aboutsummaryrefslogtreecommitdiff
path: root/buildos
blob: 512bf27264e1ee786f15e74dbfb0621751b5babc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
#!/bin/bash

# Build OS monitor. It starts as a systemd service and performs the following
# steps:
#
# 1. Bootstrap the build2 toolchain.
# 2. Build and start bbot.
# 3. Build and start bslave.
# 4. Monitor for OS and toolchain changes and reboot if detected.
#

# @@ What will systemd do if we fail? Perhaps configure it to restart
#    us? Or not since we may hose the logs.
#
owd="$(pwd)"
trap "{ cd '$owd'; exit 1; }" ERR
set -o errtrace   # Trap in functions.
shopt -s nullglob # Expand patterns than don't match to empty.

# Note: diagnostics goes to stdout.
#
function info () { echo "$*" 1>&2; }
function error ()
{
  if [ "$#" -gt 0 ]; then
    info "$*";
  fi

  exit 1
}

info "starting build os monitor..."

# Parse the kernel command line. This is complicated by the fact that the
# values can be quoted, for example:
#
# foo='foo fox'
# bar="bar 'box'"
#
# First we separete quoted variables and arguments with newlines (giving
# priority to assignments). Then we replace whitespaces with newline on
# lines that don't contain quites. Finally, clean up by removing blank
# lines.
#
# Note: the same code as in init.
#
readarray -t cmdline < <(cat /proc/cmdline | \
  sed -r -e "s/([^ ]+=)?('[^']*'|\"[^\"]*\")/\n\1\2\n/g" | \
  sed -r -e "/['\"]/!s/ /\n/g" |
  sed -r -e '/^\s*$/d')

# Enter all buildos variables as bash variables.
#

# Map of toolchain names (as specified in buildos.<var>.<name>) to the
# corresponding bash variable prefix.
#
declare -A toolchains
toolchains["default"]=""

for v in "${cmdline[@]}"; do
  var="$(sed -n -re 's/^buildos\.([^=]+)=.*$/\1/p' <<<"$v")" # Extract name.

  if [ -n "$var" ]; then
    val="$(sed -re 's/^[^=]+=(.*)$/\1/' <<<"$v")"            # Extract value.
    val="$(sed -re "s/^('(.*)'|\"(.*)\")$/\2\3/" <<<"$val")" # Strip quoted.

    # If the variable contains a dot, then it is a toolchain variable.
    #
    if [[ "$var" == *.* ]]; then
      tn="$(sed -re 's/^[^.]+\.(.+)$/\1/' <<<"$var")"
      var="${tn}_$(sed -re 's/^([^.]+)\..+$/\1/' <<<"$var")"
      toolchains["$tn"]="${tn}_"
    fi

    declare "$var=$val"
  fi
done

hname="$(hostname)"

# Get the build id.
#
buildid="$(sed -n -re 's/^BUILD_ID="(.+)"$/\1/p' /etc/os-release)"

function email () # <subject> < <body>
{
  (echo -e "Subject: [$hname] $1\n"; cat -) | sendmail -i "$admin_email"
}

function restart ()
{
  sendmail -q # Flush mail queue.
  sleep 10    # Give any remaining mail chance to go through.
  sudo systemctl reboot
}

# Process toolchains.
#

# Return the value of one of the toolchain_* variables for this toolchain.
#
function tc_value () # <toolchain-prefix> <variable>
{
  local n="${1}${2}"
  echo "${!n}"
}

toolchain_names=()
for tn in "${!toolchains[@]}"; do
  tp="${toolchains["$tn"]}"
  tu="$(tc_value "$tp" toolchain_url)"

  if [ -z "$tu" ]; then
    continue
  fi

  toolchain_names+=("$tn")

  # The toolchain "sums" file (a list of SHA sums and relative file names, as
  # produced by shaNNNsum). The first entry should always be build2-toolchain
  # tar archive itself (which we use to figure out the version). Blank lines
  # and lines that start with '#' are ignored.
  #
  tf="$(sed -n -re 's%^.+/([^/]+)$%\1%p' <<<"$tu")"

  declare "${tp}toolchain_file=$tf"
  declare "${tp}toolchain_csum=$(sed -n -re 's%^.+\.([^.]+)$%\1%p' <<<"$tf")"
  declare "${tp}toolchain_root=/build/tftp/toolchain/$tn"
  declare "${tp}toolchain_ver="

  # If buildos.toolchain_trust was not specified, set it to "no" so that
  # we don't prompt if the repository happens to be signed.
  #
  if [ -z "$(tc_value "$tp" toolchain_trust)" ]; then
    declare "${tp}toolchain_trust=no"
  fi
done

