linux下的 btrfs¶
btrfs的功能¶
使用¶
btrfs filesystem du -s /path/to/subvolume
快照¶
用timeshift和snapper做快照。子卷布局
ID 257 gen 96108 top level 5 path @home
ID 318 gen 105959 top level 257 path @home/username
ID 268 gen 96108 top level 318 path @home/username/.snapshots
ID 269 gen 96108 top level 268 path @home/username/.snapshots/1/snapshot
ID 258 gen 105883 top level 5 path @root
ID 259 gen 105850 top level 5 path @cache
ID 260 gen 105959 top level 5 path @log
ID 261 gen 105942 top level 5 path @tmp
ID 262 gen 98722 top level 5 path @opt
ID 273 gen 96108 top level 262 path @opt/.snapshots
ID 274 gen 96108 top level 258 path @root/.snapshots
ID 285 gen 96433 top level 274 path @root/.snapshots/1/snapshot
ID 290 gen 105959 top level 5 path @
ID 519 gen 96445 top level 268 path @home/username/.snapshots/2/snapshot
ID 536 gen 103272 top level 5 path timeshift-btrfs/snapshots/2025-04-21_12-54-20/@
ID 537 gen 104133 top level 5 path timeshift-btrfs/snapshots/2025-04-21_20-12-43/@
即根目录用timeshift备份，并且回滚过一次（从@的ID可以看出来，不是安装时创建的256），而/home/username,/home/root,/home/opt用snapper做了几个快照
timeshift 备份根目录¶
注意btrfs的子卷布局，根目录必须是@，例如
ID 257 gen 96108 top level 5 path @home
ID 258 gen 105883 top level 5 path @root
ID 259 gen 105850 top level 5 path @cache
ID 260 gen 105930 top level 5 path @log
ID 261 gen 105928 top level 5 path @tmp
ID 262 gen 98722 top level 5 path @opt
ID 290 gen 105929 top level 5 path @
snapper 备份子卷¶
参考：
snapper更加灵活。首先创建一个snapper的配置文件
sudo snapper -c [name of config] create-config [path-to-subvol]
例如对根目录的备份配置，snapper默认配置名是root
sudo snapper -c root create-config /
snapper默认会创建子卷/.snapshots，似乎是opensuse风格的，把它调整成一般的布局
sudo umount /.snapshots
sudo rm -r /.snapshots
sudo btrfs subvolume delete /.snapshots
sudo mkdir /.snapshots
sudo mount -o subvol=/ /dev/nvme0n1p1 /mnt
sudo btrfs subvolume create /mnt/@snapshots
可以对其他子卷做同样的操作，比如对/opt (@opt),/root (@root)。
对用户目录，首先有@home子卷挂载/home，然后用
useradd
Usage: useradd [options] LOGIN
useradd -D
useradd -D [options]
Options:
--btrfs-subvolume-home use BTRFS subvolume for home directory
选项创建@home/user_name子卷挂载用户家目录/home/user_name。这样再用上述方法可以对特定用户的家目录做快照。子卷会像
从快照中恢复¶
对snapper创建的/的快照，复杂的手动方法，要从live
USB开始，就是安装arch时的live系统
sudo mount /dev/nvme0n1p6 /mnt
cd /mnt
sudo mv /mnt/@ /mnt/@.broken
sudo btrfs subvolume snapshot /mnt/@snapshots/{number}/snapshot /mnt/@
sudo btrfs subvolume delete /mnt/@.broken
不进入live系统的方法，看上去很危险，最好回滚后立刻重启
sudo mount -o subvol=/ /dev/nvme0n1p1 /mnt
sudo btrfs subvolume snapshot /mnt/@ /mnt/@bad
sudo btrfs subvolume delete /mnt/@
sudo btrfs subvolume snapshot /mnt/@snapshots/要恢复的快照号/snapshot /mnt/@
可以用脚本完成回滚（来自这里）
#!/bin/sh
set -e
if [[ x"$1" == x ]]; then
echo "No snapshot number given." 1>&2
echo "Usage: rollback [snapshot to rollback]" 1>&2
exit 1
fi
root_dev=`findmnt -n -o SOURCE / | sed 's/\[.*\]//g'`
root_subvol=`findmnt -n -o SOURCE / | sed 's/.*\[\(.*\)\].*/\1/'`
echo ">= Rollback to #$1 on device $root_dev"
# create snapshot before
sudo snapper create --read-only --type single -d "Before rollback to #$1" --userdata important=yes
sudo mount -o subvol=/ $root_dev /mnt
# check enviornment
if [[ x"$root_subvol" == x/@ ]]; then
echo "Warning: Not run in a snapshot, a subvolume @old will be created. You should consider remove it after reboot." 1>&2
if [[ -d /mnt/@old ]]; then
echo "Found last @old, remove it."
sudo btrfs subvolume delete /mnt/@old >/dev/null
fi
sudo mv /mnt/@ /mnt/@old
else
sudo btrfs subvolume delete /mnt/@ >/dev/null
fi
sudo btrfs subvolume snapshot /mnt/@snapshots/$1/snapshot /mnt/@ >/dev/null
sudo umount /mnt
其他子卷的snapper快照，直接用
snapper -c [config] rollback [number]
对于timeshift，直接gui操作就行。
回滚后最好立刻重启。