1. truss -xall -vall -rall -t'read' -p PID #

   To run a command and have it produce debug info, run it prefix with the truss syntax:

   truss -xall -vall -rall -t'read' your command #

   Another good option when debugging, is to run truss and look at the opens. Or more specifically the failures - as this often highlights missing libraries or permissions issues.

   truss -t'open' -p PID #
2. On Linux use strace, which takes basically the same options. You just use -e, like this:
   strace -e'open' ls
   open("/etc/ld.so.preload", O_RDONLY) = -1 ENOENT (No such file or directory)
   open("/etc/ld.so.cache", O_RDONLY) = 3
   open("/lib/tls/librt.so.1", O_RDONLY) = 3
   open("/lib/libtermcap.so.2", O_RDONLY) = 3
   open("/lib/libacl.so.1", O_RDONLY) = 3
   open("/lib/tls/libc.so.6", O_RDONLY) = 3
   open("/lib/tls/libpthread.so.0", O_RDONLY) = 3
   open("/lib/libattr.so.1", O_RDONLY) = 3
   open("/usr/lib/locale/locale-archive", O_RDONLY|O_LARGEFILE) = 3
   open(".", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = 3
   open("/etc/mtab", O_RDONLY) = 3
   open("/proc/meminfo", O_RDONLY) = 3

1. System process debug (solaris) all exec/reads
   truss -xall -vall -rall -t'read' -p PID
2. Network trace connection from hostname (solaris)
   snoop -x0 src hostname
3. Optical dump of a file, useful for seeing control chars, etc and lines with no newline.
   od -c filename
4. Generate 512 bytes of random data, cat -ve escapes control chars.
   dd bs=1 count=512 if=/dev/urandom | cat -ve
5. list directory contents, display in 3 columns.
   ls | paste - - -
6. Loop through all files and perform an action on it.
   for na in * ; do echo $na ; done
7. Check for values in vars.
   [[ $(echo $var | grep -ic "pattern") -eq 0 ]] &

   You could also go for "-eq 1" - does contain or -ne 0 for same, etc. Plus you could use || for "or" either in place of "&&" or after this block - same as if .. then "positive" else "negative" fi.

8. Detach a process without it dying.
   disown [%1]
   nohup command > /tmp/logfile.log 2>&1&

   If you start a process with nohop (ignore the hup signal), it will not exist (usually) when your shell is exited. This can now be simulated on solaris, by backgrounding a process (with ctrl Z and bg) then typing disown. jobs command will show all backgrounded jobs. Ideally start commands like this, to avoid the shell exit problem:

9. Perform arithmetic in shell.
   bc -l

   Binary Calculator in long format - for float, etc. Can also be automated like this, to convert between decimal and hex:

   i=0; while ((i<20)) ; do echo -n "$i: "; echo "base=10;obase=16;$i" | bc; ((i++)); done | paste - - - -
   0: 0 1: 1 2: 2 3: 3
   4: 4 5: 5 6: 6 7: 7
   8: 8 9: 9 10: A 11: B
   12: C 13: D 14: E 15: F
   16: 10 17: 11 18: 12 19: 13

Anyway, I'm quite happy just using this little secret. Having used it many times:

The basic syntax looks like this:

od -c filename
Heres a demo:

Also useful if wanted to look at a binary file, without breaking your terminal. Or looking through encryption.

Also an easy converting of ascii to hex:

1. openssl code to generate self-signed cert
2. encrypt with tripledes
3. openssl base64 [ -d ]

   # encrypted with base64.

4. Useful fortransfering control/binary content - like this:
   dd bs=1 count=512 if=/dev/urandom | openssl base64

   Also useful for reading mail

   openssl base64 -d /var/spool/mqueue/qfk3GAlBMn018552
5. Using openssl s_client to test ciphers supported, with automated script - then loop sites and email.
6. Using openssl s_client to extract expiry dates, with automated script - then loop sites and email.

Simple as that, it will send the filename as an attachment to a blank email, with your subject.

Here is a demo:

To do multiple attachments, simply cat files - then uuencode them into a temp file. Like this:

Repeat this for say file2 into attach2 and send2. Then to send them all do this:

Add to beginning:

Add to the end:

Demo

Example of generating an email upon cron failure

Another example

Then run /etc/init.d/iptables restart

You can test if this connection is now viable, by using my Perl port testing code under Perl Coding School

Other gotchas with samba and nfs, was fiddling with selinux and ensuring portmap was running, etc. Happy to explain further, feel free to post a comment with your questions.

Openssl tripleDES encrypt command:

Place contents to encrypt in the file reference by file_to_encrypt

Replace your_password with your secret

Openssl will output to stdout - so best to capture like this:

Openssl tripleDES decrypt command:

Put cipher text to decrypt in filename supplied to -in

Replace _your_password_ with the secret

Outputs to stdout
See the full demo attached here for a blow by blow:

[ How to encrypt with openssl and tripleDES ]

To create a certificate request:

[ See a run through screen shot here ]

Self-sign the request - only do this if you are not sending off to a CA such as Verisign.

[ See a run through screen shot here ]

If you get 'unable to write random state', try this: look for command ssh-rand-helper usually under ssh install directories (or if ~/.ssh/.prng_seed exists - you can just link to it or copy it to $HOME).

To strip the password out, for restarts: