Re: [Libguestfs] [p2v PATCH 1/4] ssh: shield virt-v2v from bash RC files

I don't have virt-v2v installed system-wide on my RHEL9 laptop, I rely on the various "./run" scripts to put everything that virt-p2v's "make check" requires on the PATH environment variable. However, "test-virt-p2v-nbdkit.sh" still breaks for me; it complains that "virt-v2v --version" cannot be executed by test_connection(), due to "virt-v2v" not being found. Prefixing the "virt-v2v --version" invocation in test_connection() with "echo \"$PATH\"; ", I've determined from "test-virt-p2v-nbdkit.sh.log" that the *non-appending* PATH=... variable assignment from my $HOME/.bashrc takes effect. It wipes out the PATH changes from the "./run" scripts, hiding virt-v2v. I've added the following snippet to my $HOME/.bashrc file, for debugging: > XXX=mess-$(date --rfc-3339=ns)--$$.log > /bin/pstree -a -A -l -n -p $$ >| "$HOME/tmp/$XXX" so that whichever shell read the RC file create a log file, named with a nanosecond-resolution timestamp and the shell's PID, and record the "path" in the process tree that lead to the shell. The snippet created the following two files: > mess-2023-01-18 09:33:49.896065330+01:00--36312.log > mess-2023-01-18 09:33:49.937365639+01:00--36312.log containing, respectively: > bash,36312 > `-pstree,36315 -a -A -l -n -p 36312 and > bash,36312 --noediting --noprofile > `-pstree,36320 -a -A -l -n -p 36312 Note that the PID of the shell is unchanged, but the pstree PID changes. This means that the same PID (same process) reads the bash RC file twice -- which can only be explained by the *image* of the process being replaced, from bash, to bash. So the problem happens in two places: - First, when we "exec" the interactive shell in "test-virt-p2v-ssh.sh", that is, our ssh "shim". Interactive *non-login* shells read the RC file, unless the "--norc" option is passed. - Second, when we "exec" bash from start_ssh(), on the remote machine. This invocation already passes the "--noprofile" option, but that has no effect. "--noprofile" prevents the shell from reading "$HOME/.bash_profile" when the shell is a *login* shell, regardless of whether it is interactive or not. Because the existent "--noprofile" option does not prevent the symptom, we can determine that the remote shell started by start_ssh() is a *non-login* shell, and that it's also interactive (otherwise it wouldn't read the RC file). Thus, we need to pass "--norc" here as well. (While I believe, based on the above, that "--noprofile" is superfluous, I'd like to avoid any potential regressions here, so I'm keeping "--noprofile" too.) Append "--norc" to both command lines. Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; --- ssh.c | 2 +- test-virt-p2v-ssh.sh | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/ssh.c b/ssh.c index aeb57584cf55..513a20318359 100644 --- a/ssh.c +++ b/ssh.c @@ -469,7 +469,7 @@ start_ssh (unsigned spawn_flags, struct config *config, * We don't know how command line editing is set up * (https://bugzilla.redhat.com/1314244#c9). */ - if (mexp_printf (h, "exec bash --noediting --noprofile\n") == -1) { + if (mexp_printf (h, "exec bash --noediting --noprofile --norc\n") == -1) { set_ssh_mexp_error ("mexp_printf"); mexp_close (h); return NULL; diff --git a/test-virt-p2v-ssh.sh b/test-virt-p2v-ssh.sh index 8a14b71fbd4b..f8b86b539ffe 100755 --- a/test-virt-p2v-ssh.sh +++ b/test-virt-p2v-ssh.sh @@ -57,4 +57,4 @@ while true ; do done # Now run the interactive shell. -exec bash +exec bash --norc