During testing of snapd on a stock debian9 install the following issue was found:
The core configure hoook fails with “cannot stat /var/lib/snapd/seccomp: No such file or directory”).
It runs out that inside the core mount namespace (nsenter -m/run/snapd/ns/core.mnt) there is indeed no such file, the /var/lib/snapd/ directory is completely empty.
The /proc/self/mountinfo from inside the namespace:
165 130 7:3 / / rw,relatime - squashfs /dev/loop3 ro 166 165 0:6 / /dev rw,nosuid,relatime master:2 - devtmpfs udev rw,size=738600k,nr_inodes=184650,mode=755 167 166 0:17 / /dev/pts rw,nosuid,noexec,relatime master:3 - devpts devpts rw,gid=5,mode=620,ptmxmode=000 168 166 0:19 / /dev/shm rw,nosuid,nodev master:4 - tmpfs tmpfs rw 169 166 0:14 / /dev/mqueue rw,relatime master:23 - mqueue mqueue rw 170 166 0:34 / /dev/hugepages rw,relatime master:24 - hugetlbfs hugetlbfs rw 171 165 8:1 /etc /etc rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 172 165 8:1 /home /home rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 173 165 8:1 /root /root rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 174 165 0:4 / /proc rw,nosuid,nodev,noexec,relatime master:12 - proc proc rw 175 174 0:33 / /proc/sys/fs/binfmt_misc rw,relatime master:22 - autofs systemd-1 rw,fd=35,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=8916 176 165 0:16 / /sys rw,nosuid,nodev,noexec,relatime master:7 - sysfs sysfs rw 177 176 0:15 / /sys/kernel/security rw,nosuid,nodev,noexec,relatime master:8 - securityfs securityfs rw 178 176 0:21 / /sys/fs/cgroup ro,nosuid,nodev,noexec master:9 - tmpfs tmpfs ro,mode=755 179 178 0:22 / /sys/fs/cgroup/systemd rw,nosuid,nodev,noexec,relatime master:10 - cgroup cgroup rw,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd 180 178 0:24 / /sys/fs/cgroup/pids rw,nosuid,nodev,noexec,relatime master:13 - cgroup cgroup rw,pids 181 178 0:25 / /sys/fs/cgroup/freezer rw,nosuid,nodev,noexec,relatime master:14 - cgroup cgroup rw,freezer 182 178 0:26 / /sys/fs/cgroup/memory rw,nosuid,nodev,noexec,relatime master:15 - cgroup cgroup rw,memory 183 178 0:27 / /sys/fs/cgroup/cpu,cpuacct rw,nosuid,nodev,noexec,relatime master:16 - cgroup cgroup rw,cpu,cpuacct 184 178 0:28 / /sys/fs/cgroup/net_cls,net_prio rw,nosuid,nodev,noexec,relatime master:17 - cgroup cgroup rw,net_cls,net_prio 185 178 0:29 / /sys/fs/cgroup/blkio rw,nosuid,nodev,noexec,relatime master:18 - cgroup cgroup rw,blkio 186 178 0:30 / /sys/fs/cgroup/devices rw,nosuid,nodev,noexec,relatime master:19 - cgroup cgroup rw,devices 187 178 0:31 / /sys/fs/cgroup/cpuset rw,nosuid,nodev,noexec,relatime master:20 - cgroup cgroup rw,cpuset 188 178 0:32 / /sys/fs/cgroup/perf_event rw,nosuid,nodev,noexec,relatime master:21 - cgroup cgroup rw,perf_event 189 176 0:23 / /sys/fs/pstore rw,nosuid,nodev,noexec,relatime master:11 - pstore pstore rw 190 176 0:7 / /sys/kernel/debug rw,relatime master:25 - debugfs debugfs rw 191 165 8:1 /tmp /tmp rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 192 165 8:1 /var/snap//deleted /var/snap rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 193 135 8:1 /var/lib/snapd//deleted /var/lib/snapd rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 194 165 8:1 /var/tmp /var/tmp rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 