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I'm working on a sysprep-style script which de-identifies a machine and gets it ready for templatizing. The last task that I'd like to perform (before shutdown) is clearing the bash history for the root user. I can execute 

HISTFILE=~/.bash_history
set -o history
>$HISTFILE
history -c

from within the script. The issue is the history stored in memory for the interactive root session that executes the script is written to $HISTFILE at the end of that session. I want the sysprep script to be the last thing executed (the last line in the script is shutdown now -h).

If necessary, I can clear the history manually from the interactive session before shutdown, but I'd like to make it part of my script. Any suggestions?

Not sure if it matters but this is for RHEL8.

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  • 1
    What if you just disable history? Commented Dec 6, 2019 at 20:18
  • The sysprep script is executing in its own non-interactive shell, so should be unable to modify your shell. My best immediate thought would be to have the script chmod u-w the HISTFILE, but that would leave the HISTFILE unwritable going forward. Commented Dec 6, 2019 at 20:22
  • Unfortunately neither of these options are viable for my circumstance because I need history enabled for machines spawned from the template. Commented Dec 7, 2019 at 22:35

2 Answers 2

Reset to default
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The closest I can come up with is:

sysprep.sh

#!/bin/sh
# other steps
cp /dev/null ~/.bash_history
shutdown -h now

Followed by:

# exec /path/to/sysprep.sh

... instead of a direct call to /path/to/sysprep.sh. Using exec replaces your current shell with the shell script, which allows the current shell to write its history and exit. The sysprep script is then free to remove (or clear) your history file.

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  • (I used /bin/sh as the sh-bang, but use whatever you're using currently). The main point is the cp /dev/null line. Commented Dec 6, 2019 at 20:47
  • Thanks, this could work but I was hoping to have an all-inclusive solution. I won't be the only person editing this template moving forward, and I wanted to hand the other admins in my group a single script they could just call. Commented Dec 7, 2019 at 22:38
  • Well, the only modification (beyond adding the cp command to the script) is how you call it. Commented Dec 7, 2019 at 22:49
  • Jeff, Sorry...I misunderstood your original message. I originally thought it was your intention to put cp /dev/null ~/.bash_history outside the sysprep script. I've verified that this works. Thanks for the help. Commented Dec 12, 2019 at 17:17
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The history of the current shell is appended to $HISTFILE when the shell exits. Doing unset $HIST_FILE makes this not happen, so the history of that shell instance is lost when the shell exits.

So, as long as:

  1. the script is source-ed or exec-ed from an interactive shell, or called directly without an interactive shell
  2. the script unsets $HISTFILE before exiting

It can erase the history file, or replace it with whatever history you want to see later.

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