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Diffstat (limited to 'src/script/run_uml.sh')
| -rwxr-xr-x | src/script/run_uml.sh | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/src/script/run_uml.sh b/src/script/run_uml.sh new file mode 100755 index 000000000..9bff38b22 --- /dev/null +++ b/src/script/run_uml.sh @@ -0,0 +1,212 @@ +#!/bin/bash -norc + +# Magic startup script for a UML instance. As long as unique +# instances are started, more than one of them can be concurrently +# in use on a single system. All their network interfaces are +# bridged together onto the virtual bridge "virbr0" which is +# supplied by the "libvirt" package. +# +# Note that a DHCP server is started for that interface. It's +# configured in this file: +# /etc/libvirt/qemu/networks/default.xml +# Unfortunately what I see there serves all possible DHCP addresses, +# so stealing them like we do here isn't really kosher. To fix +# it, that configuration should change to serve a smaller subset +# of the available address range. +# +# Each instance uses its own tun/tap device, created using the +# "tunctl" command. The assigned tap device will correspond with +# the guest id (a small integer representing the instance), i.e., +# guest id 1 uses tap1, etc. The tap device is attached to the +# virtual bridge, which will have its own subnet associated with it. +# The guest side of that interface will have the same subnet as the +# bridge interface, with the bottom bits representing (normally) 100 +# more than the guest id. So for subnet 192.168.122.0/24, guest +# id 1 will use ip 192.168.122.101, guest id 2 will use ip +# 192.168.122.102, and so on. Because these interfaces are bridged, +# they can all communicate with each other. + +# You will want to override this by setting and exporting the +# "CEPH_TOP" environment variable to be the directory that contains +# the "ceph-client" source tree. +CEPH_TOP="${CEPH_TOP:-/home/elder/ceph}" + +# You may want to change this too, if you want guest UML instances +# to have a diffeerent IP address range. The guest IP will be based +# on this plus GUEST_ID (defined below). +GUEST_IP_OFFSET="${GUEST_IP_OFFSET:-100}" + +############################# + +if [ $# -gt 1 ]; then + echo "" >&2 + echo "Usage: $(basename $0) [guest_id]" >&2 + echo "" >&2 + echo " guest_id is a small integer (default 1)" >&2 + echo " (each UML instance needs a distinct guest_id)" >&2 + echo "" >&2 + exit 1 +elif [ $# -eq 1 ]; then + GUEST_ID="$1" +else + GUEST_ID=1 +fi + +# This will be what the guest host calls itself. +GUEST_HOSTNAME="uml-${GUEST_ID}" + +# This is the path to the boot disk image used by UML. +DISK_IMAGE_A="${CEPH_TOP}/ceph-client/uml.${GUEST_ID}" +if [ ! -f "${DISK_IMAGE_A}" ]; then + echo "root disk image not found (or not a file)" >&2 + exit 2 +fi + +# Hostid 1 uses tun/tap device tap1, hostid 2 uses tap2, etc. +TAP_ID="${GUEST_ID}" +# This is the tap device used for this UML instance +TAP="tap${TAP_ID}" + +# This is just used to mount an image temporarily +TMP_MNT="/tmp/m$$" + +# Where to put a config file generated for this tap device +TAP_IFUPDOWN_CONFIG="/tmp/interface-${TAP}" + +# Compute the HOST_IP and BROADCAST address values to use, +# and assign shell variables with those names to their values. +# Also compute BITS, which is the network prefix length used. +# The NETMASK is then computed using that BITS value. +eval $( +ip addr show virbr0 | awk ' +/inet/ { + split($2, a, "/") + printf("HOST_IP=%s\n", a[1]); + printf("BROADCAST=%s\n", $4); + printf("BITS=%s\n", a[2]); + exit(0); +}') + +# Use