# Divide CPUs and RAM (in kB) among the toolchains.
#
# Reserve 4G of RAM for ourselves (rootfs, tmpfs).
#
ram_total="$(sed -n -re 's/^MemTotal: *([0-9]+) *kB$/\1/p' </proc/meminfo)"
cpu_total="$(lscpu | sed -n -re 's/^CPU\(s\): *([0-9]+)$/\1/p')"

ram_slice=$(("$ram_total" - 4 * 1024 * 1024))
cpu_slice="$cpu_total"

if [ "${#toolchain_names[@]}" -gt 1 ]; then
  ram_slice=$(("$ram_slice" / "${#toolchain_names[@]}"))
  cpu_slice=$(("$cpu_slice" / "${#toolchain_names[@]}"))

  if [ "$cpu_slice" -eq 0 ]; then
    cpu_slice=1
  fi
fi

# Print monitor configuration as email body.
#
function print ()
{
  echo "cpu_total: $cpu_total"
  echo "cpu_slice: $cpu_slice"

  echo "ram_total: $ram_total kB"
  echo "ram_slice: $ram_slice kB"
  echo

  echo "buildid:       $buildid"
  echo "buildid_url:   $buildid_url"
  echo

  for tn in "${toolchain_names[@]}"; do
    tp="${toolchains["$tn"]}"
    tu="$(tc_value "$tp" toolchain_url)"
    tt="$(tc_value "$tp" toolchain_trust)"

    echo "$tn.toolchain_url:   $tu"
    echo "$tn.toolchain_trust: $tt"
    echo
  done
}

print | email "starting build os monitor"

if [ -z "$buildid_url" ]; then
  info "no buildos.buildid_url specified, not monitoring for new os builds"
fi

if [ "${#toolchain_names[@]}" -eq 0 ]; then
  info "no buildos.toolchain_url specified, not bootstrapping"
fi

# Cleanup /build/machines/ of any stray snapshots or deleted machines.
#
diag=()
fail=
for v in /build/machines/*; do
  if [ ! -d "$v" ]; then
    diag+=("$v: error: invalid volume")
    fail="true"
    continue
  fi

  cd "$v"

  for m in *; do
    if [ ! -d "$m" ]; then
      diag+=("$v/$m: error: invalid machine")
      fail="true"
      continue
    fi

    cd "$m"

    # Collect current machine symlink's bootstrap protocol numbers. If there
    # are no current machine symlinks, then we delete the whole thing.
    #
    ps=()
    for s in "$m"-*; do
      if [[ "$s" =~ ^"$m"-[0-9]+$ ]]; then

	if [ ! -L "$s" ]; then
	  diag+=("$v/$m/$s: error: not a symlink")
	  fail="true"
	fi

	# Treat it as if it were a symlink even if its not. Failed that we
	# may try to delete the whole thing.
	#
	ps+=("$(sed -n -re 's/^.+-([0-9]+)$/\1/p' <<<"$s")")
      fi
    done

    # Examine each machine subvolume.
    #
    for s in "$m"-*; do

      # <name>-<P> (current machine symlink)
      #
      if [[ "$s" =~ ^"$m"-[0-9]+$ ]]; then
	continue
      fi

      if [ ! -d "$s" ]; then
	diag+=("$v/$m/$s: error: invalid machine subvolume")
	fail="true"
	continue
      fi

      # Unless we are deleting the whole thing, keep initial and bootstrapped
      # (for known toolchains) subvolumes.
      #
      if [ "${#ps[@]}" -gt 0 ]; then

	# <name>-<P>.<R> (initial image)
	#
	f=
	for p in "${ps[@]}"; do
	  if [[ "$s" =~ ^"$m"-"$p"\.[0-9]+$ ]]; then
	    f="true"
	    break
	  fi
	done

	if [ -n "$f" ]; then
	  continue
	fi

	# <name>-<toolchain> (bootstrapped image)
	#
	f=
	for tn in "${toolchain_names[@]}"; do
	  if [[ "$s" =~ ^"$m"-"$tn"$ ]]; then
	    f="true"
	    break
	  fi
	done

	if [ -n "$f" ]; then
	  continue
	fi
      fi

      # This is either a stray working submodule or a bootsrapped subvolume
      # for a toolchain that was deleted (or we are deleting everything).
      #
      if ! btrfs property set -ts "$s" ro false; then
	diag+=("$v/$m/$s: error: unable to change subvolume property")
	fail="true"
	continue
      fi

      if ! btrfs subvolume delete "$s"; then
	diag+=("$v/$m/$s: error: unable to delete subvolume")
	fail="true"
	continue
      fi

      diag+=("$v/$m/$s: info: deleted subvolume")
    done

    cd "$v"

