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NAME |
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Urlader - installer-less single-file independent executables |
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|
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SYNOPSIS |
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use Urlader; |
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|
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DESCRIPTION |
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Urlader (that's german for "bootloader" btw.) was created out of |
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frustration over PAR always being horribly slow, again not working, |
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again not being flexible enough for simple things such as software |
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upgrades, and again causing mysterious missing file issues on various |
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platforms. |
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|
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That doesn't mean this module replaces PAR, in fact, you should stay |
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with PAR for many reasons right now, user-friendlyness is one of them. |
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|
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However, if you want to make single-file distributions out of your perl |
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programs (or python, or C or whatever), and you are prepared to fiddle a |
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LOT, this module might provide a faster and more versatile deployment |
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technique then PAR. Well, if it ever gets finished. |
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|
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Also, *nothing in this module is considered very stable yet*, and it's |
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far from feature-complete. |
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|
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Having said all that, Urlader basically provides three services: |
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|
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A simple archiver that packs a directory tree into a single file. |
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A small C program that works on windows and unix, which unpacks an |
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attached archive and runs a program (perl, python, whatever...). |
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A perl module support module (*this one*), that can be used to query the |
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runtime environment, find out where to install updates and so on. |
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|
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EXAMPLE |
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How can it be used to provide single-file executables? |
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|
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So simple, create a directory with everything that's needed, e.g.: |
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|
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# find bintree |
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bintree/perl |
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bintree/libperl.so.5.10 |
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bintree/run |
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bintree/pm/Guard.pm |
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bintree/pm/auto/Guard/Guard.so |
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bintree/pm/XSLoader.pm |
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bintree/pm/DynaLoader.pm |
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bintree/pm/Config.pm |
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bintree/pm/strict.pm |
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bintree/pm/vars.pm |
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bintree/pm/warnings.pm |
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|
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# cat bintree/run |
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@INC = ("pm", "."); # "." works around buggy AutoLoader |
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use Guard; |
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guard { warn "hello, world!\n" }; # just to show off |
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exit 0; # tell the urlader that everything was fine |
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|
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Then pack it: |
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|
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# wget http://urlader.schmorp.de/prebuilt/1.0/linux-x86 |
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# urlader-util --urlader linux-x86 --pack myprog ver1_000 bintree \ |
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LD_LIBRARY_PATH=. ./perl run \ |
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>myprog |
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# chmod 755 myprog |
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|
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The packing step takes a binary loader and appends all the files in the |
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directory tree, plus some meta information. |
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|
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The resulting file is an executable that, when run, will unpack all the |
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files and run the embedded program. |
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|
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CONCEPTS |
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urlader |
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A small (hopefully) and relatively portable (hopefully) binary that |
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is prepended to a pack file to make it executable. |
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|
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You can build it yourself from sources (see prebuilt/Makefile in the |
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distribution) or use one of the precompiled ones at: |
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|
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http://urlader.schmorp.de/prebuilt/1.0/ |
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|
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The README there has further information on the binaries provided. |
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|
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exe_id |
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A string that uniquely identifies your program - all branches of it. |
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It must consist of the characters "A-Za-z0-9_-" only and should be a |
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valid directory name on all systems you want to deploy on. |
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|
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exe_ver |
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A string the uniquely identifies the contents of the archive, i.e. |
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the version. It has the same restrictions as the "exe_id", and |
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should be fixed-length, as Urlader assumes lexicographically higher |
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versions are newer, and thus preferable. |
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|
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pack file (archive) |
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This contains the "exe_id", the "exe_ver", a number of environment |
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variable assignments, the program name to execute, the initial |
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arguments it receives, and finally, a list of files (with contents |
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:) and directories. |
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|
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override |
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When the urlader starts, it first finds out what "exe_id" is |
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embedded in it. It then looks for an override file for this id |
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($URLADER_EXE_DIR/override) and verifies that it is for the same |
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"exe_id", and the version is newer. If this is the case, then it |
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will unpack and run the override file instead of unpacking the files |
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attched to itself. |
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|
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This way one can implement software upgrades - download a new |
