Help… run nsenter

Per Enqueue Zero, Nsenter is a utility enters the namespaces of one or more other processes and then executes the specified program. In other words, we jump to the inner side of the namespace.

Search for the namespace, by searching for S+, and then using the PID to target the namespace, and run the local tools in the namespace. This is very helpful where the docker container does not contain the necessary tools by default.

[root@localhost ~]# ps aux | grep 'S+'
gdm         1203  0.0  0.0   6084  1064 tty1     S+    2021   0:00 dbus-run-session -- gnome-session --autostart /usr/share/gdm/greeter/autostart
root       24439  0.0  0.0   4420   632 pts/0    S+    2021   0:00 tail -f /database/config/db2inst1/sqllib/db2dump/DIAG0000/db2diag.log
root      922523  0.0  0.0 221568   776 pts/0    S+   14:07   0:00 grep --color=auto S+
[root@localhost ~]# nsenter --target 24439 --mount --uts  --net --pid ps aux
USER         PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root           1  0.0  0.0  12100  2416 pts/0    Ss+   2021   0:01 /bin/bash /var/db2_setup/lib/setup_db2_instance.sh
root       14738  0.0  0.0 111996  5688 ?        Ss    2021  33:46 /usr/bin/python /usr/bin/supervisord -c /etc/supervisord.conf
root       14741  0.0  0.0   4420   632 pts/0    S+    2021   0:00 tail -f /database/config/db2inst1/sqllib/db2dump/DIAG0000/db2diag.log
root       14742  0.0  0.0  95724 12332 ?        S     2021   5:59 /opt/ibm/db2/V11.5/bin/db2fmcd
root       14743  0.0  0.0 112952  5696 ?        S     2021   0:00 /usr/sbin/sshd -D
root       65263  0.0  0.0 1313568 8708 ?        Sl    2021   0:06 db2wdog 0 [db2inst1]
db2inst1   65265  0.1  0.1 3716884 30216 ?       Sl    2021  88:11 db2sysc 0
root       65271  0.0  0.0 1316348 3548 ?        S     2021   0:00 db2ckpwd 0
root       65272  0.0  0.0 1316348 3548 ?        S     2021   0:00 db2ckpwd 0
root       65273  0.0  0.0 1316348 3544 ?        S     2021   0:00 db2ckpwd 0
db2inst1   65275  0.0  0.0 723620  7448 ?        S     2021   0:00 db2vend (PD Vendor Process - 1) 0
db2inst1   65283  0.0  0.1 961132 23452 ?        Sl    2021  16:42 db2acd 0 ,0,0,0,1,0,0,00000000,0,0,0000000000000000,0000000000000000,00000000,00000
db2fenc1   66416  0.0  0.1 650952 20416 ?        Sl    2021   0:01 db2fmp ( ,1,0,0,0,0,0,00000000,0,0,0000000000000000,0000000000000000,00000000,00000
db2fenc1   70651  0.0  0.1 424932 19852 ?        Sl    2021   0:00 db2fmp ( ,0,0,0,0,0,0,00000000,0,0,0000000000000000,0000000000000000,00000000,00000
db2fenc1 2274960  0.0  0.1 424932 19872 ?        Sl    2021   0:00 db2fmp ( ,0,0,0,0,0,0,00000000,0,0,0000000000000000,0000000000000000,00000000,00000
root     4113980  0.0  0.0  11704  2660 ?        S    19:05   0:00 bash -c /var/db2_setup/lib/backup_cfg.sh >> /tmp/backup_cfg.out 2>&1
root     4113981  0.0  0.0  11704  2816 ?        S    19:05   0:00 /bin/bash /var/db2_setup/lib/backup_cfg.sh
root     4114110  0.0  0.0   4380   736 ?        S    19:05   0:00 sleep 2m
root     4114269  0.1  0.0  12100  3072 ?        S    19:07   0:00 /bin/bash /var/db2_setup/lib/fix_etc_host.sh
root     4114285  0.0  0.0   4380   716 ?        S    19:07   0:00 sleep 10
root     4114290  0.0  0.0  53348  3856 pts/0    R+   19:07   0:00 ps aux
[root@localhost ~]#

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