Re: [心得] 閒聊+雙系統另種選擇 loopdevice

[czm (czm)]

本次一樣修改initrd.d/linuxrc
新增可OverlayFS boot
同樣是新增修改這三部份

: part1: 參數讀取
放在參數讀取的那區

: part2: 解析UUID=, LABEL=; mount and losetup.
放在 Determine root device 前

: part3: mount --move
放在switch_root 前


在grub.cfg內的用法,舉例三種:
1. 最初的版本 只用單一loopfile 啟動os
linux vmlinuz loops_dev=LABEL=loops loops_mnt=/loops \
loop_file=live.ext4 root=LABEL=live

2. 使用overlay boot, 但lower,upper,work都在同一可寫的目錄下
linux vmlinuz rootfstype=overlay ovl_dev1=LABEL=loops ovl_mnt1=/loops \
ovl_loopfile1=live/live.ext4 ovl_mnt1_sub=/loops/live/lower \
ovl_mnt2_sub=/loops/live root=overlay

3. 使用overlay, lower來源為squashfs, upper與work使用tmpfs
linux vmlinuz rootfstype=overlay ovl_dev1=LABEL=cd ovl_mnt1=/loops \
ovl_loopfile1=live.squashfs ovl_mnt1_sub=/lower \
ovl_dev2=tmpfs ovl_mnt2=/rw ovl_mnt2_opt=size=3072m root=overlay

接著預計自製 live-cd...