195 165 0:18 / /run rw,nosuid,noexec,relatime master:5 - tmpfs tmpfs rw,size=149956k,mode=755 196 195 0:20 / /run/lock rw,nosuid,nodev,noexec,relatime master:6 - tmpfs tmpfs rw,size=5120k 197 195 0:18 /snapd/ns /run/snapd/ns rw,nosuid,noexec,relatime - tmpfs tmpfs rw,size=149956k,mode=755 198 165 8:1 /lib/modules /lib/modules rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 199 165 8:1 /usr/src /usr/src rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 200 165 8:1 /var/log /var/log rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 201 165 8:1 /media /media rw,relatime shared:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 202 195 0:18 /netns /run/netns rw,nosuid,noexec,relatime shared:5 - tmpfs tmpfs rw,size=149956k,mode=755 203 171 7:3 /etc/alternatives /etc/alternatives rw,relatime - squashfs /dev/loop3 ro 204 165 8:1 /snap//deleted /snap rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 132 191 8:1 /tmp/snap.0_snap.core.hook.configure_XhtHU0/tmp /tmp rw,relatime - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 133 167 0:37 / /dev/pts rw,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=666 134 166 0:37 /ptmx /dev/ptmx rw,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=666 135 165 0:38 / /var/lib rw,nosuid,nodev,relatime - tmpfs none rw 136 135 7:3 /var/lib/apparmor /var/lib/apparmor rw,relatime - squashfs /dev/loop3 ro 140 135 7:3 /var/lib/classic /var/lib/classic rw,relatime - squashfs /dev/loop3 ro 141 135 7:3 /var/lib/cloud /var/lib/cloud rw,relatime - squashfs /dev/loop3 ro 142 135 7:3 /var/lib/console-conf /var/lib/console-conf rw,relatime - squashfs /dev/loop3 ro 143 135 7:3 /var/lib/dbus /var/lib/dbus rw,relatime - squashfs /dev/loop3 ro 144 135 7:3 /var/lib/dhcp /var/lib/dhcp rw,relatime - squashfs /dev/loop3 ro 145 135 7:3 /var/lib/extrausers /var/lib/extrausers rw,relatime - squashfs /dev/loop3 ro 146 135 7:3 /var/lib/initramfs-tools /var/lib/initramfs-tools rw,relatime - squashfs /dev/loop3 ro 147 135 7:3 /var/lib/initscripts /var/lib/initscripts rw,relatime - squashfs /dev/loop3 ro 148 135 7:3 /var/lib/insserv /var/lib/insserv rw,relatime - squashfs /dev/loop3 ro 149 135 7:3 /var/lib/logrotate /var/lib/logrotate rw,relatime - squashfs /dev/loop3 ro 150 135 7:3 /var/lib/machines /var/lib/machines rw,relatime - squashfs /dev/loop3 ro 151 135 7:3 /var/lib/misc /var/lib/misc rw,relatime - squashfs /dev/loop3 ro 152 135 7:3 /var/lib/pam /var/lib/pam rw,relatime - squashfs /dev/loop3 ro 153 135 7:3 /var/lib/python /var/lib/python rw,relatime - squashfs /dev/loop3 ro 154 135 7:3 /var/lib/resolvconf /var/lib/resolvconf rw,relatime - squashfs /dev/loop3 ro 156 135 7:3 /var/lib/sudo /var/lib/sudo rw,relatime - squashfs /dev/loop3 ro 161 135 7:3 /var/lib/systemd /var/lib/systemd rw,relatime - squashfs /dev/loop3 ro 162 135 7:3 /var/lib/ubuntu-fan /var/lib/ubuntu-fan rw,relatime - squashfs /dev/loop3 ro 163 135 7:3 /var/lib/ucf /var/lib/ucf rw,relatime - squashfs /dev/loop3 ro 164 135 7:3 /var/lib/update-rc.d /var/lib/update-rc.d rw,relatime - squashfs /dev/loop3 ro 210 135 7:3 /var/lib/urandom /var/lib/urandom rw,relatime - squashfs /dev/loop3 ro 211 135 7:3 /var/lib/vim /var/lib/vim rw,relatime - squashfs /dev/loop3 ro 212 135 7:3 /var/lib/waagent /var/lib/waagent rw,relatime - squashfs /dev/loop3 ro 248 176 0:39 / /sys/fs/fuse/connections rw,relatime master:83 - fusectl fusectl rw