    # Delete the machine directory (which we expect to be now empty).
    #
    if [ "${#ps[@]}" -eq 0 ]; then
      if ! rmdir "$m"; then
	diag+=("$v/$m: error: unable to delete machine directory")
	fail="true"
	continue
      fi

      diag+=("$v/$m: info: deleted machine directory")
    fi
  done
  cd "$owd"
done

function print_diag ()
{
  local p
  for p in "${diag[@]}"; do
    echo "  $p"
  done
}

if [ "${#diag[@]}" -gt 0 ]; then
  if [ -z "$fail" ]; then
    s="cleaned up entries in /build/machines/"
  else
    s="invalid entries in /build/machines/, halting"
  fi

  print_diag | email "$s"
  info "$s" && print_diag 2>&1

  if [ -n "$fail" ]; then
    info "correct and restart the monitor (systemctl restart buildos)"
    exit 1
  fi
fi

# Toolchain-related funtions.
#

# Calculate the file checksum using the shaNNNsum utility.
#
function tc_checksum () # <toolchain-prefix> <file>
{
  "$(tc_value "$1" toolchain_csum)sum" -b "$2" | \
    sed -n -re 's/^([^ ]+) .+$/\1/p'
}

# Fetch a file from the sums file into $toolchain_root, verify its checksum,
# and make a predictable name (without version) symlink.
#
function tc_fetch () # <toolchain-prefix> <line>
{
  local s p f u l tp tu tr tv

  tp="$1"
  tu="$(tc_value "$tp" toolchain_url)"
  tr="$(tc_value "$tp" toolchain_root)"

  s="$(sed -n -re 's/^([^ ]+) .+$/\1/p' <<<"$2")"       # Checksum.
  p="$(sed -n -re 's/^[^ ]+ \*([^ ]+)$/\1/p' <<<"$2")"  # File path (relative).
  f="$(sed -n -re 's%^(.+/)?([^/]+)$%\2%p' <<<"$p")"    # File name.
  u="$(sed -n -re 's%^(.+)/[^/]+$%\1%p' <<<"$tu")/$p"   # File URL.

  if [ -z "$s" -o -z "$p" -o -z "$f" -o -z "$u" ]; then
    info "invalid sum line '$2'"
    return 1
  fi

  # Extract the version.
  #
  tv="$(tc_value "$tp" toolchain_ver)"

  if [ -z "$tv" ]; then
    tv="$(sed -n -re 's/build2-toolchain-(.+)\.tar.*/\1/p' <<<"$f")"

    if [ -z "$tv" ]; then
      info "unable to extract toolchain version from '$f'"
      return 1
    fi

    declare -g "${tp}toolchain_ver=$tv"

    info "toolchain version $tv"
    echo "$tv" >"$tr/version"
  fi

  # Derive a predictable name link.
  #
  l="$(sed -n -re "s/^(.+)-$tv(.*)$/\1\2/p" <<<"$f")"

  if [ -z "$l" ]; then
    info "unable to derive predicatable name from '$f' and '$tv'"
    return 1
  fi

  # Fetch the file.
  #
  info "fetching $u [$l]"

  if ! curl -f -L -s -S -o "$tr/$f" "$u"; then
    info "unable to fetch $u"
    return 1
  fi

  # Verify the checksum.
  #
  info "verifying checksum for $f"

  local cs
  cs="$(tc_checksum "$tp" "$tr/$f")"

  if [ "$cs" != "$s" ]; then
    info "checksum mismatch for $u"
    info "  expected:   $s"
    info "  calculated: $cs"
    return 1
  fi

  # Make the link.
  #
  ln -s "$f" "$tr/$l"
}

# Bootstrap the toolchain.
#
function tc_bootstrap () # <toolchain-name>
{
  local tn="$1"
  local tp="${toolchains["$tn"]}"
  local tr="$(tc_value "$tp" toolchain_root)"
  local tf="$(tc_value "$tp" toolchain_file)"

  # Fetch files according to the sums file. Skip empty lines and those that
  # start with '#'.
  #
  local l ls=()

  readarray -t ls < <(sed -e '/^\s*#/d;/^\s*$/d' "$tr/$tf")

  for l in "${ls[@]}"; do
    if ! tc_fetch "$tp" "$l"; then
      return 1 # Diagnostics has already been issued.
    fi
  done

  local tv="$(tc_value "$tp" toolchain_ver)"   # Should be set by tc_fetch().
  local tt="$(tc_value "$tp" toolchain_trust)"

  # Bootstrap in /tmp/toolchain/$tn/, install to /build/toolchain/$tn/.
  #
  local wd="/tmp/toolchain/$tn"
  local id="/build/toolchain/$tn"

  mkdir -p "$wd"
  mkdir -p "$id"

  local r=1

  cd "$wd"
  while true; do # The "breakout loop".

