f message.mak make -f message.mak cleaninstall make -f message.mak install yum install zile configure /etc/ssh/sshdc_config to use an alternate port /sbin/service sshd restart chmod -R 700 ~/.ssh add <username> to /etc/sudoers remove Documents, Music, etc. subdirectories in home directory. configure svn yum install svn create user svn, being sure to specify userid of 501 and groupid of 501 (to match existing file system). Note that the system-config-user GUI was not able to correctly add the svn user because su svn would fail with no such user, while the svn user was clearly present in the GUI. Instead the adduser and groupadd commands (to add the svn group before the svn user was added) had to be used. add svnserve script to /etc/rc.d/init.d directory and make symbolic link S98svnserve in /etc/rc.d/rc5.d to it. yum install xchat restore repository working copies edit /etc/fstab and add the line: /dev/sdb1 /svnserver ext3 defaults 1 2 svn co svn://localhost/svnserver/svn/<username> /home/<username> svn co svn://localhost/svnserver/svn/digitalsignallabs /home/digitalsignallabs svn co svn://localhost/svnserver/svn/linuxadmin /home/linuxadmin etc. yum install gkrellm rearrange gnome panels yum install pygpgme yum install gconf-editor Hide desktop items Trash, etc., by editing the /apps/nautilus/desktop/ entries using gconf-editor Configure keyboard shortcuts yum install audacious yum install hg yum install emacs install Adobe products yum install adobe-release rpm -ivh http://linuxdownload.adobe.com/adobe-release/adobe-release-i386-1.0-1.noarch.rpm yum install AdobeReader_enu Install Adobe’s 32-bit flash player plugin or download Adobe’s alpha 64-bit version as described here: https://fedoraproject.org/wiki/Flash, and test here: http://www.adobe.com/shockwave/welcome/. Note that this only installs “Flash Player” (which is apparently what Mozilla calls “Shockwave Flash”) and not “Shockwave Player.” install rpmfusion repositories yum install rpmfusion-free-release yum install rpmfusion-nonfree-release install postgresql server, clients, and data yum install postgresql yum install postgresql-libs yum install postgresql-server generate the server cluster and start it running: as root, /sbin/service postgresql initdb /sbin/service postgresql start /sbin/chkconfig postgresql on edit /var/lib/pgsql/data/pg_hba.conf and set like in $LINUXADMINHOME/misc/postgresql/pg_hba.conf (especially see the access configurations at the end, and edit /var/lib/pgsql/data/postgresql.conf to be like $LINUXADMINHOME/misc/postgresql/postgresql.conf, especially the listen_address setting. Without the latter, the postgresql server will not accept connections over the tcpip network but just over localhost. Recreate the database data (database schemas, tables, data, etc.): cd /home/<username>/local/data;cat firstflight.dmp | psql and etc. (as user postgres) install pgadmin3 client yum install pgadmin3 yum install pgadmin3-docs yum install mail-notification yum install wireshark-gnome Install the nvidia graphics card driver. nvidia has changed their driver organization based on different families. The GeForce FS5200 family is obtained with yum install kmod-nvidia-173xx. reboot get the eye-candy compiz stuff installed yum install compiz yum install compiz-fusion yum install compiz-fusion-extras yum install compiz-manager yum install compiz-gnome yum install gnome-compiz-manager-devel. Note: without this, the “window focus follows mouse” stopped working. to disable the pc speaker from beeping, pop up the ALSA mixer and mute the pc speaker channel. install other web browsers for variety: yum install epiphany. Wanted another browser on-hand. yum install seamonkey yum install mathml-fonts wanted a dictionary so I tried yum install stardict yum install octave yum install octave-forge make /backup directory on / and copy backup files NOTE: ensure there are at least two copies on each system. setup crontab from $LINUXADMINHOME/misc/crontab.txt cp $LINUXADMINHOME/applications/keychain/keychain /usr/bin/. chmod a+x /usr/bin/keychain