Checking the status of an array

[cburwell]

In an effort to get my RAID array to mount at boot time, I am writing a shell script to do all the work for me.

What I would like to do is use a boolean expression inside an if/else statement to see if the array /dev/md0 is currently active.

To check the status of an array by hand, I issue the command "sudo cat /proc/mdstat", which returns:


Personalities : [raid1]
md0 : active raid1 sda1[0] sdb1[1]
488383936 blocks [2/2] [UU]

unused devices: <none>


The if test i have is as follows:

if [cat /proc/mdstat|grep "md0 : active"]

When I run the script it gives me a "no such file or directory error".

Does anyone have any idea how to get this work? I am new to shell scripting, so I am sure I am missing something simple. Here is my entire if statement structure:


if [cat /proc/mdstat|grep "md0 : active"]
then
echo "RAID array exsists!" &
#Check if array is mounted
else
echo "Re-adding array: /dev/md0" &
mdadm -A /dev/md0 /dev/sda1 /dev/sdb1
echo "Mounting /dev/md0 to /var/shared" &
mount /dev/md0 /var/shared
echo "Changing ownership of /var/shared" &
echo "Changing group of /var/shared" &
#chown & chgrp /var/shared
echo "Restarting samba with: /etc/init.d/samba" &
/etc/init.d/samba restart
fi

[drl]

Hi.

Looks the common mistake of using

[cat

instead of

[ cat

Note the space between "[" and "cat" -- the character "[" is actually a command and so needs whitespace.

Using the [CODE] blocks helps forum folks see troubles like this. If that is not the problem, please post again ... cheers, drl

[cburwell]

Thank you! It was a combination of that, and the fact that the use of single and double quotes still had me confused! Here is the code that works.

if [ "cat /proc/mdstat|grep md0 : active" ]
                then
                        echo "RAID array exsists!" &
                        #Check if array is mounted
        else
                echo "Re-adding array: /dev/md0" &
                #mdadm -A /dev/md0 /dev/sda1 /dev/sdb1
                echo "Mounting /dev/md0 to /var/shared" &
                #mount /dev/md0 /var/shared
                echo "Changing ownership of /var/shared" &
                echo "Changing group of /var/shared" &
                #chown & chgrp /var/shared
                echo "Restarting samba with: /etc/init.d/samba" &
                #/etc/init.d/samba restart
        fi

[drl]

Hi.

OK, you got past the syntax error, but there is still a problem with the if (a semantic error).

The if takes a command and looks at the exit status, but you have if command command.

My suggestion is to do a few small test cases. You may want to refer to the very good tutorial around this topic: http://www.tldp.org/LDP/abs/html/testconstructs.html ... cheers, drl