Pmbootstrap development guide

From postmarketOS
Jump to: navigation, search

Installation code (pmb.install.*)

Whenever you change the installation process, also adjust the recovery zip installer (which performs a good part of the installation procedure directly on the Android device with a shell script).

What is this args variable used everywhere?

See the big comment at the top of pmb/helpers/args.py.

Executing shell commands

Use one of the following functions instead of Python's built in subprocess:

These functions call pmb.helpers.run_core.core() internally to write to the log file (that you can read with pmbootstrap log) and timeout when there is no output. A lot of function parameters are passed through to core() as well, see its docstring for a detailed description of what these parameters do.

Writing to files

See also: #1316 Properly escape commands in pmb.chroot.user()

The passed commands gets interpreted as single command, and not executed in a shell. This means something like the following will not work:

pmb.chroot.root(args, ["echo", "test", ">", "/tmp/test"])

Instead, if you need shell functionality in the call, you can wrap the call with sh -c. Here's one example with the parameters correctly escaped (you don't need to do that for the strings in this example, but if you pass variables then they should be escaped properly):

shell_cmd = "echo " + shutil.quote("test") + " > " + shutil.quote("/tmp/test")
pmb.chroot.root(args, ["sh", "-c", shell_cmd])

Another technique (especially if you need to run many commands in the shell at once) is writing all commands down into a temporary file and executing it with the shell, see for example pmb/chroot/initfs.py.

Writing files to the chroot

The users in the chroots (root and pmos) have different user IDs than the user of the host system. Therefore we can't just write a file to anywhere in the chroot. But we can write to /tmp and move the file afterwards:

with open("tmp/somefile", "w") as handle:
    handle.write("It works")
pmb.chroot.root(args, ["mv", "/tmp/somefile", "/etc/somefile"])

See also