add /usr/bin/keychain to bash_profile add virtual box: yum install gt yum install yum localinstall $LINUXADMINHOME/applications/virtualbox/VirtualBox-1.5.6_28266_fedora8-1.x86_64.rpm yum install bodhi-client install codec set yum install gstreamer-plugins-good yum install gstreamer-plugins-bad yum install gstreamer-plugins-ugly yum install xine yum install gsview yum install vnc yum install pdfedit (for editing pdf forms) Configure for sensor data: yum install gnome-applet-sensors /usr/sbin/sensors-detect and accept defaults. This creates an lm_sensors service that provides the information to gnome-applet-sensors. add gnome-applet-sensors to a gnome panel yum install licq (an ICQ client) build and install jpeg2ps (for creating eps files from jpgs for generating pdf files from scans) at $LINUXADMINHOME/applications/jpeg2ps build and install the looktex utility (for looking up LaTeX bibliography entries) to a PATH location from $LINUXADMINHOME/applications/looktex ssh-agent operates by storing dynamic information in environment variables SSH_AUTH_SOCK. It is invoked initially (for an interactive GUI login session) by the /etc/X11/xinit/Xsession script. However, this only works for the subprocesses under the gdm session. In order to setup ssh-agent correctly for cron jobs, the ssh-agent socket information is captured in $HOME/.ssh/agent-info by the line in .bash_profile: umask 077; printf 'SSH\_AUTH\_SOCK=\%q\nSSH\_AGENT\_PID=\%q\nexport SSH\_AUTH\_SOCK SSH\_AGENT\_PID\n' "$SSH\_AUTH\_SOCK" "$SSH\_AGENT\_PID" > $AGENT\_FILE ) Then this info must be sourced at the beginning of the cron job with .  /.ssh/agent-info;<cron program>. yum install dia 2.2  dhcpd yum install dhcpd (the Internet System Consortium version 3.0.6) cp $LINUXADMINHOME/misc/dhcpd/dhcpd.conf /etc/. /sbin/chkconfig dhcpd on run system-config-network on the system hosting dhcpd, turn off dhcp, and establish static IP address 192.168.1.100 and DNSs 4.2.2.4 and 4.2.2.5. 2.3  Subversion Access Via Apache yum install mod_dav_svn edit /etc/httpd/conf/http to add the lines in $LINUXADMINHOME/misc/httpd/httpd-svn.conf htpasswd -bc /etc/dsp-auth-file <username> <passwd> htpasswd -bc /etc/btscdecoder-auth-file <username> <passwd> htpasswd -bc /etc/doc-auth-file <username> <passwd> htpasswd -bc /etc/edu-auth-file <username> <passwd> htpasswd -bc /etc/digitalsignallabs-auth-file <username> <passwd> htpasswd -bc /etc/archive-auth-file <username> <passwd> htpasswd -bc /etc/<username>-auth-file <username> <passwd> 2.4  Broadcom (Laptop) Wireless Card Configuration See instructions here: http://linuxwireless.org/en/users/Drivers/b43#firmwareinstallation As root: wget http://mirror2.openwrt.org/sources/broadcom-wl-4.150.10.5.tar.bz2 tar xjf broadcom-wl-4.150.10.5.tar.bz2 cd broadcom-wl-4.150.10.5/driver b43-fwcutter -w /lib/firmware wl_apsta_mimo.o 2.5  Netgear Wireless Card Configuration Note that the following procedure is embedded into the $LINUXADMINHOME/misc/netgear/netgear service script. install the netgear service: cp $LINUXADMINHOME/misc/netgear/netgear /etc/rc.d/init.d /sbin/chkconfig --add netgear download and install ndiswrapper: obtain ndiswrapper from unknown tar -xf ndiswrapper-version make make install ls /lib/modules/‘uname -r‘/build and verify at least the include directory and .config file is available. “install” the 64-bit driver to ndiswrapper: /usr/sbin/ndiswrapper -i $LINUXADMINHOME/misc/netgear/mrv8335x64.inf install the module and bring up the interface /sbin/modprobe -r ndiswrapper /sbin/modprobe ndiswrapper /sbin/iwconfig wlan0 channel 11 essid Euler key [1] <key-val> /sbin/ifconfig eth0 down /sbin/ifconfig wlan0 up /sbin/dhclient wlan0 2.6  Airlink 101 RALINK-Based Wireless Card Configuration To get an Airlink 101 AWLH670 wireles 802.11N network card working, do the following: Install the driver: yum install akmod-rt2860. Note that the 2860 includes drivers for the 2760 chipset. ln -s /etc/wpa_supplicant/wpa_supplicant.conf /home/linuxadmin/misc/airlink/wpa_supplicant.conf. ln -s /etc/sysconfig/wpa_supplicant /home/linuxadmin/misc/airlink/wpa_supplicant. ln -s /etc/sysconfig/network-scripts/ifcfg-wlan0 /home/linuxadmin/misc/airlink/ifcfg-wlan0. /sbin/service NetworkManager stop /sbin/chkconfig NetworkManager off /sbin/service wpa_supplicant restart /sbin/chkconfig wpa_supplicant on /sbin/service network restart /sbin/chkconfig network on Note that you may also want to change the ONBOOT option of the ifcfg-eth0 to no as well. 2.7  Ghostscript Version 8.63 of gs (ghostscript) from the fedora repo began crashing (actually from within ps2pdf14) when converting a latex file to pdf. download and build the latest version from ghostscript: svn co http://svn.ghostscript.com/ghostscript/trunk/gs gs 2.8  Development Versions of GNU-Octave and GNUPlot In order to get the “tikz” device option in the octave print() command, do the following: Obtain and build the development version of gnuplot (currently 4.5 patch 0): Go to the gnuplot site and download the development version via CVS. Install lua-devel package (via yum). ./prepare ./configure --with-lua make make install (Note: make install-strip didn’t work right) The make install utility doesn’t properly install the special style file, so manually cp --parents <rootinstall>/gnuplot/share/LaTeX/gnuplot-lua-tikz.sty /usr/local/texlive/2008/texmf/tex/latex/gnuplot-lua-tikz/.. Then update the TEX database with texhash. Obtain and build a patched version of octave: Download octave via hg (see octave’s web site for specific hg instructions). Apply patch: hg import --config patch.eol=lf --exact $LINUXADMINHOME/misc/octave-patch/changeset.patch ./autogen.sh ./configure make make install 2.9  Dynamic DNS Setup Register a dynamic DNS domain digitalsignallabs.dyndns.org with dyndns.org Have ISP create a cname record that points to the dynamic DNS domain address. Install a dynamic DNS update client. I chose ddclient. See http://www.dyndns.com/services/dns/dyndns/howto.html. 3  Tips and Tricks 3.1  Bug Tips https://fedoraproject.org/wiki/Bugs_and_feature_requests https://bugzilla.redhat.com/ 3.2  Kernel Module Tips Many (all?) drivers are installed as kernel modules. Kernel modules are manipulated using modprob, lsmod, and rmmod. Kernel module blacklists are lists of modules that the kernel should avoid loading. They are maintained in the path etc/modprobe.d/. 3.3  Emacs/XEmacs Tricks C-x describe-installation describes build-time information such as the ./configure options and other information. M-x gnuserv to make an instance of xemacs a gnu server. Then gnuclient to run a client. C-x # to quit editing a gnuclient frame. to select all text in a buffer, C-x h, to copy the selected text into the paste buffer, M-w. normal-mode rescans the current buffer and reloads the appropriate major mode. major-mode is a variable with the major mode named. It is useful, e.g., for determining the mode name to use for mode hooks. C-h v major-mode RET is a way to check it. to reestablish the tab key as tabs, (local-set-key [(tab)] ’self-insert-command). to select everything between the last point the cursor was at before a search and the current point, C-x C-x. to select everything in the entire buffer, C-x h. to toggle line wrapping, toggle-truncate-lines. to search/replace without retyping the search/replace strings from a previous search, use C-p (previous) to recall the previous search/replace strings, to get the output of a lisp command to go into the current buffer rather than the minibuffer, prefix with C-u. to set a “bookmark” at the current point in a buffer: C-x r SPC <register number>. To jump to a bookmark, C-x r j <register number>. C-h a runs apropos-command, which only searches the interactive functions. Use apropos to search all functions. to reload a buffer with current file contents, revert-buffer. 