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executable, write it safely to disk and move it to the override |
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path. |
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|
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ENVIRONMENT VARIABLES |
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The urlader sets and maintains the following environment variables, in |
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addition to any variables specified on the commandline. The values in |
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parentheses are typical (but not gauranteed) values for unix - on |
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windows, ~/.urlader is replaced by %AppData%/urlader. |
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|
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URLADER_VERSION (1.0) |
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Set to the version of the urlader binary itself. All versions with |
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the same major number should be compatible to older versions with |
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the same major number. |
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|
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URLADER_DATADIR (~/.urlader) |
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The data directory used to store whatever urlader needs to store. |
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|
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URLADER_CURRDIR |
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This is set to the full path of the current working directory where |
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the urlader was started. Atfer unpacking, the urlader changes to the |
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"URLADER_EXECDIR", so any relative paths should be resolved via this |
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path. |
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|
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URLADER_EXEPATH |
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This is set to the path of the urlader executable itself, usually |
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relative to $URLADER_CURRDIR. |
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|
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URLADER_EXE_ID |
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This stores the executable id of the pack file attached to the |
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urlader. |
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|
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URLADER_EXE_VER |
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This is the executable version of the pack file attached to the |
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urlader, or the override, whichever was newer. Or in other words, |
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this is the version of the application running at the moment. |
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|
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URLADER_EXE_DIR (~/.urlader/$URLADER_EXE_ID> |
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The directory where urlader stores files related to the executable |
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with the given id. |
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|
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URLADER_EXECDIR (~/.urlader/$URLADER_EXE_ID/i-$URLADER_EXE_VER) |
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The directory where the files from the pack file are unpacked and |
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the program is being run. Also the working directory of the program |
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when it is run. |
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|
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URLADER_OVERRIDE (empty or override) |
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The override file used, if any, relative to $URLADER_EXECDIR. This |
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is either missing, when no override was used, or the string |
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override, as thta is currently the only override file urlader is |
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looking for. |
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|
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FUNCTIONS AND VARIABLES IN THIS MODULE |
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$Urlader::URLADER_VERSION |
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Set to the urlader version ("URLADER_VERSION") when the program is |
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running form within urlader, undef otherwise. |
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|
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$Urlader::DATADIR, $Urlader::EXE_ID, $Urlader::EXE_VER, |
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$Urlader::EXE_DIR, $Urlader::EXECDIR |
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Contain the same value as the environment variable of the (almost) |
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same name. You should prefer these, though, as these might even be |
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set to correct values when not running form within an urlader |
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environment. |
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|
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Urlader::set_exe_info $exe_id, $exe_ver |
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Sets up the paths and variables as if running the given executable |
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and version from within urlader. |
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|
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$lock = Urlader::lock $path, $exclusive, $wait |
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Tries to acquire a lock on the given path (which must specify a file |
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which will be created if necessary). If $exclusive is true, then it |
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tries to acquire an exclusive lock, otherwise the lock will be |
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shared. If $wait is true, then it will wait until the lock can be |
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acquired, otherwise it only attempts to acquire it and returns |
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immediately if it can't. |
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|
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If successful it returns a lock object - the lock will be given up |
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when the lock object is destroyed or when the process exits (even on |
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a crash) and has a good chance of working on network drives as well. |
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|
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If the lock could not be acquired, "undef" is returned. |
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|
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This function is provided to assist applications that want to clean |
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up old versions, see "TIPS AND TRICKS", below. |
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|
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TIPS AND TRICKS |
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Gathering files |
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Gathering all the files needed for distribution can be a big |
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problem. Right now, Urlader does not assist you in this task in any |
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way, however, just like perl source stripping, it is planned to |
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unbundle the relevant technology from staticperl |
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(<http://staticperl.plan9.de>) for use with this module. |
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|
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You could always use par to find all library files, unpack the |
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bundle and add perl, libperl and other support libraries (e.g. |
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libgcc_s). |
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|
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Software update |
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Updating the software can be done by downloading a new packfile |
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(with the same "exe_id" but a higher "exe_ver" - this can simply be |
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the executable you create when making a release) and replacing the |
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override file in the $URLADER_EXE_DIR. |
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|
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When looking for updates, you should include $URLADER_VERSION, |