    # Extract the toolchain.
    #
    if ! tar -xf "$tr/build2-toolchain.tar.xz"; then
      info "unable to extract $tr/build2-toolchain.tar.xz"
      break
    fi

    cd "build2-toolchain-$tv"

    # Bootstrap, stage, and install using the provided build.sh script.
    #
    if ! ./build.sh --install-dir "$id" --trust "$tt" g++; then
      info "failed to build $(pwd)"
      break
    fi

    cd "$wd"
    rm -r "build2-toolchain-$tv"
    mv -T build2-toolchain-* build2-toolchain # Strip version.

    r=0
    break
  done
  cd "$owd"

  return "$r"
}

# Check if we need to build/start or rebuild/restart the bbot agent. Return
# 0 if nothing to do, 1 for upgrades, 2 for first build, and 3 for failure.
#
function bb_check () # <toolchain-name>
{
  local tn="$1"

  export PATH="/build/toolchain/$tn/bin:$PATH" # Running in subshell.

  cd "/tmp/toolchain/$tn/build2-toolchain"

  local r=3

  local l_stat b_stat
  while true; do # The "breakout loop".

    l_stat="$(bpkg status libbbot)"
    b_stat="$(bpkg status bbot)"

    if ! bpkg fetch -q; then
      info "failed to fetch package information"
      break
    fi

    # See if this is the first time or if we need to upgrade.
    #
    if [ "$(cut -d ' ' -f 1 <<<"$b_stat")" = "configured" ]; then

      # We assume that if anything has changed in the status line, then we
      # have a new version.
      #
      if [ "$b_stat" = "$(bpkg status bbot)" -a \
           "$l_stat" = "$(bpkg status libbbot)" ]; then
	r=0
	break
      fi

      r=1
      break
    fi

    r=2
    break
  done
  cd "$owd"

  return "$r"
}

# Build and start bbot agent using the bpkg configuration created by
# tc_bootstrap().
#
function bb_start () # <toolchain-name>
{
  local tn="$1"

  local id="/build/bbot/$tn"
  mkdir -p "$id"

  # Install/uninstall vars.
  #
  local vars=(config.install.root="$id" config.bin.rpath="$id/lib")

  export PATH="/build/toolchain/$tn/bin:$PATH" # Running in subshell.

  cd "/tmp/toolchain/$tn/build2-toolchain"

  local r=1

  local b_word
  while true; do # The "breakout loop".

    b_word="$(bpkg status bbot | cut -d ' ' -f 1)"

    # If upgrading, stop the service and uninstall.
    #
    if [ "$b_word" = "configured" ]; then

      if ! sudo systemctl stop "bbot-agent@$tn"; then
	info "failed to stop bbot-agent@$tn service, assuming not running"
      fi

      if ! bpkg uninstall "${vars[@]}" bbot; then
	info "failed to uninstall bbot agent"
	break
      fi
    fi

    # Build and install the bbot agent.
    #
    if ! bpkg build --build-option --jobs --build-option "$cpu_slice" \
	   --yes libbbot bbot; then
      info "failed to build bbot agent"
      break
    fi

    if ! bpkg install "${vars[@]}" bbot; then
      info "failed to install bbot agent"
      break
    fi

    # Post-process and install systemd .service file. Note that we cannot use
    # the systemd pattern machinery since each version of bbot can have its
    # own version of the .service file.
    #
    sed -i -r \
	-e "s/%[iI]/$tn/g" \
	-e "s/^(Environment=CPU)=.*/\1=$cpu_slice/" \
	-e "s/^(Environment=RAM)=.*/\1=$ram_slice/" \
	"$id/lib/systemd/system/bbot-agent@.service"

    sudo ln -sf "$id/lib/systemd/system/bbot-agent@.service" \
      "/usr/lib/systemd/system/bbot-agent@$tn.service"

    # Start the service. With Type=simple start returns as soon as the process
    # has forked. To see if the service actually started we wait a bit and
    # check with status.
    #
    if ! sudo systemctl start "bbot-agent@$tn"; then
      info "failed to start bbot-agent@$tn service"
      break
    fi

    if ! sudo systemctl status "bbot-agent@$tn"; then
      info "failed to start bbot-agent@$tn service"
      break
    fi

    r=0
    break
  done
  cd "$owd"

  return "$r"
}

# Array of bootstrapped toolchains.
#
# The idea is to collect them until we bootstrap all of them and only then
# start their bbot agents.
#
toolchain_boots=()