The same from outside the namespace:
16 21 0:16 / /sys rw,nosuid,nodev,noexec,relatime shared:7 - sysfs sysfs rw 17 21 0:4 / /proc rw,nosuid,nodev,noexec,relatime shared:12 - proc proc rw 18 21 0:6 / /dev rw,nosuid,relatime shared:2 - devtmpfs udev rw,size=738600k,nr_inodes=184650,mode=755 19 18 0:17 / /dev/pts rw,nosuid,noexec,relatime shared:3 - devpts devpts rw,gid=5,mode=620,ptmxmode=000 20 21 0:18 / /run rw,nosuid,noexec,relatime shared:5 - tmpfs tmpfs rw,size=149956k,mode=755 21 0 8:1 / / rw,relatime shared:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered 22 16 0:15 / /sys/kernel/security rw,nosuid,nodev,noexec,relatime shared:8 - securityfs securityfs rw 23 18 0:19 / /dev/shm rw,nosuid,nodev shared:4 - tmpfs tmpfs rw 24 20 0:20 / /run/lock rw,nosuid,nodev,noexec,relatime shared:6 - tmpfs tmpfs rw,size=5120k 25 16 0:21 / /sys/fs/cgroup ro,nosuid,nodev,noexec shared:9 - tmpfs tmpfs ro,mode=755 26 25 0:22 / /sys/fs/cgroup/systemd rw,nosuid,nodev,noexec,relatime shared:10 - cgroup cgroup rw,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd 27 16 0:23 / /sys/fs/pstore rw,nosuid,nodev,noexec,relatime shared:11 - pstore pstore rw 28 25 0:24 / /sys/fs/cgroup/pids rw,nosuid,nodev,noexec,relatime shared:13 - cgroup cgroup rw,pids 29 25 0:25 / /sys/fs/cgroup/freezer rw,nosuid,nodev,noexec,relatime shared:14 - cgroup cgroup rw,freezer 30 25 0:26 / /sys/fs/cgroup/memory rw,nosuid,nodev,noexec,relatime shared:15 - cgroup cgroup rw,memory 31 25 0:27 / /sys/fs/cgroup/cpu,cpuacct rw,nosuid,nodev,noexec,relatime shared:16 - cgroup cgroup rw,cpu,cpuacct 32 25 0:28 / /sys/fs/cgroup/net_cls,net_prio rw,nosuid,nodev,noexec,relatime shared:17 - cgroup cgroup rw,net_cls,net_prio 33 25 0:29 / /sys/fs/cgroup/blkio rw,nosuid,nodev,noexec,relatime shared:18 - cgroup cgroup rw,blkio 34 25 0:30 / /sys/fs/cgroup/devices rw,nosuid,nodev,noexec,relatime shared:19 - cgroup cgroup rw,devices 35 25 0:31 / /sys/fs/cgroup/cpuset rw,nosuid,nodev,noexec,relatime shared:20 - cgroup cgroup rw,cpuset 36 25 0:32 / /sys/fs/cgroup/perf_event rw,nosuid,nodev,noexec,relatime shared:21 - cgroup cgroup rw,perf_event 37 17 0:33 / /proc/sys/fs/binfmt_misc rw,relatime shared:22 - autofs systemd-1 rw,fd=35,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=8916 38 18 0:14 / /dev/mqueue rw,relatime shared:23 - mqueue mqueue rw 39 18 0:34 / /dev/hugepages rw,relatime shared:24 - hugetlbfs hugetlbfs rw 40 16 0:7 / /sys/kernel/debug rw,relatime shared:25 - debugfs debugfs rw 127 20 0:18 /snapd/ns /run/snapd/ns rw,nosuid,noexec,relatime shared:81 - tmpfs tmpfs rw,size=149956k,mode=755 155 127 0:3 mnt:[4026532096] /run/snapd/ns/core.mnt rw shared:82 - nsfs nsfs rw 244 16 0:39 / /sys/fs/fuse/connections rw,relatime shared:83 - fusectl fusectl rw 98 127 0:18 /snapd/ns /run/snapd/ns rw,nosuid,noexec,relatime - tmpfs tmpfs rw,size=149956k,mode=755 115 98 0:3 mnt:[4026532096] /run/snapd/ns/core.mnt rw shared:82 - nsfs nsfs rw 95 21 7:0 / /snap/core/2488 rw,relatime shared:57 - squashfs /dev/loop0 ro
Note the 192 165 8:1 /var/snap//deleted /var/snap rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered line.
This is kernel 4.9.0-1-amd64.