3.4  Video Tricks desktop-effects can be run from the command line. glxinfo gives glx info. Specifically, grep for “direct” to check if direct rendering is enabled. The “nouveau” driver is an open-source driver for the nvidia video cards and is the default installed with FC11. The “kmod-nvidia” driver is nvidia’s kernel module driver for nvidia video cards. vesa is another xorg (?) driver that can be useful for laptops but is not generally recommended. Here is a short summary of the video driver situation as of F11 beta: NVIDIA has provided good, albeit closed-source drivers (nvidia) all along so their stuff has worked well for years. ATI had provided poor closed-source drivers (fglrx) in the past so their stuff didn’t work so well. Now, as of F11, an upgraded/new ati foss driver (ati) is available that works well. 3.5  yum/rpm Tricks yum info xyz gives info on xyz. rpm -ql packagename lists the path/files that the package provides/installed. You can see and extract specific files in an rpm using file-roller. You can find out what package provided a file (e.g., an executable) by rpm -qf <filename>. To pull the rpm from a repo and place it in a local directory, first yum install yum-utils then yumdownloader <pkgname. To fake yum into thinking a package is available (e.g., when an alternate version has been manually installed), use the command rpm -ivh --justdb <pkgname>. 3.6  ssh Tricks I am using OpenSSH version OpenSSH_4.7p1, OpenSSL 0.9.8b 04 May 2006. I am using public key authentication. There are four important files for host/user in the /home/user/.ssh directory: id_rsa—The private key for host/user id_rsa.pub—The public key for host/user authorized_keys—A file of public keys from otherhosts/otherusers (simply concatenated together) that is used by sshd to determine which otherhosts/otherusers are allowed access to host/user. known_hosts—A file of remotehost<–>remoteuser public key associations. This file is used by the ssh client when host/user connects to a remotehost/remoteuser. The sshd on the remotehost/remoteuser provides the remotehost/remoteuser public key, and the ssh client checks that public key against the known_hosts public key for that host. If it is different, then it is possible that a “man-in-the-middle” attack is being attempted and the host/user may choose to abort. If StrictHostKeyChecking in ssh_config is on, then the user is forced to abort. The permissions of this directory and these files must be set to 700. To generate a public key / private key pair, use the command ssh-keygen with no options. This will by default generate an RSA key pair. ssh-agent is a daemon that allows a user on the local system to authenticate passphrases for ssh and scp. Such an authentication is called a key and ssh-agent is said to provide a “key ring.” A key is authenticated and added to the keyring using ssh-add. ssh and scp then search ssh-agent for the passphrase key when they are invoked and, if found, automatically authenticate the session. The communication between ssh-agent and ssh-add, ssh, and scp occur through sockets that are defined through environment variables. Each instantiation of ssh-agent (there only needs to be one, but there may be many in some cases) uses a different socket, thus the variables are defined for a specific instantiation. Further, simply invoking ssh-agent does not define these variables. One must do something like create a subshell, ssh-agent bash, or save the variables off via the -s option and source them into the process that requires the authentications. 3.7  Networking Tricks system-config-network starts the GUI network configuration application. /sbin/arp -a reports the IP to MAC address table for the local network. If an address isn’t there, ping it. two good, public DNSs are 4.2.2.4 and 4.2.2.5. nmap is a 3rd-party application that can be used to probe the local network for devices, e.g., nmap -sP x.y.z.0/24. ethtool lets you check the capabilities of your network device, such as ethernet speed. 