# Monitoring loop.
#
count=0
while true; do

  count=$(($count + 1))

  # Check for toolchain changes. If this is the first run, bootstrap them.
  #
  for tn in "${toolchain_names[@]}"; do
    tp="${toolchains["$tn"]}"
    tu="$(tc_value "$tp" toolchain_url)"

    tr="$(tc_value "$tp" toolchain_root)"
    tf="$(tc_value "$tp" toolchain_file)"
    p="$tr/$tf"

    mkdir -p "$tr"

    # Fetch the toolchain sums either to $p if this is the first time or to
    # $p.new if we are checking for changes.
    #
    if [ -e "$p" ]; then
      f="$p.new"
    else
      f="$p"
    fi

    if curl -f -L -s -S -o "$f" "$tu"; then

      # Take care of change detection.
      #
      if [ "$f" != "$p" ]; then

	ts="$(tc_value "$tp" toolchain_file_csum)"
	cs="$(tc_checksum "$tp" "$f")"

	if [ "$ts" != "$cs" ]; then
	  email "rebooting because of new $tn toolchain" <<EOF
old_checksum: $ts
new_checksum: $cs
EOF
	  info "new $tn toolchain ($cs), rebooting..."
	  restart
	fi
      else
	# This is the first run, bootstrap the toolchain.
	#
	declare "${tp}toolchain_file_csum=$(tc_checksum "$tp" "$f")"

	# If we fail, we simply wait for a new toolchain to be uploaded (or
	# some manual intervention).
	#
	# Note that because of the pipe tc_bootstrap() will run in subshell
	# and any variables it sets (like toolchain_ver) won't be visible to
	# us.
	#
	info "bootstrapping $tn toolchain..."

	tc_bootstrap "$tn" 2>&1 | tee "$tr/bootstrap-$count.log" 1>&2

	if [ "${PIPESTATUS[0]}" -eq 0 ]; then
	  v="$(cat $tr/version)"
	  declare "${tp}toolchain_ver=$v"

	  s="bootstrapped $tn toolchain $v"
	  toolchain_boots+=("$tn")
	else
	  s="failed to bootstrap $tn toolchain, waiting for new version"
	  toolchain_boots+=("") # Skip.
	fi

	info "$s"
	email "$s" <<EOF
$tn.bootstrap_log: tftp://$hname/toolchain/$tn/bootstrap-$count.log
EOF
      fi
    else
      info "unable to fetch $tu, will try again"
      rm -f "$f"
    fi
  done

  # If we have boostrapped all the toolchains, (re)build and (re)start their
  # bbot agents.
  #
  if [ "${#toolchain_names[@]}" -eq "${#toolchain_boots[@]}" ]; then

    for tn in "${toolchain_boots[@]}"; do

      # Skip those that failed to bootstrap.
      #
      if [ -z "$tn" ]; then
	continue
      fi

      s=
      bb_check "$tn" 2>&1 | tee "$tr/bbot-$count.log" 1>&2

      case "${PIPESTATUS[0]}" in
	0)
	  rm -f "$tr/bbot-$count.log"
	  continue # Nothing to do.
	  ;;
	1)
	  s="re"
	  ;&
	2)
	  info "${s}starting bbot-agent@$tn..."

	  # Append to the same log.
	  #
	  bb_start "$tn" 2>&1 | tee -a "$tr/bbot-$count.log" 1>&2

	  if [ "${PIPESTATUS[0]}" -eq 0 ]; then
	    s="${s}started bbot-agent@$tn"
	  else
	    s="failed to ${s}start bbot-agent@$tn, waiting for new version"
	  fi
	  ;;
	*)
	  s="failed to fetch package information for $tn, will try again"
	  ;;
      esac

      info "$s"
      email "$s" <<EOF
$tn.start_log: tftp://$hname/toolchain/$tn/bbot-$count.log
EOF
    done
  fi

  # Check for OS changes.
  #
  if [ -n "$buildid_url" ]; then
    # Fetch the current id. While normally it will be a TFTP URL, it could also
    # be HTTP(S) so we configure sensible behavior for that.
    #
    if id="$(curl -f -L -s -S "$buildid_url")"; then
      if [ "$id" != "$buildid" ]; then
	email "rebooting because of new os build" <<EOF
old_buildid: $buildid
new_buildid: $id
EOF
	info "new os build ($id), rebooting..."
	restart
      fi
    else
      info "unable to fetch $buildid_url, will try again"
    fi
  fi

  info "monitoring..."
  sleep 20
done