Add a formatting container

This is based on the code we used for Docker Editions, and
will format an external drive, to be used for example for
`/var` for Docker image persistence.

It does not `mount` the drive yet, as splitting format and mount
gives better modularity.

Example yaml fragment:
```
  - name: format
    image: "mobylinux/format:097d4f22b20f976b1f89d8f0b8a5d074d35b856c"
    binds:
     - /dev:/dev
    capabilities:
     - CAP_SYS_ADMIN
     - CAP_MKNOD
```

Signed-off-by: Justin Cormack <justin.cormack@docker.com>
This commit is contained in:
Justin Cormack 2017-04-02 15:15:18 +01:00
parent 3223897232
commit 8bcb2c9e0e
3 changed files with 155 additions and 0 deletions

13
pkg/format/Dockerfile Normal file
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FROM alpine:3.5
RUN \
apk update && apk upgrade -a && \
apk add --no-cache \
e2fsprogs \
e2fsprogs-extra \
jq \
sfdisk \
&& true
COPY . ./
CMD ["/bin/sh", "/format.sh"]

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pkg/format/Makefile Normal file
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.PHONY: tag push
BASE=alpine:3.5
IMAGE=format
default: push
hash: Dockerfile format.sh
DOCKER_CONTENT_TRUST=1 docker pull $(BASE)
tar cf - $^ | docker build --no-cache -t $(IMAGE):build -
docker run --rm --entrypoint /bin/sh $(IMAGE):build -c "cat $^ /lib/apk/db/installed | sha1sum" | sed 's/ .*//' > $@
push: hash
docker pull mobylinux/$(IMAGE):$(shell cat hash) || \
(docker tag $(IMAGE):build mobylinux/$(IMAGE):$(shell cat hash) && \
docker push mobylinux/$(IMAGE):$(shell cat hash))
docker rmi $(IMAGE):build
rm -f hash
tag: hash
docker pull mobylinux/$(IMAGE):$(shell cat hash) || \
docker tag $(IMAGE):build mobylinux/$(IMAGE):$(shell cat hash)
docker rmi $(IMAGE):build
rm -f hash
clean:
rm -f hash
.DELETE_ON_ERROR:

113
pkg/format/format.sh Executable file
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#!/bin/sh
# this script assumes anything on the disk can be removed if corrupted
# other use cases may need different scripts.
# currently only supports ext4 but should be expanded
do_fsck()
{
# preen
/sbin/e2fsck -p $*
EXIT_CODE=$?
# exit code 1 is errors corrected
[ "${EXIT_CODE}" -eq 1 ] && EXIT_CODE=0
# exit code 2 or 3 means need to reboot
[ "${EXIT_CODE}" -eq 2 -o "${EXIT_CODE}" -eq 3 ] && /sbin/reboot
# exit code 4 or over is fatal
[ "${EXIT_CODE}" -lt 4 ] && return "${EXIT_CODE}"
# try harder
/sbin/e2fsck -y $*
# exit code 1 is errors corrected
[ "${EXIT_CODE}" -eq 1 ] && EXIT_CODE=0
# exit code 2 or 3 means need to reboot
[ "${EXIT_CODE}" -eq 2 -o "${EXIT_CODE}" -eq 3 ] && /sbin/reboot
# exit code 4 or over is fatal
[ "${EXIT_CODE}" -ge 4 ] && printf "Filesystem unrecoverably corrupted, will reformat\n"
return "${EXIT_CODE}"
}
do_fsck_extend_mount()
{
DRIVE="$1"
DATA="$2"
do_fsck "$DATA" || return 1
# only try to extend if there is a single partition and free space
PARTITIONS=$(sfdisk -J "$DRIVE" | jq '.partitiontable.partitions | length')
if [ "$PARTITIONS" -eq 1 ] && \
sfdisk -F "$DRIVE" | grep -q 'Unpartitioned space' &&
! sfdisk -F "$DRIVE" | grep -q '0 B, 0 bytes, 0 sectors'
then
SPACE=$(sfdisk -F "$DRIVE" | grep 'Unpartitioned space')
printf "Resizing disk partition: $SPACE\n"
START=$(sfdisk -J "$DRIVE" | jq -e '.partitiontable.partitions | map(select(.type=="83")) | .[0].start')
sfdisk -q --delete "$DRIVE" 2> /dev/null
echo "${START},,83;" | sfdisk -q "$DRIVE"
# set bootable flag
sfdisk -A "$DRIVE" 1
# update status
blockdev --rereadpt $diskdev 2> /dev/null
mdev -s
# wait for device
for i in $(seq 1 50); do test -b "$DATA" && break || sleep .1; mdev -s; done
# resize2fs fails unless we use -f here
do_fsck -f "$DATA" || return 1
resize2fs "$DATA"
do_fsck "$DATA" || return 1
fi
}
do_mkfs()
{
diskdev="$1"
# new disks does not have an DOS signature in sector 0
# this makes sfdisk complain. We can workaround this by letting
# fdisk create that DOS signature, by just do a "w", a write.
# http://bugs.alpinelinux.org/issues/145
echo "w" | fdisk $diskdev >/dev/null
# format one large partition
echo ";" | sfdisk --quiet $diskdev
# update status
blockdev --rereadpt $diskdev 2> /dev/null
mdev -s
FSOPTS="-O resize_inode,has_journal,extent,huge_file,flex_bg,uninit_bg,64bit,dir_nlink,extra_isize"
mkfs.ext4 -q -F $FSOPTS ${diskdev}1
}
# TODO fix for multiple disks, cdroms etc
DEV="$(find /dev -maxdepth 1 -type b ! -name 'loop*' | grep -v '[0-9]$' | sed 's@.*/dev/@@' | sort | head -1 )"
[ -z "${DEV}" ] && exit 1
DRIVE="/dev/${DEV}"
# see if it has a partition table already
if sfdisk -d "${DRIVE}" >/dev/null 2>/dev/null
then
DATA=$(sfdisk -J "$DRIVE" | jq -e -r '.partitiontable.partitions | map(select(.type=="83")) | .[0].node')
if [ $? -eq 0 ]
then
do_fsck_extend_mount "$DRIVE" "$DATA" || do_mkfs "$DRIVE"
else
do_mkfs "$DRIVE"
fi
else
do_mkfs "$DRIVE"
fi