It seems that if you want to have mdadm installed but not present in the
initramfs then the only option is to remove the mdadm files from under
/usr/share/initramfs-tools. Otherwise you get a larger initramfs and some
delay while it tries to assemble a mdadm that may not be possible.
Here are some situations where you want mdadm installed but not in the
initramfs:
Making a recovery disk that needs to be able to access raid etc but not for
booting.
Running a system that has /boot on software RAID and / on some other form of
RAID (such as BTRFS or ZFS). Especially if that system has VMs that use
the same initramfs and have no software RAID because they have virtual devices
from BTRFS or ZFS filesystems.
Running a system with limited disk that needs to connect to arrays
occasionally, such as using a laptop with a single internal disk to connect to
RAID arrays and test them.
--- /etc/default/mdadm
AUTOCHECK=true
START_DAEMON=true
DAEMON_OPTIONS="--syslog"
VERBOSE=false
487104 blocks super 1.2 [2/2] [UU]
bitmap: 0/1 pages [0KB], 65536KB chunk
unused devices: <none>
--- /proc/partitions:
major minor #blocks name
8 16 117220824 sdb
8 17 487424 sdb1
8 18 116732376 sdb2
8 32 234431064 sdc
8 33 487424 sdc1
8 34 233942616 sdc2
8 0 468851544 sda
8 1 487424 sda1
8 2 468363096 sda2
9 0 487104 md0
7 0 2097152 loop0
7 2 253952 loop2
--- LVM physical volumes:
LVM does not seem to be used.
--- mount output
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime,seclabel)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,nosuid,relatime,seclabel,size=8186296k,nr_inodes=2046574,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,seclabel,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,noexec,relatime,seclabel,size=1639584k,mode=755)
/dev/sdc2 on / type btrfs (rw,relatime,seclabel,ssd,space_cache,skip_balance,subvolid=5,subvol=/)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,seclabel)
tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,seclabel,size=5120k)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,seclabel,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime,seclabel)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=14789)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,seclabel)
debugfs on /sys/kernel/debug type debugfs (rw,relatime,seclabel)
mqueue on /dev/mqueue type mqueue (rw,relatime,seclabel)
sunrpc on /run/rpc_pipefs type rpc_pipefs (rw,relatime)
nfsd on /proc/fs/nfsd type nfsd (rw,relatime)
/dev/md0 on /boot type ext4 (rw,nodev,noexec,noatime,seclabel,data=ordered)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,seclabel,size=1639580k,mode=700)
/xenstore/isos/debian-8.7.1-amd64-netinst.iso on /mnt/tmp2 type iso9660 (ro,relatime)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
--- initrd.img-4.9.0-2-amd64:
28318 blocks
d3be82c0f275d6c25b04d388baf9e836 ./etc/modprobe.d/mdadm.conf
74e5bb9fd80508594e8a702375fcc243 ./lib/modules/4.9.0-2-amd64/kernel/drivers/md/dm-mod.ko
--- initrd's /conf/conf.d/md:
no conf/md file.
--- /proc/modules:
dm_mod 118784 0 - Live 0xffffffffc0a1a000
raid10 49152 0 - Live 0xffffffffc0344000
raid456 106496 0 - Live 0xffffffffc041e000
async_raid6_recov 20480 1 raid456, Live 0xffffffffc02e0000
async_memcpy 16384 2 raid456,async_raid6_recov, Live 0xffffffffc02db000
async_pq 16384 2 raid456,async_raid6_recov, Live 0xffffffffc0293000
async_xor 16384 3 raid456,async_raid6_recov,async_pq, Live 0xffffffffc028e000
async_tx 16384 5 raid456,async_raid6_recov,async_memcpy,async_pq,async_xor, Live 0xffffffffc0289000
raid6_pq 110592 4 btrfs,raid456,async_raid6_recov,async_pq, Live 0xffffffffc03e0000
libcrc32c 16384 2 xfs,raid456, Live 0xffffffffc0271000
raid0 20480 0 - Live 0xffffffffc022e000
multipath 16384 0 - Live 0xffffffffc0229000
linear 16384 0 - Live 0xffffffffc01df000
raid1 36864 1 - Live 0xffffffffc0216000
md_mod 131072 7 raid10,raid456,raid0,multipath,linear,raid1, Live 0xffffffffc03bf000
--- /var/log/syslog:
--- volume detail:
/dev/sda:
MBR Magic : aa55
Partition[0] : 974848 sectors at 2048 (type fd)
Partition[1] : 936726192 sectors at 976896 (type 83)
--
/dev/sda1:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : 5d63e73c:6c6845cf:9ed639c1:ba2f50af
Name : othello2:0
Creation Time : Wed Apr 16 19:34:29 2014
Raid Level : raid1
Raid Devices : 2
Avail Dev Size : 974336 (475.75 MiB 498.86 MB)
Array Size : 487104 (475.69 MiB 498.79 MB)
Used Dev Size : 974208 (475.69 MiB 498.79 MB)
Data Offset : 512 sectors
Super Offset : 8 sectors
Unused Space : before=424 sectors, after=128 sectors
State : clean
Device UUID : 33022856:08f926d4:e69e2826:cf26d3dd
Internal Bitmap : 8 sectors from superblock
Update Time : Mon Apr 17 18:28:25 2017
Bad Block Log : 512 entries available at offset 72 sectors
Checksum : 982e7e37 - correct
Events : 415
Device Role : Active device 0
Array State : AA ('A' == active, '.' == missing, 'R' == replacing)
--
/dev/sda2 is not recognised by mdadm.
