Linux Troubleshooting

Force unmount a broken NFS mount	`umount -fl /mnt/nfsmount` `umount --force --lazy /mnt/nfsmount`
hard reset when `reboot` doesn't work	`echo 1 > /proc/sys/kernel/sysrq` `echo b > /proc/sysrq-trigger`
force luksClose when “Device is still in use”	`dmsetup remove -f luksName`
while upgrading, this message appears: `/usr/bin/perl: error while loading shared libraries: libcrypt.so.1: cannot open shared object file: No such file or directory`	`apt download libcrypt1` `dpkg-deb -x libcrypt1_1%3a4.4.33-2_arm64.deb .` `cp -av lib/aarch64-linux-gnu/* /lib/aarch64-linux-gnu/` `apt –fix-broken install`
Keep journals for only n days	`vim /etc/systemd/journald.conf` MaxRetentionSec=7day `systemctl restart systemd-jornald`