mirrors/flatcar-scripts
1
0
Fork 0
mirror of https://github.com/flatcar/scripts.git synced 2025-08-08 13:36:58 +02:00
Code Issues Packages Projects Releases Wiki Activity

enter_chroot: introduce a sync process that synchronizes given files between chroot and host

Browse Source 
Currently used for resolv.conf and hosts, because these files can
change during the lifetime of a chroot, for example on computers
with more dynamic network (laptops).

While this creates a persistent process in the background for the
sole purpose of syncing files, the performance impact is negligible.

BUG=12316
TEST=below
1) enter_chroot once+quit, many times + quit, verify correct exit
behaviour
2) enter_chroot, modify host resolv.conf, see chroot being updated

Change-Id: I26573570c027acc2c214a00838a6f982a7585b13

R=robotboy@chromium.org,dparker@chromium.org,sosa@chromium.org

Review URL: http://codereview.chromium.org/6720005
This commit is contained in:
Zdenek Behan 2011-04-07 00:37:20 +02:00
parent b3cf233d4c
commit e28239d294
1 changed files with 38 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
enter_chroot.sh
View File

@ -129,6 +129,7 @@ SAVED_AUTOMOUNT_PREF_FILE="/tmp/.automount_pref"
sudo chmod 0777 "$FLAGS_chroot/var/lock"
LOCKFILE="$FLAGS_chroot/var/lock/enter_chroot"
SYNCERPIDFILE="${FLAGS_chroot}/var/tmp/enter_chroot_sync.pid"
function ensure_mounted {
@ -153,12 +154,46 @@ function ensure_mounted {
fi
}
function env_sync_proc {
# This function runs and performs periodic updates to the chroot env, if
# necessary.
local poll_interval=10
local sync_files="etc/resolv.conf etc/hosts"
# Make sure the synced files are writable by normal user, so that we
# don't have to sudo inside the loop.
for file in ${sync_files}; do
sudo chown ${USER} ${FLAGS_chroot}/${file} 1>&2
done
while true; do
# Sync files
for file in ${sync_files}; do
if ! cmp /${file} ${FLAGS_chroot}/${file} &> /dev/null; then
cp -f /${file} ${FLAGS_chroot}/${file}
fi
done
sleep ${poll_interval}
done
}
function setup_env {
# Validate sudo timestamp before entering the critical section so that we
# don't stall for a password while we have the lockfile.
# Don't use sudo -v since that has issues on machines w/ no password.
sudo echo "" > /dev/null
# Syncer proc, but only the first time
if ! [ -f "${SYNCERPIDFILE}" ] || \
! [ -d /proc/$(cat "${SYNCERPIDFILE}") ]; then
debug "Starting sync process"
env_sync_proc &
echo $! > "${SYNCERPIDFILE}"
disown $!
fi
(
flock 200
echo $$ >> "$LOCKFILE"
@ -283,6 +318,9 @@ function teardown_env {
debug "At least one other pid is running in the chroot, so not"
debug "tearing down env."
else
debug "Stopping syncer process"
kill $(cat "${SYNCERPIDFILE}")
MOUNTED_PATH=$(readlink -f "$FLAGS_chroot")
debug "Unmounting chroot environment."
# sort the list of mounts in reverse order, to ensure umount of