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#!/bin/bash
#
# Function to identify write-protected disks and partitions.
function is_write_protected() {
local given_device="$1"
# Provided a matching device node exists for the given device
# return 0 when the given device is write-protected by ID
# or when it is write-protected by file system label
# otherwise return 1 (i.e. when it is not write-protected).
# For example /sys/block/sda has matching device node /dev/sda
# and /sys/block/nvme0n1 has matching device node /dev/nvme0n1
# but not all /sys/block/* entries have a matching device node
# in particular /sys/block/nvme0c0n1 has no /dev/nvme0c0n1 because it is part of NVMe multipathing
# see https://github.com/rear/rear/issues/3085
# When both WRITE_PROTECTED_IDS and WRITE_PROTECTED_FS_LABEL_PATTERNS are empty
# no device is write-protected:
if (( ${#WRITE_PROTECTED_IDS[@]} )) || (( ${#WRITE_PROTECTED_FS_LABEL_PATTERNS[@]} )) ; then
Log "Checking write protection for '$given_device'"
else
Log "'$given_device' is not write-protected (empty WRITE_PROTECTED_IDS and WRITE_PROTECTED_FS_LABEL_PATTERNS)"
return 1
fi
# Determine the matching device node, translate it if given as /sys/block/*
# But $device_node could be also symlink to the actual device node, for example
# for OUTPUT=USB $given_device is of the form /dev/disk/by-label/$USB_DEVICE_FILESYSTEM_LABEL
# which is a symlink to the ReaR data partition (e.g. /dev/sdb3 on a USB disk /dev/sdb).
local device_node="$given_device"
[[ "$given_device" == /sys/block/* ]] && device_node="$( get_device_name "$given_device" )"
# Because this is meant to identify write-protected disks and partitions
# only given devices with a matching device node are considered for write protection
# so given devices without matching device node get reported as not write protected:
if test -e "$device_node" ; then
test -b "$device_node" || BugError "is_write_protected called for '$given_device' but '$device_node' is no block device"
else
Log "'$given_device' is not write-protected ('$device_node' does not exist)"
return 1
fi
# The matching device node exists and is a block device
# so given_device and device_node are non empty words.
# Determine the IDs of the disk device that belongs to the given device:
# At least for OUTPUT=USB $given_device is of the form /dev/disk/by-label/$USB_DEVICE_FILESYSTEM_LABEL
# which is a symlink to the ReaR data partition (e.g. /dev/sdb3 on a USB disk /dev/sdb).
# On a USB disk that was formatted with "rear format" there is only one layer of child devices
# (i.e. there are only partitions like /dev/sdb1 /dev/sdb2 /dev/sdb3 on a USB disk /dev/sdb).
# So we only need to use the direct parent device to get all IDs of the whole disk
# because the goal is to write-protect the whole disk by using all its IDs
# cf. https://github.com/rear/rear/pull/2703#issuecomment-952888484
local parent_device=""
# Older Linux distributions do not contain lsblk (e.g. SLES10)
# and older lsblk versions do not support the output column PKNAME
# e.g. lsblk in util-linux 2.19.1 in SLES11 supports NAME and KNAME but not PKNAME
# cf. https://github.com/rear/rear/pull/2626#issuecomment-856700823
# We ignore lsblk failures and error messages and we skip empty lines in the output via 'awk NF'
# cf. https://unix.stackexchange.com/questions/274708/most-elegant-pipe-to-get-rid-of-empty-lines-you-can-think-of
# and https://stackoverflow.com/questions/23544804/how-awk-nf-filename-is-working
# (an empty line appears for a whole disk device e.g. /dev/sdb that has no PKNAME)
# and we use only the topmost reported PKNAME:
parent_device="$( lsblk -inpo PKNAME "$device_node" 2>/dev/null | awk NF | head -n1 )"
# parent_device is empty when lsblk does not support PKNAME.
# In this case use device_node as fallback for parent_device.
# Without quoting an empty parent_device would result plain "test -b" which would (falsely) succeed:
test -b "$parent_device" || parent_device="$device_node"
# The default WRITE_PROTECTED_ID_TYPES are UUID PTUUID PARTUUID WWN.
# Older lsblk versions do not support all output columns UUID PTUUID PARTUUID WWN
# e.g. lsblk in util-linux 2.19.1 in SLES11 only supports UUID but neither PTUUID nor PARTUUID nor WWN
# cf. https://github.com/rear/rear/pull/2626#issuecomment-856700823
# When an unsupported output column is specified lsblk aborts with "unknown column" error message
# without output for supported output columns so we run lsblk for each output column separately
# and ignore lsblk failures and error messages and we skip empty lines in the output via 'awk NF'
# (empty lines appear when a partition does not have a filesystem UUID or for the whole device that has no PARTUUID
# or for all columns except UUID when a child device is a /dev/mapper/* device
# and some devices do not have any WWN set)
# and we remove duplicate reported IDs (in particular PTUUID is reported also for each partition):
local ids column
ids="$( for column in $WRITE_PROTECTED_ID_TYPES ; do lsblk -ino $column "$parent_device" 2>/dev/null ; done | awk NF | sort -u )"
# Determine if it is write-protected by ID
# i.e. return 0 if one of the device IDs is in the list of write-protected IDs.
local id
# ids is a string of IDs separated by newline characters
if test "$ids" ; then
for id in $ids ; do
if IsInArray "$id" "${WRITE_PROTECTED_IDS[@]}" ; then
Log "$given_device is designated as write-protected by ID '$id'"
return 0
fi
done
Log "$given_device is not write-protected by ID"
else
LogPrintError "Cannot check write protection by ID for $given_device (no ID found)"
# It would be safer to assume a disk without ID is protected (and return 0)
# instead of assuming that it is not protected and proceed.
# But in practice that does not work sufficiently well because it can happen
# that a disk has no ID (by default non of UUID PTUUID PARTUUID WWN)
# which usually means there is nothing on the disk so that empty disks
# would get excluded as write-protected from being used to recreate the system
# cf. https://github.com/rear/rear/pull/2703#discussion_r757393547
# By default we write protect ReaR's own disk where the recovery system is and
# we assume it cannot happen that this disk has none of UUID PTUUID PARTUUID WWN
# so it should be safe to assume a disk without UUID PTUUID PARTUUID WWN is empty
# and meant to be used to recreate the system so it should not be write-protected by ID.
fi
# Determine if it is write-protected by file system labels
# i.e. return 0 if one of the device file system labels
# matches one of the WRITE_PROTECTED_FS_LABEL_PATTERNS.
# lsblk in util-linux 2.19.1 in SLES11 supports '-ino LABEL'
# cf. https://github.com/rear/rear/pull/2626#issuecomment-856700823
local device_label fs_label_pattern
while read -r device_label ; do
test "$device_label" || continue
for fs_label_pattern in "${WRITE_PROTECTED_FS_LABEL_PATTERNS[@]}" ; do
if [[ "$device_label" == $fs_label_pattern ]] ; then
Log "$given_device is designated as write-protected (its label '$device_label' matches '$fs_label_pattern')"
return 0
fi
done
done < <( lsblk -ino LABEL "$device_node" )
Log "$given_device is not write-protected by file system label"
# The given device is neither write-protected by ID
# nor is it write-protected by file system label:
Log "$given_device is not write-protected"
return 1
}