/dev/sdb:
MBR Magic : aa55
Partition[0] : 974848 sectors at 2048 (type fd)
Partition[1] : 233464752 sectors at 976896 (type 83)
--
/dev/sdb1:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : 5d63e73c:6c6845cf:9ed639c1:ba2f50af
Name : othello2:0
Creation Time : Wed Apr 16 19:34:29 2014
Raid Level : raid1
Raid Devices : 2
Avail Dev Size : 974336 (475.75 MiB 498.86 MB)
Array Size : 487104 (475.69 MiB 498.79 MB)
Used Dev Size : 974208 (475.69 MiB 498.79 MB)
Data Offset : 512 sectors
Super Offset : 8 sectors
Unused Space : before=424 sectors, after=128 sectors
State : clean
Device UUID : 492a9016:28c29246:fa48424b:2b133f0b
Internal Bitmap : 8 sectors from superblock
Update Time : Tue Mar 7 15:00:04 2017
Bad Block Log : 512 entries available at offset 72 sectors
Checksum : 1d51b95a - correct
Events : 387
Device Role : Active device 1
Array State : AA ('A' == active, '.' == missing, 'R' == replacing)
--
/dev/sdb2 is not recognised by mdadm.
/dev/sdc:
MBR Magic : aa55
Partition[0] : 974848 sectors at 2048 (type fd)
Partition[1] : 467885232 sectors at 976896 (type 83)
--
/dev/sdc1:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : 5d63e73c:6c6845cf:9ed639c1:ba2f50af
Name : othello2:0
Creation Time : Wed Apr 16 19:34:29 2014
Raid Level : raid1
Raid Devices : 2
Avail Dev Size : 974336 (475.75 MiB 498.86 MB)
Array Size : 487104 (475.69 MiB 498.79 MB)
Used Dev Size : 974208 (475.69 MiB 498.79 MB)
Data Offset : 512 sectors
Super Offset : 8 sectors
Unused Space : before=424 sectors, after=128 sectors
State : clean
Device UUID : daf71a6f:892080f9:0421ca74:086e2786
Internal Bitmap : 8 sectors from superblock
Update Time : Mon Apr 17 18:28:25 2017
Bad Block Log : 512 entries available at offset 72 sectors
Checksum : cd7064b5 - correct
Events : 415
Device Role : Active device 1
Array State : AA ('A' == active, '.' == missing, 'R' == replacing)
--
/dev/sdc2 is not recognised by mdadm.