bc to avoid 32-bit wrap when computing netmask +eval $( +echo -n "NETMASK=" +bc <<! | fmt | sed 's/ /./g' +m = 2 ^ 32 - 2 ^ (32 - ${BITS}) +for (p = 24; p >= 0; p = p - 8) + m / (2 ^ p) % 256 +! +) + +# Now use the netmask and the host IP to compute the subnet address +# and from that the guest IP address to use. +eval $( +awk ' +function from_quad(addr, a, val, i) { + if (split(addr, a, ".") != 4) + exit(1); # address not in dotted quad format + val = 0; + for (i = 1; i <= 4; i++) + val = val * 256 + a[i]; + return val; +} +function to_quad(val, addr, i) { + addr = ""; + for (i = 1; i <= 4; i++) { + addr = sprintf("%u%s%s", val % 256, i > 1 ? "." : "", addr); + val = int(val / 256); + } + if ((val + 0) != 0) + exit(1); # value provided exceeded 32 bits + return addr; +} +BEGIN { + host_ip = from_quad("'${HOST_IP}'"); + netmask = from_quad("'${NETMASK}'"); + guest_net_ip = '${GUEST_IP_OFFSET}' + '${GUEST_ID}'; + if (and(netmask, guest_net_ip)) + exit(1); # address too big for subnet + subnet = and(host_ip, netmask); + guest_ip = or(subnet, guest_net_ip); + if (guest_ip == host_ip) + exit(1); # computed guest ip matches host ip + + printf("SUBNET=%s\n", to_quad(subnet)); + printf("GUEST_IP=%s\n", to_quad(guest_ip)); +} +' < /dev/null +) + +############## OK, we now know all our network parameters... + +# There is a series of things that need to be done as superuser, +# so group them all into one big (and sort of nested!) sudo request. +sudo -s <<EnD_Of_sUdO +# Mount the boot disk for the UML and set up some configuration +# files there. +mkdir -p "${TMP_MNT}" +mount -o loop "${DISK_IMAGE_A}" "${TMP_MNT}" + +# Arrange for loopback and eth0 to load automatically, +# and for eth0 to have our desired network parameters. +cat > "${TMP_MNT}/etc/network/interfaces" <<! +# Used by ifup(8) and ifdown(8). See the interfaces(5) manpage or +# /usr/share/doc/ifupdown/examples for more information. +auto lo +iface lo inet loopback +auto eth0 +# iface eth0 inet dhcp +iface eth0 inet static + address ${GUEST_IP} + netmask ${NETMASK} + broadcast ${BROADCAST} + gateway ${HOST_IP} +! + +# Have the guest start with an appropriate host name. +# Also record an entry for it in its own hosts file. +echo "${GUEST_HOSTNAME}" > "${TMP_MNT}/etc/hostname" +echo "${GUEST_IP} ${GUEST_HOSTNAME}" >> "${TMP_MNT}/etc/hosts" + +# The host will serve as the name server also +cat > "${TMP_MNT}/etc/resolv.conf" <<! +nameserver ${HOST_IP} +! + +# OK, done tweaking the boot image. +sync +umount "${DISK_IMAGE_A}" +rmdir "${TMP_MNT}" + +# Set up a config file for "ifup" and "ifdown" (on the host) to use. +# All the backslashes below are needed because we're sitting inside +# a double here-document... +cat > "${TAP_IFUPDOWN_CONFIG}" <<! +iface ${TAP} inet manual + up brctl addif virbr0 "\\\${IFACE}" + up ip link set dev "\\\${IFACE}" up + pre-down brctl delif virbr0 "\\\${IFACE}" + pre-down ip link del dev "\\\${IFACE}" + tunctl_user $(whoami) +! + +# OK, bring up the tap device using our config file +ifup -i "${TAP_IFUPDOWN_CONFIG}" "${TAP}" + +EnD_Of_sUdO + +# Finally ready to launch the UML instance. +./linux \ + umid="${GUEST_HOSTNAME}" \ + ubda="${DISK_IMAGE_A}" \ + eth0="tuntap,${TAP}" \ + mem=1024M + +# When we're done, clean up. Bring down the tap interface and +# delete the config file. +# +# Note that if the above "./linux" crashes, you'll need to run the +# following commands manually in order to clean up state. +sudo ifdown -i "${TAP_IFUPDOWN_CONFIG}" "${TAP}" +sudo rm -f "${TAP_IFUPDOWN_CONFIG}" + +exit 0 |