Ubiquiti ERL script wanted to compare md5 values

JaredBusch

I recently had one of the older model ERL die at a client site. I had a spare handy so I loaded a backup of their config on it and overnighted it.

Their old one came back and the file system was corrupted. I suspect maybe the USB drive is dieing. There is a known low opinion of the quality of the USB in the first models (the ones in the plastic case with beveled corners).

I have already flashed it and it is working fine, but I just came across a post on the UBNT community from one user stating that ever system that he has had failed due to a USB drive was showing MD5 differences in the system.

He suggested running the following:

md5sum /root.dev/squashfs.img /root.dev/squashfs.o
#results in:
dd15068cb6e3d7261a5a0877dc05aa5d  /root.dev/squashfs.img
5d97f65401e0ae61969e29f66270b438  /root.dev/squashfs.o

comparing that to the state md5 value shows they match for me right now.

vi /root.dev/squashfs.img.md5
dd15068cb6e3d7261a5a0877dc05aa5d

and

vi /root.dev/squashfs.o.md5
5d97f65401e0ae61969e29f66270b438

So now I want to setup a script to run this command and check the files and spit out a pass/fail result.z

Linux administration is not my strong point. Linux shell scripting, even less so.

JaredBusch

I tried simply

admin@aci:~$ md5sum -c /root.dev/squashfs.img.md5
md5sum: WARNING: 1 of 1 computed checksums did NOT match
admin@aci:~$

scottalanmiller

So you have the command that does the comparison. Looks like that's the right starting point. What more do you want it to do? Want it to actually state pass or fail?

JaredBusch

Creating my own md5 file I found the problem is that the current md5 does not contain the file path for the -c to test on..

md5sum /root.dev/squashfs.img /root.dev/squashfs.o > /config/md5test.md5
# results in
vi /config/md5test.md5
dd15068cb6e3d7261a5a0877dc05aa5d  /root.dev/squashfs.img
5d97f65401e0ae61969e29f66270b438  /root.dev/squashfs.o
#and now tests as
md5sum -c /config/md5test.md5
/root.dev/squashfs.img: OK
/root.dev/squashfs.o: OK

JaredBusch

So now, how to integrate this or something to email me when they don't match.

:sigh:
too many thing I need to do at once..

scottalanmiller

So on failure is denoted by ||

scottalanmiller

So you can do...

thing you want to test || thing to do when it fails

scottalanmiller

So in your case:

md5sum -c /config/md5test.md5 || mail -s "You have a failure in your md5" [email protected]

scottalanmiller

If you needed to do the opposite where instead of failure you want to do something only on success you would use && instead of ||

scottalanmiller

You may need to install mailx, which supplies the mail command. It is very easy to work with for sending emails from a Linux system.

JaredBusch

So you are implying that if the result is not ok for everything in the file that md5sum would execute the error condition if present?

I have not read the man file on md5sum at this point yet.

scottalanmiller

@JaredBusch said:

So you are implying that if the result is not ok for everything in the file that md5sum would execute the error condition if present?

Correct. But before you start emailing willy nilly, try this test example

md5sum -c /config/md5test.md5 || echo "Fail"

scottalanmiller

You can try with passing and failing md5sums and see if it actions the echo or not.

JaredBusch

Yup, that does it.

jbusch@jared:~$ md5sum -c /config/md5test.md5 || echo "Fail"
/root.dev/squashfs.img: OK
md5sum: can't open '/root.dev/squashfs.': No such file or directory
/root.dev/squashfs.: FAILED
md5sum: WARNING: 1 of 2 computed checksums did NOT match
Fail
jbusch@jared:~$

scottalanmiller

Add this to clean it up...

md5sum -c /config/md5test.md5 2>/dev/null || echo "Fail"

JaredBusch

looking at what i need to do to send an email. The documentation for ERL sucks as it is mostly community created and the package stuff changed with firmware 1.6.0

scottalanmiller

Also try it with good md5 sums to make sure it does nothing when they are successfully matched. Just to be sure.

scottalanmiller

@JaredBusch said:

looking at what i need to do to send an email. The documentation for ERL sucks as it is mostly community created and the package stuff changed with firmware 1.6.0

Oh shoot, forgot that it was ERL. Might not use the same mail command at all. That's a common syntax, but certainly not the only one.

JaredBusch

@scottalanmiller said:

Also try it with good md5 sums to make sure it does nothing when they are successfully matched. Just to be sure.

I did.

jbusch@jared:~$ md5sum -c /config/md5test.md5 echo && "Successful test of MD5" || echo "Failed test of MD5"
/root.dev/squashfs.img: OK
/root.dev/squashfs.o: OK
md5sum: echo: No such file or directory
Failed test of MD5
jbusch@jared:~$ md5sum -c /config/md5test.md5 && echo "Successful test of MD5" || echo "Failed test of MD5"
/root.dev/squashfs.img: OK
/root.dev/squashfs.o: OK
Successful test of MD5
jbusch@jared:~$

scottalanmiller

The first one "worked" because you put in three commands and the middle one had a typo so failed caused the third one to trigger. You didn't test what you think that you tested.