: 以下為與原檔initrd.d/linuxrc[C比較 新增的內容
: ====================================

                # zm 1: get parameters for boot from loop file or overlayfs
                loops_dev=*)
                        LOOPS_DEV=${x#*=}
                ;;
                loops_mnt=*)
                        LOOPS_MNT=${x#*=}
                ;;
                loop_file=*)
                        LOOP_FILE=${x#*=}
                ;;
                ovl_dev1=*)
                        OVL_DEV1=${x#*=}
                ;;
                ovl_dev2=*)
                        OVL_DEV2=${x#*=}
                ;;
                ovl_mnt1=*)
                        OVL_MNT1=${x#*=}
                ;;
                ovl_mnt2=*)
                        OVL_MNT2=${x#*=}
                ;;
                ovl_mnt2_opt=*)
                        OVL_MNT2_OPT=${x#*=}
                ;;
                ovl_loopfile1=*)
                        OVL_LOOPFILE1=${x#*=}
                ;;
                ovl_loopfile2=*)
                        OVL_LOOPFILE2=${x#*=}
                ;;
                ovl_mnt1_sub=*)
                        OVL_MNT1_SUB=${x#*=}
                ;;
                ovl_mnt2_sub=*)
                        OVL_MNT2_SUB=${x#*=}
                ;;
                mount_move)
                        MOUNT_MOVE=1
                ;; # zm
------------
# zm 2: find the device which contains loop files, mount and losetup.
if [ -n "${LOOPS_DEV}" ]; then
        if [ -z "${LOOPS_MNT}" ]; then
                LOOPS_MNT='/loops'
        fi
        MNT_DEV=""
        while [ "${MNT_DEV}" = '' ]
        do
                case "${LOOPS_DEV}" in
                        LABEL=*|UUID=*)
                                retval=1
                                if [ ${retval} -ne 0 ]; then
                                        MNT_DEV=$(findfs "${LOOPS_DEV}" )
                                        retval=$?
                                fi
                                if [ ${retval} -ne 0 ]; then
                                        MNT_DEV=$(busybox findfs "${LOOPS_DEV}" )
#                                       MNT_DEV=$(busybox findfs "${LOOPS_DEV}" 2>/dev/null)
                                        retval=$?
                                fi
                                if [ ${retval} -ne 0 ]; then
                                        MNT_DEV=$(blkid -o device -l -t "${LOOPS_DEV}")
                                        retval=$?
                                fi
                                if [ ${retval} -eq 0 ] && [ -n "${MNT_DEV}" ]; then
                                        good_msg "Detected loops_dev=${MNT_DEV}"
                                else
                                        prompt_user "MNT_DEV" "block device"
                                        continue
                                fi
                                ;;
                esac
        done;
        if [ -n "${LOOP_FILE}" ]; then
                mkdir -p ${LOOPS_MNT}
                mount ${MNT_DEV}  ${LOOPS_MNT}
                losetup /dev/loop0 "${LOOPS_MNT}/${LOOP_FILE}"
        fi
fi
# zm 2-1: find the devices, loopfiles, dirs for overlay fs.
if [ "${ROOTFSTYPE}" = 'overlay' ]; then
        OVL_MNT_DEV1=""
        while [ "${OVL_MNT_DEV1}" = '' ]
        do
                case "${OVL_DEV1}" in
                        LABEL=*|UUID=*)
                                retval=1
                                if [ ${retval} -ne 0 ]; then
                                        OVL_MNT_DEV1=$(findfs "${OVL_DEV1}" )
                                        retval=$?
                                fi
                                if [ ${retval} -ne 0 ]; then
                                        OVL_MNT_DEV1=$(busybox findfs "${OVL_DEV1}" )
#                                       OVL_MNT_DEV1=$(busybox findfs "${OVL_DEV1}" 2>/dev/null)
                                        retval=$?
                                fi
                                if [ ${retval} -ne 0 ]; then
                                        OVL_MNT_DEV1=$(blkid -o device -l -t "${OVL_DEV1}")
                                        retval=$?
                                fi
                                if [ ${retval} -eq 0 ] && [ -n "${OVL_MNT_DEV1}" ]; then
                                        good_msg "Detected ovl_dev1=${OVL_MNT_DEV1}"
                                else
                                        prompt_user "ovl_dev1" "${OVL_DEV1}" "failed"
                                        continue
                                fi
                                ;;
                esac
        done;
    if [ -n "${OVL_MNT_DEV1}" ] && [ -n "${OVL_MNT1}" ]; then
        mkdir -p ${OVL_MNT1}
        mount ${OVL_MNT_DEV1}  ${OVL_MNT1}
        if [ "$?" = '0' ]; then
                OVL_DEV1_MOUNTED=1
        else
                OVL_DEV1_MOUNTED=0
        fi
    fi
    if [ "${OVL_DEV1_MOUNTED}" = '1' ]; then
        if [ -n "${OVL_LOOPFILE1}" ]; then
            if [ -z "${OVL_MNT1_SUB}" ]; then
                OVL_MNT1_SUB="/lower"
            fi
            mkdir -p "${OVL_MNT1_SUB}"
            losetup /dev/loop0 "${OVL_MNT1}/${OVL_LOOPFILE1}"
            mount /dev/loop0 "${OVL_MNT1_SUB}"
#               mount -t squashfs -o loop "${OVL_MNT1}/${OVL_LOOPFILE1}" "${OVL_MNT1_SUB}"
            LOWER="lowerdir=${OVL_MNT1_SUB}"
        else
            if [ -n "${OVL_MNT1_SUB}" ]; then
                LOWER="lowerdir=${OVL_MNT1_SUB}"
            else
                LOWER="lowerdir=${OVL_MNT1}"
            fi
        fi
        got_good_root=1
    fi
    if [ -n "${OVL_DEV2}" ]; then
     if [ "${OVL_DEV2}" = 'tmpfs' ]; then
            if [ -z "${OVL_MNT2_OPT}" ]; then
                OVL_MNT2_OPT='size=3072m'
            fi
            mkdir -p "${OVL_MNT2}"
            mount -t tmpfs -o "${OVL_MNT2_OPT}" tmpfs "${OVL_MNT2}"
            good_msg "Mounting -t ovl_dev2=${OVL_DEV2} -o ${OVL_MNT2_OPT} tmpfs ${OVL_MNT2}"
            UPPER="upperdir=${OVL_MNT2}/upper"
            mkdir -p "${OVL_MNT2}/upper"
            WORK="workdir=${OVL_MNT2}/work"
            mkdir -p "${OVL_MNT2}/work"
     else
        OVL_MNT_DEV2=""
        while [ "${OVL_MNT_DEV2}" = '' ]
        do
            case "${OVL_DEV2}" in
                LABEL=*|UUID=*)
                    retval=1
                    if [ ${retval} -ne 0 ]; then
                        OVL_MNT_DEV2=$(findfs "${OVL_DEV2}" )
                        retval=$?
                    fi
                    if [ ${retval} -ne 0 ]; then
                        OVL_MNT_DEV2=$(busybox findfs "${OVL_DEV2}" )
                        retval=$?
                    fi
                    if [ ${retval} -ne 0 ]; then
                        OVL_MNT_DEV2=$(blkid -o device -l -t "${OVL_DEV2}")
                        retval=$?
                    fi
                    if [ ${retval} -eq 0 ] && [ -n "${OVL_MNT_DEV2}" ]; then
                        good_msg "Detected ovl_dev2=${OVL_MNT_DEV2}"
                    else
                        prompt_user "Maybe ovl_dev2 ${OVL_DEV2} failed"
                        continue
                    fi
                    ;;
            esac
        done;
        if [ -n "${OVL_MNT_DEV2}" ] && [ -n "${OVL_MNT2}" ]; then
            mkdir -p ${OVL_MNT2}
            mount ${OVL_MNT_DEV2}  ${OVL_MNT2}
            if [ -z "${OVL_LOOPFILE2}" ]; then
                UPPER="upperdir=${OVL_MNT2}/upper"
                mkdir -p "${OVL_MNT2}/upper"
                WORK="workdir=${OVL_MNT2}/work"
                mkdir -p "${OVL_MNT2}/work"
            fi
        fi
        if [ -n "${OVL_LOOPFILE2}" ]; then
            if [ -z "${OVL_MNT2_SUB}" ]; then
                OVL_MNT2_SUB="${OVL_MNT2}/rw"
            fi
            mkdir -p "${OVL_MNT2_SUB}"
            losetup /dev/loop1 "${OVL_MNT2}/${OVL_LOOPFILE2}"
            mount /dev/loop1 "${OVL_MNT2_SUB}"
            mkdir -p "${OVL_MNT2_SUB}/upper"
            mkdir -p "${OVL_MNT2_SUB}/work"
            UPPER="upperdir=${OVL_MNT2_SUB}/upper"
            WORK="workdir=${OVL_MNT2_SUB}/work"
        else
            if [ -n "${OVL_MNT2_SUB}" ]; then
                    mkdir -p "${OVL_MNT2_SUB}/upper"
                    mkdir -p "${OVL_MNT2_SUB}/work"
                    UPPER="upperdir=${OVL_MNT2_SUB}/upper"
                    WORK="workdir=${OVL_MNT2_SUB}/work"
            fi
        fi
     fi # [ "${OVL_DEV2}" = 'tmpfs' ]
    else # [ -n "${OVL_DEV2}" ]
      if [ -n "${OVL_MNT2_SUB}" ]; then
       mkdir -p "${OVL_MNT2_SUB}/upper"
       mkdir -p "${OVL_MNT2_SUB}/work"
       UPPER="upperdir=${OVL_MNT2_SUB}/upper"
       WORK="workdir=${OVL_MNT2_SUB}/work"
      else
        if [ -z "${UPPER}" ]; then
                UPPER="upperdir=${OVL_MNT1}/upper"
                mkdir -p "${OVL_MNT1}/upper"
        fi
        if [ -z "${WORK}" ]; then
                WORK="workdir=${OVL_MNT1}/work"
                mkdir -p "${OVL_MNT1}/work"
        fi
      fi
    fi # [ -n "${OVL_DEV2}" ]
    good_msg "OverlayFS - lower:${LOWER}, upper:${UPPER}, work:${WORK} ..."
    REAL_ROOTFLAGS="${LOWER},${UPPER},${WORK}"
fi # zm [ "${ROOTFSTYPE}" = 'overlay' ]