--- /proc/cmdline
BOOT_IMAGE=/vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance selinux=1 security=selinux
--- grub2:
set root='hd2,msdos2'
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux init=/lib/sysvinit/init
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro single init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-1-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-1-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux init=/lib/sysvinit/init
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-1-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro single init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux init=/lib/sysvinit/init
menuentry 'Debian GNU/Linux, with Linux 4.9.0-2-amd64 (recovery mode) (on /dev/sda2)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/vmlinuz-4.9.0-2-amd64-root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro single init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux-caf5f13b-c48f-4d01-aa30-93d29be10c03' {
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-2-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro single init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-1-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-1-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux init=/lib/sysvinit/init
menuentry 'Debian GNU/Linux, with Linux 4.9.0-1-amd64 (recovery mode) (on /dev/sda2)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/vmlinuz-4.9.0-1-amd64-root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro single init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux-caf5f13b-c48f-4d01-aa30-93d29be10c03' {
set root='mduuid/5d63e73c6c6845cf9ed639c1ba2f50af'
linux /vmlinuz-4.9.0-1-amd64 root=UUID=caf5f13b-c48f-4d01-aa30-93d29be10c03 ro single init=/bin/systemd consoleblank=0 rootflags=skip_balance security=selinux
--- udev:
ii udev 232-22 amd64 /dev/ and hotplug management daem
aa83f41de49462d05e446cfc5e14e74b /lib/udev/rules.d/63-md-raid-arrays.rules
5de7d0b70cd948d00bb38ca75ad5f288 /lib/udev/rules.d/64-md-raid-assembly.rules
8e28181624da2ed60739cae470ca6415 /lib/udev/rules.d/99-systemd.rules
--- /dev:
brw-rw----. 1 root disk 9, 0 Mar 27 03:15 /dev/md0
/dev/disk/by-id:
total 0
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 ata-INTEL_SSDSC2CT120A3_CVMP219105MT120BGN -> ../../sdb
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 ata-INTEL_SSDSC2CT120A3_CVMP219105MT120BGN-part1 -> ../../sdb1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 ata-INTEL_SSDSC2CT120A3_CVMP219105MT120BGN-part2 -> ../../sdb2
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 ata-INTEL_SSDSCKKW480H6_CVLY619500AV480F -> ../../sda
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 ata-INTEL_SSDSCKKW480H6_CVLY619500AV480F-part1 -> ../../sda1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 ata-INTEL_SSDSCKKW480H6_CVLY619500AV480F-part2 -> ../../sda2
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 ata-SanDisk_SDSSDA240G_164056457915 -> ../../sdc
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 ata-SanDisk_SDSSDA240G_164056457915-part1 -> ../../sdc1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 ata-SanDisk_SDSSDA240G_164056457915-part2 -> ../../sdc2
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 md-name-othello2:0 -> ../../md0
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 md-uuid-5d63e73c:6c6845cf:9ed639c1:ba2f50af -> ../../md0
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 wwn-0x5001517bb291304b -> ../../sdb
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 wwn-0x5001517bb291304b-part1 -> ../../sdb1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 wwn-0x5001517bb291304b-part2 -> ../../sdb2
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 wwn-0x5001b444a66e657a -> ../../sdc
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 wwn-0x5001b444a66e657a-part1 -> ../../sdc1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 wwn-0x5001b444a66e657a-part2 -> ../../sdc2
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 wwn-0x55cd2e414cbf9788 -> ../../sda
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 wwn-0x55cd2e414cbf9788-part1 -> ../../sda1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 wwn-0x55cd2e414cbf9788-part2 -> ../../sda2
/dev/disk/by-label:
total 0
lrwxrwxrwx. 1 root root 11 Apr 17 14:23 Debian\x208.7.1\x20amd64\x201 -> ../../loop2
/dev/disk/by-partuuid:
total 0
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 00095041-01 -> ../../sda1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 00095041-02 -> ../../sda2
/dev/disk/by-path:
total 0
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 pci-0000:00:1f.2-ata-1 -> ../../sdb
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 pci-0000:00:1f.2-ata-1-part1 -> ../../sda1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 pci-0000:00:1f.2-ata-1-part2 -> ../../sda2
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 pci-0000:00:1f.2-ata-2 -> ../../sdc
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 pci-0000:00:1f.2-ata-2-part1 -> ../../sdc1
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 pci-0000:00:1f.2-ata-2-part2 -> ../../sdc2
/dev/disk/by-uuid:
total 0
lrwxrwxrwx. 1 root root 9 Mar 27 03:15 1fc41a68-3a3b-4e02-ba0d-a26d80478336 -> ../../md0
lrwxrwxrwx. 1 root root 11 Apr 17 14:23 2017-01-16-11-01-01-00 -> ../../loop2
lrwxrwxrwx. 1 root root 11 Mar 27 03:15 3692132f-0122-46d5-ac32-d5cf0cfa28a8 -> ../../loop0
lrwxrwxrwx. 1 root root 10 Mar 27 03:15 caf5f13b-c48f-4d01-aa30-93d29be10c03 -> ../../sda2
/dev/md:
total 0
lrwxrwxrwx. 1 root root 6 Mar 27 03:15 0 -> ../md0
Auto-generated on Mon, 17 Apr 2017 18:30:37 +1000 by mdadm bugscript