Hey. I just noted something odd. What I do is, construct (in a shell script) and execute a ssh command, which some (constructed) options set and executes an (also constructed and quite long) remote shell command. When I do this on a connection for which I have control channel muxing set up, the [mux] process gets very long cmdline. The following is, when the (initiating) ssh command is still running: $ ps ax | grep ssh 4712 ? Ss 0:00 /usr/bin/ssh-agent cinnamon-session-cinnamon 543871 pts/18 S+ 0:00 ssh -o ClearAllForwardings=yes -o ForwardAgent=no -o ForwardX11=no -o ForwardX11Trusted=no -o GatewayPorts=no -o PermitLocalCommand=no -o PermitRemoteOpen=none -o UpdateHostKeys=no -o BatchMode=yes foo.grid.lrz.de set -e unset -v IFS export PATH='/usr/bin:/bin' export LC_ALL='C' cd / sleep 400 p="/tmp/x509up_u$(id -u)" t="$(mktemp)" { ?cat >"${t}" && ?mv -f --no-target-directory "${t}" "${p}" } || { rm -f "${t}" && exit 10 || exit 20; } ? { ? ?m="$(stat --printf='%Y' "${p}")" && ? ?h="$(sha256sum "${p}")" && ? ?{ [ -n "${p##*\'*}" ] && [ -n "${m##*\'*}" ] && [ -n "${h##*\'*}" ]; } && ? ? ? ?printf 'if [ "$(stat --printf='\''%%Y '\'' '\''%s'\''; sha256sum '\''%s'\'')" = '\''%s %s'\'' ]; then\n\trm -f '\''%s'\'';\nfi\n' "${p}" "${p}" "${m}" "${h}" "${p}" | ? ?env -i PATH="${PATH}" LC_ALL="${LC_ALL}" ? ?at -M 'now + 3 minutes' 2>&1 ? } || { rm -f "${p}" && exit 11 || exit 21; } ? 543876 ? Ss 0:00 ssh: /home/calestyo/.ssh/mux/root@foo.grid.lrz.de:22 [mux] 543888 pts/19 S+ 0:00 grep --color=auto ssh It probably cannot be seen well in bugzilla, but after the [mux] process there are numerous empty lines (actually just the spaces after the command). Once the initiating ssh is Ctrl-C'ed: $ ps ax | grep ssh 4712 ? Ss 0:00 /usr/bin/ssh-agent cinnamon-session-cinnamon 543689 pts/20 S+ 0:00 vi bin/ssh_killall-mux 543876 ? Ss 0:00 ssh: /home/calestyo/.ssh/mux/root@foo.grid.lrz.de:22 [mux] 544406 pts/19 S+ 0:00 grep --color=auto ssh again, with loads of empty lines. hd /proc/543876/cmdline 00000000 73 73 68 3a 20 2f 68 6f 6d 65 2f 63 61 6c 65 73 |ssh: /home/cales| 00000010 74 79 6f 2f 2e 73 73 68 2f 6d 75 78 2f 72 6f 6f |tyo/.ssh/mux/roo| 00000020 74 40 6c 63 67 2d 6c 72 7a 2d 61 64 6d 69 6e 2e |t@*privacy* foo.| 00000030 67 72 69 64 2e 6c 72 7a 2e 64 65 3a 32 32 20 5b |grid.lrz.de:22 [| 00000040 6d 75 78 5d 00 00 00 00 00 00 00 00 00 00 00 00 |mux]............| 00000050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000500 00 00 00 00 00 20 00 |..... .| 00000507 That may be quite annoying for anyone who e.g. uses pgrep to kill mux processes and expects the name to end after the "]" ;-) And another odd thing (please tell whether this is expected or not, cause then I'd open a new ticket): You've noticed the sleep 400 in my remote command (which was just there fore debugging)? Even when I Ctrl-C the (mux-initiating) ssh right after the start, the [mux] process lingers around for those 400+ControlPersist seconds. Well not exactly those it actually differs a few seconds... (which I found also a bit add). Shouldn't ControlPersist "start to count" when the last connection is gone and shouldn't that happen with the Ctrl-C? Thanks, Chris.