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$URLADER_EXE_ID and $URLADER_EXE_VER - the first two must be |
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identical for update and currently running program, while the last |
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one should be lexicographically higher. |
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|
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Replacing the override file can be done like this: |
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|
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rename "new-override.tmp", "$Urlader::EXE_DIR/override" |
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or die "could not replace override"; |
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|
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This can fail on windows when another urlader currently reads it, |
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but should work on all platforms even when other urlader programs |
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execute concurrently. |
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|
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Cleaning up old directories |
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Urlader only packs executables once and then caches them in the |
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$URLADER_EXECDIR. After upgrades there will be old versions in there |
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that are not being used anymore. Or are they? |
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|
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Each instance directory (i-*) in the $URLADER_EXE_DIR) has an |
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associated lock file (i-*.lck) - while urlader executes an app it |
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keeps a shared lock on this file. |
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|
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To detect whether a version is in use or not, you must try to |
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acquire an exclusive lock, i.e.: |
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|
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my $lock = Urlader::lock "~/.urlader/myexe/i-ver01.lck", 1, 0; |
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if (!$lock) { |
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# instance dir is not in use and can be safely deleted |
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} |
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|
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If an older urlader wants to use an instance that was deleted or is |
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currently being deleted it will wait until it's gone and simply |
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recreate it, so while less efficient, deleting instance directories |
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should always be safe. |
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|
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The lockfile itself can be deleted as long as you have an exclusive |
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lock on it (if your platform allows this). |
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|
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A real world project |
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The only real world project using this that I know of at the moment |
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is the deliantra client (http://www.deliantra.net for more info). |
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|
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It uses some scary scripts to build the client and some dependnet |
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modules (build.*), to gather perl source files into a distribution |
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tree, shared objects and system shared libraries (some of which have |
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to be patched or, due to the horrible dll hell on OS X, even |
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renamed), called "gatherer", and a script called "gendist" to build |
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executable distributions. |
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|
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These can be found at |
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<http://cvs.schmorp.de/deliantra/Deliantra-Client/util/>, but |
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looking at them can lead to premature blindless. |
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|
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Shared Libraries |
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It is often desirable to package shared libraries - for example the |
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Deliantra client packages SD>, Berkely DB, Pango and amny other |
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libraries that are unlikely to be available on the target system. |
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|
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This usually requires some fiddling (see below), and additionally |
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some environment variables to be set. |
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|
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For example, on ELF systems you usually want LD_LIBRARY_PATH=. and |
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on OS X, you want DYLD_LIBRARY_PATH=. (these are effectively the |
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default on windows). |
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|
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These can most easily be specified when building the packfile: |
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|
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urlader-util ... LD_LIBRARY_PATH=. ./perl run |
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|
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Portability: RPATH |
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Often perl is linked against a shared libperl.so - and might be so |
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using an rpath. Perl extensikns likewise might use an rpath, which |
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means the binary will mostly ignore LD_LIBRARY_PATH, which leads to |
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trouble. |
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|
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There is an utility called chrpath, whose -d option can remove the |
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rpath from binaries, shared library and shared objects. |
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|
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Portability: OS X DLL HELL |
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OS X has the most severe form of DLL hell I have seen - if you link |
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against system libraries, which is practically unavoidable, you get |
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libraries of well-known names (e.g. libjpeg) that have nothing to do |
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with what you normally expect libjpeg to be, and there is no way to |
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get your version of libjpeg into your program. |
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|
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Moreover, even if apple ships well-known libraries (e.g. libiconv), |
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they often ship patched versions which have a different ABI or even |
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API then the real releases. |
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|
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The only way aorund this I found was to change all library names in |
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my releases (libjpeg.dylib becomes libdeliantra-jpeg.dylin and so |
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on), by patching the paths in the share dlibraries and shared |
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objects. install-name-tool (with -id and -change) works in many |
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cases, but often paths are embedded indirectly, so you might have to |
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use a *dirty* string replacement. |
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|
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SECURITY CONSIDERATIONS |
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The urlader executable itself does not support setuig/setgid operation, |
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or running with elevated privileges - it does no input sanitisation, and |
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is trivially exploitable. |
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|
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AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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|
