Has it ever happened to you that you remotely rebooted a Linux server and wondered why after 10 minutes you still couldn’t Ping or SSH into it? Quite often, this is caused by a lengthy run of fsck on one of your ext3 file systems (on current multi-TB disks, they can take an hour or longer). They usually get triggered automatically around every six months or 30 mounts, and there’s no easy way of knowing when it will happen.
My solution to this is rather simple: tune2fs -l tells you when the next fsck is coming up, so why not run a script upon every boot and have it write that information into /etc/motd so that you can see it every time you SSH in? The script is below (as a bonus, drives being fscked in less than 5 mounts or a week are printed in red), so all you need to do is put it somewhere on your hard drive and add something like
# Add FSCK status to MOTD
[ -f /root/fsck_stats.sh ] && bash /root/fsck_stats.sh >> /var/run/motd
to the init script that generates your motd (on Debian Squeeze, that would be /etc/init.d/bootlogs).
#!/bin/bash
echo
for disk in /dev/sda1 /dev/mapper/vm--storage-vms /dev/sdb1
do
cur_mounts=$(tune2fs -l $disk | grep "Mount count:" | awk '{print $3}')
max_mounts=$(tune2fs -l $disk | grep "Maximum mount count:" | awk '{print $4}')
diff_mounts=$(echo $max_mounts-$cur_mounts | bc)
last_check=$(tune2fs -l $disk | grep "Last checked:" | awk '{print $3}')
next_check=$(tune2fs -l $disk | grep "Next check after:" | awk '{print $4" "$5" "$6" "$7" "$8}')
next_check_timestamp=$(date -d "$next_check" "+%s")
cur_timestamp=$(date "+%s")
diff_next=$(echo $next_check_timestamp-$cur_timestamp | bc)
color=""
[ $diff_mounts -lt 5 ] && color="\033[31m"
[ $diff_next -lt 604800 ] && color="\033[31m"
echo -e "$color Next FSCK on $(basename $disk): $next_check or in $diff_mounts mounts\033[0m"