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App-Transpierce-0.002
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/ App::Transpierce

NAME

App::Transpierce - backup and modify important files

SYNOPSIS

# exports the script into the current directory
transpierce --self-export

# copies the script to the server
scp transpierce myuser@remote:~/transpierce

# log into the server, create a directory for the current task
ssh myuser@remote
mkdir dirty_production_task

# create transpierce.conf file, which describes files to be altered
echo "target /production/directory" >> dirty_production_task/transpierce.conf
echo "production/file.ext" >> dirty_production_task/transpierce.conf

# see what actions will be taken
transpierce --describe dirty_production_task

# set up the environment for that task
transpierce dirty_production_task

# recommended: verify the contents of .sh files
cat dirty_production_task/*.sh

# recommended: set up a git repository (if it is available)
cd dirty_production_task
git init
git add -A
git commit -m "Initial setup"

DESCRIPTION

This distribution provides transpierce script which can be used for per-task management of files which must be backed up before modification.

Transpierce means to pierce through. The module makes it easier penetrate system files and alter them by working on local copies. You only poke single holes in it by performing file deployment and (if needed) backup restoration. If you think that's not how it's supposed to be done, you're right - but sometimes it is what needs to be done.

Suppose you must reproduce a bug that only happens under a very specific environment. Or you have to quickly hotfix something and full release cycle will not be fast enough. Do you change live files? Or make copies as backups and then do modifications? Are you sure you restored all unwanted changes?

This script will set up a small working environment for you, which consists of:

  • restore directory, containing original files (not meant to be changed)

  • deploy directory, where you can make your changes

  • restore.sh script, which will restore original files from restore directory

  • deploy.sh script, which will copy files to their locations from deploy directory

  • diff.sh script, which will check whether files in restore directory differ from original files

This environment is best made in your home directory, far away from important files.

Configuration

The list of files is set using transpierce.conf file. Each file is in its own line:

/prod/lib/System.pm
/prod/script.pl
/etc/apache2/sites-available/mysite.conf

During copying the files to restore and deploy their paths are flattened, like so:

__prod__lib__System.pm
__prod__script.pl
__etc__apache2__sites-available__mysite.conf

If files in your transpierce.conf contain whitespace, you will need to quote using either single or double quotes:

target "/dir/with space/file_with_space"

You can use relative paths in the configuration:

../dir/file1

This path will be transformed into this (double dot replaced with UP word):

UP__dir__file1

It must be relative to the location of configuration file, not to the location from which you run transpierce! When in doubt, use absolute paths.

Targets

You can set targets in transpierce.conf:

target /prod
	lib/System.pm
	script.pl
target /etc/apache2
	sites-available/mysite.conf

Which will change the local paths like this:

__prod/lib__System.pm
__prod/script.pl
__etc__apache2/sites-available__mysite.conf

Now two local directories will be created: __prod and __etc__apache2. This way the directory structure of working copies can be less chaotic by maintaining context with a single directory for each target.

New files

It's possible to create new files:

new 0777 user group "../file.txt"
target ".."
	new 0777 user group "../file2.txt"

For such files:

  • they will be created (empty) in deploy directory

  • they will not exist in restore directory

  • deploy.sh will create full directory path to them with default permissions

  • restore.sh will remove these files altogether (but not the directories)

  • diff.sh will ls -l these files

  • three words used after new will be used for chmod, chown and chgrp respectively and are required

  • file permissions must be octal number in form of 0NNN (cannot be +x for example)

Scripts

transpierce script is only used once during initialization. After that, work is performed using generated shell scripts.

This design choice does two things:

  • lets you audit the contents of the files to see whether they do what is advertised and do not break anything else

  • makes it trivial to do any modifications

Both restore.sh and deploy.sh scripts copy each file back into their original locations from the corresponding directory, then change their mode, uid and gid back to what it was during the initialization. You might require root permissions to run those scripts, depending on files' original locations and permissions.

diff.sh script can be run to make sure file contents in restore directory do not differ from original files. It is recommended to do that before running deploy.sh script. If there are differences, it's possible that original files were updated in the meantime and current working environment needs to be initialized again.

Taking it with you

App::Transpierce was written with the ability to take it with you in mind. It is fully compatible with perl 5.10.0, uses no non-core runtime dependencies and is self-contained. You don't have to install the CPAN module on the target server (which is often hard or impossible). You can instead install the module locally, export the script and copy it into target server:

cpanm App::Transpierce
transpierce --self-export
scp transpierce myuser@remote:~/transpierce

App::Transpierce and git

If the server on which you want to use the application has git, it is highly recommended to initialize the repository and make a commit after initializing the working environment. This lets you:

  • double-check what changes were made before running deploy.sh, by running git diff

  • export the changes, for example to also apply them to the application main repository, by running git diff > changes.diff

  • apply diffs from outside using git apply changes.diff

  • provide more content on when was this worked on

  • many more...

Portability

This module is meant to be used on Unix (Linux, BSD) servers. No effort was made to make it useful in other environments, mainly because the author only knows how to administer Unix servers.

AUTHOR

Bartosz Jarzyna, <bbrtj.pro@gmail.com>

COPYRIGHT AND LICENSE

Copyright (C) 2023 by Bartosz Jarzyna

FreeBSD 2-clause license - see bundled LICENSE.