3.8  CD/DVD Media Tricks cdrdao will read and write cd audio in “disk at once” (DAO) mode, which preserves inter-track mute intervals and is generally the closest way to clone a CD. to scan the computer (SCSI?) “bus”, cdrdao scanbus (as root). Note especially the comma-separated triplet at the beginning of the last line, e.g., “2,0,0” in 2,0,0 : Memorex , 16X-DDL-IN , 1.A3. This is used in the --device option in the read stage. http://cdrdao.sourceforge.net/drives.html#dt shows the “driver tables” indicating which --driver option to use in the read stage. Use the information from scanbus to locate the appropriate driver. Note that Memorex 16X-DDL-IN was not found there, but apparently the generic-mmc driver works. to read, cdrdao read-cd --datafile disk.bin --device 2,0,0 --driver generic-mmc disk.toc to write, cdrdao write --datafile disk.bin --device 2,0,0 --driver generic-mmc disk.toc dd if=inpfilename.ext of=outfilename.iso will create lovely iso images of data cds and data dvds, but only works in the read direction, i.e., you cannot use it to write an iso image file to a DVD or CD. apparently dd will not read audio cds. wodim image.iso will write an iso to DVD or CD. created flacrip (see /home/<username>/bin/flacrip) based on icedax and flac to automatically generate flac files from an audio cd. looks up song names in cddb database too. 3.9  Services Tricks A linux service is a script provided in /etc/rc.d/init.d that adheres to certain rules. The service can be started, stopped, restarted using /sbin/service servicename start | stop | restart. The service can be automatically placed in the various run-levels using /sbin/chkconfig --add servicename. In order to use the service with chkconfig, certain rules should be followed: The /etc/init.d/functions script should be sourced and certain functions there used for formatting nice output (like success and failure for the [OK] and [FAIL] indications). The file should have a comment header that follows certain formatting rules (the comments aren’t just comments!). For example, see the chkconfig, description, and processname lines in representative scripts. 3.10  Screensaver Tricks The actual screensaver executables are at /usr/share/applications/screensavers. 3.11  Linux Tricks man hier gives information on the file hierarchy of the typical linux system. ldd examines link information of an executable. objdum examines object file information. 3.12  acroread Tricks and Gnome Mechanisms For several Fedora versions (at least Fedora 8, Fedora 10, and Fedora 11), invoking Adobe Acrobat reader (acroread) could cause errors like Gtk-Message: Failed to load module "canberra-gtk-module": libcanberra-gtk-module.so: cannot open shared object file: No such file or directory and a similar message for libgnomebreakpad. Also messages like Gtk-WARNING **: Unable to locate theme engine in module_path: "clearlooks" can occur. The basic problem arises because the package for acroread doesn’t have its dependencies set up correctly, and it is a 32-bit application being run (in my case) under a 64-bit operating system. Therefore there are several i586 versions of libraries it requires which may already exist in the x86-64 versions, thus confusing the system maintainer into thinking the dependencies are already provided when in fact they are not. There is also a secondary mechanism for loading libraries when the application starts that is separate from the standard shared library mechanism implemented via ld-linux.so. This makes it more difficult to track down the causes of these messages. 3.12.1  GTK Engine Warnings The message Gtk-WARNING **: Unable to locate theme engine in module_path: "clearlooks" occurs because the i586 version of the GTK engines package isn’t installed. To fix, yum install gtk2-engines.i586. Clearlooks is one of the standard engines in this package; some of the other engines are package separately. 