source/projects/archlinux/rollback.py

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2021-09-07 08:21:34 +00:00
import os
import re
import sys
def main(opts, args):
"""Usage: python rollback.py date
Parse /var/log/pacman.log, enumerating package transactions since the
specified date and building a plan for restoring the state of your system to
what it was at the specified date.
Assumes:
- /var/log/pacman.log has not been truncated
- /var/cache/pacman/pkg has not been flushed and still contains all required
packages
- The above paths are Arch default and have not been customized
- That it is not necessary to remove any "installed" packages
Note: no attempt is made to inspect the dependency graph of packages to be
downgraded to detect when a package is already transitively listed for
downgrading. This can create some annoying errors where eg. systemd will be
downgraded, meaning libsystemd will also be downgraded, but pacman considers
explicitly listing the downgrade of libsystemd when it will already be
transitively downgraded an error.
"""
date, = args
print("Attempting to roll back package state to that of {0}...\n"
.format(date),
file=sys.stderr)
# These patterns can't be collapsed because we want to select different
# version identifying strings depending on which case we're in. Not ideal,
# but it works.
# Ex. [2017-04-01 09:51] [ALPM] upgraded filesystem (2016.12-2 -> 2017.03-2)
upgraded_pattern = re.compile(
".*? upgraded (?P<name>\w+) \((?P<from>[^ ]+) -> (?P<to>[^\)]+)\)")
# Ex: [2018-02-23 21:18] [ALPM] downgraded emacs (25.3-3 -> 25.3-2)
downgraded_pattern = re.compile(
".*? downgraded (?P<name>\w+) \((?P<to>[^ ]+) -> (?P<from>[^\)]+)\)")
# Ex: [2017-03-31 07:05] [ALPM] removed gdm (3.22.3-1)
removed_pattern = re.compile(
".*? removed (?P<name>\w+) \((?P<from>[^ ]+)\)")
checkpoint = {}
flag = False
with open("/var/log/pacman.log") as logfile:
for line in logfile:
if date in line:
flag = True
elif not flag:
continue
match = re.match(upgraded_pattern, line)\
or re.match(downgraded_pattern, line)\
or re.match(removed_pattern, line)
if match:
package = match.group("name")
from_rev = match.group("from")
if package not in checkpoint:
checkpoint[package] = from_rev
continue
print("Checkpoint state:")
for k in checkpoint.keys():
print("{0} -> {1}".format(k, checkpoint[k]), file=sys.stderr)
pkgcache = "/var/cache/pacman/pkg"
pkgs = os.listdir(pkgcache)
pkgnames = ["{0}-{1}".format(k, v) for k, v in checkpoint.items()]
selected_pkgs = set([os.path.join(pkgcache, p)
for n in pkgnames
for p in pkgs
if n in p])
print("Suggested incantation:\n", file=sys.stderr)
print("sudo pacman --noconfirm -U {}"
.format("\\\n ".join(selected_pkgs)))
if __name__ == "__main__":
main(None, sys.argv[1:])