从 btrfs 快照中删除文件并仍然使用 btrfs 发送/接收？

Question

这确实是可能的（至少在我的实验中，它有效）。

首先删除侧面的文件send，拍摄快照，然后send使用receive可用于增量更新的任何现有快照进行增量更新。

现在，您将在远程端获得一个不包含相关文件的快照，并且您可以将其用于所有未来備份。

最后一件事是从所有老的快照。重要的是不要触碰你刚刚发送的快照，因为文件已经删除- 因为您需要保持不变，以便将其用作将来备份的父级。

因此，对于接收端的每个旧快照，使其可写，删除文件，然后（可选）再次使其只读。

以下是显示两个虚拟 btrfs 文件系统映像上进程的完整命令集：

set -x

echo "Make two btrfs images for our test"
dd if=/dev/zero bs=1M count=512 of=/tmp/img1.img
dd if=/dev/zero bs=1M count=512 of=/tmp/img2.img
losetup -f /tmp/img1.img
losetup -f /tmp/img2.img
mkfs.btrfs --mixed /dev/loop0
mkfs.btrfs --mixed /dev/loop1

echo "Mount them"
mkdir /tmp/sender /tmp/receiver
mount -t btrfs /dev/loop0 /tmp/sender
mount -t btrfs /dev/loop1 /tmp/receiver

btrfs subvolume create /tmp/sender/test

mkdir /tmp/sender/snaps
mkdir /tmp/receiver/snaps

echo "Create a 1 MB file, this is what we'll delete in the future"
dd if=/dev/urandom bs=1M count=1 of=/tmp/sender/test/f1

echo "Take our first snapshot, and send it"
btrfs subvolume snapshot -r /tmp/sender/test /tmp/sender/snaps/snap1
sync
btrfs send /tmp/sender/snaps/snap1 | btrfs receive /tmp/receiver/snaps

echo "Create a 2 MB file, snapshot, send and receive, using snap1 as parent"
dd if=/dev/urandom bs=2M count=1 of=/tmp/sender/test/f2
btrfs subvolume snapshot -r /tmp/sender/test /tmp/sender/snaps/snap2
sync
btrfs send -p /tmp/sender/snaps/snap1 /tmp/sender/snaps/snap2 | btrfs receive /tmp/receiver/snaps

echo "Now we can delete snap1 on the sender."
btrfs subvolume delete /tmp/sender/snaps/snap1

echo "Create a 3 MB file, snapshot send and receive, using snap2 as parent"
dd if=/dev/urandom bs=3M count=1 of=/tmp/sender/test/f3
btrfs subvolume snapshot -r /tmp/sender/test /tmp/sender/snaps/snap3
sync
btrfs send -p /tmp/sender/snaps/snap2 /tmp/sender/snaps/snap3 | btrfs receive /tmp/receiver/snaps

echo "Now we can delete snap2 on the sender."
btrfs subvolume delete /tmp/sender/snaps/snap2

echo "Delete the file we don't want anymore on the sender"
rm /tmp/sender/test/f1

echo "Snapshot, and send the deletion"
btrfs subvolume snapshot -r /tmp/sender/test /tmp/sender/snaps/snap4
btrfs send -p /tmp/sender/snaps/snap3 /tmp/sender/snaps/snap4 | btrfs receive /tmp/receiver/snaps

echo "Now we can delete snap3 on the sender - this will remove all reference to f1 on the sender"
btrfs subvolume delete /tmp/sender/snaps/snap3

echo "Confirm filesystem usage"
sync
btrfs filesystem du /tmp/sender/snaps/*
btrfs filesystem du /tmp/receiver/snaps/*

echo "Then, we can go and clean up the file in all backups on the receiver"
btrfs property set -t s /tmp/receiver/snaps/snap1 ro false
rm /tmp/receiver/snaps/snap1/f1
btrfs property set -t s /tmp/receiver/snaps/snap1 ro true

btrfs property set -t s /tmp/receiver/snaps/snap2 ro false
rm /tmp/receiver/snaps/snap2/f1
btrfs property set -t s /tmp/receiver/snaps/snap2 ro true

btrfs property set -t s /tmp/receiver/snaps/snap3 ro false
rm /tmp/receiver/snaps/snap3/f1
btrfs property set -t s /tmp/receiver/snaps/snap3 ro true

echo "Lastly, make sure incremental backups are still working against snap4"
echo "Create a 5 MB file, snapshot send and receive, using snap4 as parent"
dd if=/dev/urandom bs=5M count=1 of=/tmp/sender/test/f5
btrfs subvolume snapshot -r /tmp/sender/test /tmp/sender/snaps/snap5
sync
btrfs send -p /tmp/sender/snaps/snap4 /tmp/sender/snaps/snap5 | btrfs receive /tmp/receiver/snaps

echo "And see that usage is as we expect - all references to the 1MB file are gone."
sync
btrfs filesystem du /tmp/sender/snaps/*
btrfs filesystem du /tmp/receiver/snaps/*

echo "Clean up"
umount /tmp/sender /tmp/receiver
losetup -d /dev/loop0 /dev/loop1
rm /tmp/img1.img /tmp/img2.img

Answer 1