------------

# zm 3: move LOOPS_MNT or OVL_MNTs from initramfs to real root
if [ "${MOUNT_MOVE}" = '1' ]; then
        if [ -n "${LOOPS_MNT}" ]; then
                if [ ! -e "${CHROOT}${LOOPS_MNT}" ]; then
                        mkdir -p "${CHROOT}${LOOPS_MNT}"
                fi
                mount --move "${LOOPS_MNT}" "${CHROOT}${LOOPS_MNT}"
                good_msg "Remounting loop_dev=${LOOPS_DEV} to ${CHROOT}${LOOPS_MNT}"
        fi
        if [ -n "${OVL_MNT1}" ]; then
                if [ ! -e "${CHROOT}${OVL_MNT1}" ]; then
                        mkdir -p "${CHROOT}${OVL_MNT1}"
                fi
                mount --move "${OVL_MNT1}" "${CHROOT}${OVL_MNT1}"
                good_msg "Remounting loop_dev=${OVL_DEV1} to ${CHROOT}${OVL_MNT1}"
        fi
        if [ -n "${OVL_MNT2}" ]; then
                if [ ! -e "${CHROOT}${OVL_MNT2}" ]; then
                        mkdir -p "${CHROOT}${OVL_MNT2}"
                fi
        mount --move "${OVL_MNT2}" "${CHROOT}${OVL_MNT2}"
        good_msg "Remounting loop_dev=${OVL_DEV2} to ${CHROOT}${OVL_MNT2}"
        fi
fi # zm

-------

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推 Bencrie: 最近也在玩類似的東西。我發現把 ext4 image 掛起來
→ Bencrie: 沒調過 option 的話效能大概是原生一半左右
我是統一把swap放ssd，tmp,/var/tmp放ram
比較 /在ssd partition, /在loop@ssd, /在loop@hd 感覺差異只有開機時慢1~2秒
其他在上網普通時沒啥差別
以前某web上有說-10%左右
剛剛google "loopback file system performance"
https://serverfault.com/questions/166748/performance-of-loopback-filesystems
它說只有在sync after every write才會慢到-50%
應該把swap,/tmp,/var/tmp移出去 就可以改善很多了
※ 編輯: czm (1.163.141.167), 07/24/2017 17:16:40