3.12.2  Secondary Dependency Mechanism The message \fn{Gtk-Message: Failed to load module "canberra-gtk-module": libcanberra-gtk-module.so: cannot open shared object file: No such file or directory} can occur when a GTK-based application is loaded and run. However, performing an ldd program1 will not reveal a dependency on the breakpad library. So precisly how is this breakpad library dependency coming about? The Gnome session runs a gnome_settings_daemon on startup which reads the gconf “registry” entries in /apps/gnome_settings_daemon/gtk-modules/ and loads them into the XSETTINGS protocol. Then when a GTK-based application is run, GTK queries XSETTINGS for a list of modules to load and loads them. Thus these types of dependencies arise via this mechanism and the entries in the /apps/gnome_settings_daemon/gtk-modules/ gconf key. Also note that breakpad is a component of bug-buddy—the facility for automating the reporting of Gnome bugs. You can remove the breakpad dependency by yum remove bug-buddy, or by simply unchecking the option in the gconf key /apps/gnome_settings_daemon/gtk-modules/. Alternately, you can satisfy the dependency by installing the i586 version of bug-buddy. 3.13  Firefox Tricks typing about:plugins in the address bar lists all plugins. to see the extensions that are configured, see tools -> addons -> extensions 3.14  Disk and File System Tricks A file system check similar to Window’s chkdsk can be performed as follows: unmount the volume to be checked: umount /mountpoint run the file check utility: /sbin/e2fsck -fv /dev/sd{a|b|c|...}{1|2|3|...} Format a drive with mkfs. You can create various types of filesystems with the -t type option. Logical Volumes. physical volume A physical drive or partition, such as /dev/sda1. Use pvdisplay to show physical volume / volume group mappings. volume group A group of one or more physical drives bound together into a single logical volume group. Use vgdisplay to display volume groups. logical volume A logical partition from a volume group. Use lvdisplay to display logical volumes and their associated volume groups and /dev paths. Then these /dev paths can be mounted just as a physical volume/partition (provided they’re not already mounted). 3.15  Tricks to get DVDs to Play Using xine, ensure all the following are installed: xine-lib libdvdcss xine-lib-arts xine-lib-extras xine-lib-extras-nonfree libdvdread libdvdnav 3.16  Hardware Tricks lspci lists pci bus components. dmidecode get BIOS and other motherboard information lshw is a handy third-party utility that lists hardware components (CPU, memory, etc.). The list of hardware generated by the installer is at http://smolts.org and is indexed by /etc/sysconfig/hw-uuid. It can be regenerated by smoltSendProfile -a. 3.17  Sound Tricks When some sounds failed to play (i.e., the play command) while others work fine, it could be that the pulseaudio daemon wasn’t started correctly for the user. This can happen if the /tmp/pulse-USER directory doesn’t have USER ownership or drwx permissions. 3.18  Printer (CUPS) Tricks To access the CUPS administration system, http://localhost:631/admin. 3.19  Linker Tricks Use /sbin/ldconfig path to set a new shared library path. Use ldd program to show the shared libraries used by the program and the paths the system is using for them. A good reference on shared libraries: http://www.dwheeler.com/program-library/Program-Library-HOWTO/x36.html. 3.20  LATEX Tricks Here’s the procedure to install a new set of fonts, namely kpfonts: Find the TEX local tree using the command kpsewhich -expand-var "$TEXMFLOCAL". Under Fedora 10 this was /usr/local/share/texmf. Extract the kpfonts archive’s texmf path to the path in the previous step. As root, run texhash. As root, run updmap-sys --enable Map=kpfonts.map. 3.21  Router Tricks The default DLink 655 router address is 192.168.0.1 but i changed it to 192.168.1.1. The cable modem address from the internal network is 192.168.100.1. The protocol between the router’s WAN port and my cable modem is DHCP. The router’s WAN MAC address is locked to the cable modem and must be 00 11 D8 80 B3 05. 4  Todo Fix the ACPI problem (seen on boot): http://www.lesswatts.org/projects/acpi/debug.php 1 The Adobe Acrobat reader program acroread has three levels of indirection: which acroread yields a symbolic link; the link target is a shell script; the shell script finally translates to the ELF file /opt/Adobe/Reader9/Reader/intellinux/bin/acroread. This document was translated from LATEX by HEVEA.