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標題: gentoo 用 btrfs zram 記 [打印本頁]

作者: cal22cal 時間: 2015-8-26 19:51 標題: gentoo 用 btrfs zram 記

本帖最後由 cal22cal 於 2015-8-27 09:32 編輯

唔好話我空手套白狼, 都吹吓水咁啦,
以下有啲係 gentoo 嘢, 唔知噏乜就 skip 算, 唔好嘥時間睇

話說部ok垃圾機 up 咗去 8G ram,
又行得順咗好多,
free 返啲 hdd 位, 又起多個 vm 玩吓

btrfs pros & cons 唔吹, 不過有啲嘢又可以噏吓
有啲 distro, 都叫人 set 個 default root sysvolume
嚟 boot / , 如果要 boot old snapshot sysvolume 又要 set 過,

亦都有好多方法, e.g. 改 fstab, set 個 default root sysvolume ...
大多數都要 boot 多一次機, 先可以用個 old snapshot sysvolume
咁樣有乜方法, 可以唔洗改 fstab, 轉 boot sysvolume ...
嚟 boot 個 snapshot
好懶嘅我, 經 google 大神指示係咁, 改 fstab

LABEL=XXX / btrfs rw,noatime,compress=lzo,autodefrag 0 0

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冇咗 subvol=root_subvol_name 呢個 option
注意 fstab btrfs fsck flags 係全 0

grub2 唔識, 仲係用緊 grub lagecy
冇 set 過 default subvolume
用 kernel command 嚟指定個 / sysvolume, e.g.
root filesystem 個 sysvolume 係 ROOT-FS

title ROOT-FS 4.1.6-gentoo
root (hd0,1)
kernel /kernel-genkernel-x86_64-4.1.6-gentoo root=UUID=xxx-xxx-xxx-xxx [color=Blue]rootflags=subvol=ROOT-FS[/color]
initrd /initramfs-genkernel-x86_64-4.1.6-gentoo

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响 /boot dir 道, 係

ln -snf kernel-genkernel-x86_64-4.1.6-gentoo snap-kernel
ln -snf initramfs-genkernel-x86_64-4.1.6-gentoo snap-initramfs

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每一次 upgrade kernel 都 update 條 link 一次,
當然, menu.lst 要加 entry for new kernel

咁樣造 / snapshot 嗰時, 就造多幾個, 冇壞,
1. snapshot--time.stamp
2. snapshot--ROOT_FS_0
3. snapshot--ROOT_FS_1
play safe, 3 個完全一樣

再响 grub.conf add 多條 entry

title snapshot-ROOT-FS_1
root (hd0,1)
kernel /snap-kernel root=UUID=xxx-xxx-xxx-xxx [color=Blue]rootflags=subvol=snapshot-ROOT-FS_1[/color]
initrd /snap-initramfs

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咁樣就可以直 boot latest backup/snapshot root fs

小心, boot 完 backup sanpshot, 如果頭先個 ROOT-FS sysvolume
要 rollback to latest snapshot, wiki 話,
要 del 咗, 先好整 snapshot, i.e.
响 reboot 之前,
mv /path/ROOT-FS /path/problem
or
btrfs subvol delete -C /path/ROOT-FS && \
btrfs subvolume snapshot /path/snapshot-ROOT-FS_1 /path/ROOT-FS
唔好直接 overwrite

希望冇吹錯嘢啦

原本仲想吹 swap under zram, 不過太長, 下一次先算

edit:-
zram added.

作者: cal22cal 時間: 2015-8-27 08:59

btrfs 原來仲有嘢未講完,

snapshot / 個 file time stamp 唔夾 ls -lQrtHh
要 touch / 咗先做 snapshot

fstab
# BTRFS btrfs disk top
LABEL=XXX /mnt/TOP btrfs defaults,noauto,subvolid=0 0 0

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#!/bin/bash
mkdir -p /boot.bak.for.snapshot
mount /boot
# backup /boot
echo "backup /boot to /boot.bak.for.snapshot"
rsync -avc --delete --exclude 'lost+found' /boot/ /boot.bak.for.snapshot
umount /boot && echo "umount /boot ... ok"
mount /mnt/TOP
btrfs subvol delete -C /mnt/TOP/snapshot-ROOT-FS_0 && \
btrfs subvol delete -C /mnt/TOP/snapshot-ROOT-FS_1 && \
touch /mnt/TOP/ROOT-FS && \
btrfs subvolume snapshot /mnt/TOP/ROOT-FS /mnt/TOP/snapshot-ROOT-FS_0 && \
btrfs subvolume snapshot /mnt/TOP/ROOT-FS /mnt/TOP/snapshot-ROOT-FS_1 && \
btrfs subvolume snapshot /mnt/TOP/ROOT-FS /mnt/TOP/snapshot-ROOT-FS--`date +\%Y-\%m-\%d_\%H.\%M.\%S`

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又試過用 aoe 過 file 去 vm btrfs portage,
fs 炒咗粉, 要 restore backup from external usb hdd

作者: cal22cal 時間: 2015-8-27 09:31

2. zram

config ZRAM
tristate "Compressed RAM block device support"
depends on BLOCK && SYSFS && ZSMALLOC

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响 gentoo zram wiki kernel options 少咗嘢
https://wiki.gentoo.org/wiki/Zram#Kernel_configuration
要加

Processor type and features --->
<M> Memory allocator for compressed pages
[*] Use page table mapping to access object in zsmalloc
[*] Export zsmalloc statistics

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如果要 compile 大 pkg under ram disk, 可以將 /tmp 加到好大,
要 swap 就去咗 zram 嘅 swap

fstab
# RAM disks
/dev/shm /tmp tmpfs size=8G,nosuid,nodev,relatime 0 0

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當然要睇情況, 唔可以夾硬嚟

cat /etc/conf.d/zram-init
load_on_start="yes"
unload_on_stop="yes"
num_devices="1"
type0="swap"
flag0="" # The default "16383" is fine for us
size0="1024"
maxs0="4" # maximum number of parallel processes for this device
algo0="lz4" # lz4 is faster than lzo

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