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--- linux:general:troubleshooting [2018/08/28 17:23] – lunetikk
+++ linux:general:troubleshooting [2019/10/07 18:06] – lunetikk
@@ Line 1: / Line 1: @@
 ===== Troubleshooting =====
+==== Removing old kernels leads to broken symlinks ====
+=== Description ===
+apt-get autoremove leads to a broken symlink which requires a reload of grub
+<code>
+apt-get autoremove
+...
+The link /vmlinuz.old is a damaged link
+Removing symbolic link vmlinuz.old
+ you may need to re-run your boot loader[grub]
+The link /initrd.img.old is a damaged link
+Removing symbolic link initrd.img.old
+ you may need to re-run your boot loader[grub]
+</code>
+=== Reason ===
+Broken symlinks
+=== Fix ===
+Run "update-grub"
+<code>
+update-grub
+ Generating grub configuration file ...
+ Found linux image: /boot/vmlinuz-3.13.0-157-generic
+ Found initrd image: /boot/initrd.img-3.13.0-157-generic
+ Found linux image: /boot/vmlinuz-3.13.0-153-generic
+ Found initrd image: /boot/initrd.img-3.13.0-153-generic
+ Found memtest86+ image: /boot/memtest86+.elf
+ Found memtest86+ image: /boot/memtest86+.bin
+ done
+</code>
+\\
+\\
 ==== Linux starts in emergency mode - faulty logical volume (xfs) ====
@@ Line 91: / Line 130: @@
 mysqld would have been started with the following arguments:
---user=mysql --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/run/mysqld/mysqld.sock --port=3306 --basedir=/usr --datadir=/var/lib/mysql --tmpdir=/tmp --lc-messages-dir=/usr/share/mysql --skip-external-locking --bind-address=127.0.0.1 --key_buffer=16M --max_allowed_packet=16M --thread_stack=192K --thread_cache_size=8 --myisam-recover=BACKUP --query_cache_limit=1M --query_cache_size=16M --log_error=/var/log/mysql/error.log --expire_logs_days=10 --max_binlog_size=100M
+--user=mysql --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/run/mysqld/mysqld.sock --port=3306...
 </code>
-Compare the defaults for "socket", both should be the same. If you get a different socket for your client, try to connect to your database by using the same
+Compare the defaults for "socket", both should be the same. If you get a different socket for your client, try to connect to your database by using the same as specified for mysqld
 <code>mysql --socket=/var/run/mysqld/mysqld.sock -hlocalhost -uroot -p</code>
@@ Line 124: / Line 163: @@
 The connection should work now.
+\\
+\\
+==== Bug: soft lockup in messages ====
+=== Description ===
+You can find multiple "Bug: soft lockup" entries in /var/log/messages or journalctl
+<code>
+May 25 07:23:59 XXXXXXX kernel: [13445315.881356] BUG: soft lockup - CPU#16 stuck for 23s! [yyyyyyy:81602]
+</code>
+=== Reason ===
+>A 'soft lockup' is defined as a bug that causes the kernel to loop in kernel mode for more than 20 seconds without giving other tasks a chance to run. The watchdog daemon will send an non-maskable interrupt (NMI) to all CPUs in the system who, in turn, print the stack traces of their currently running tasks.
+-SUSE KB [[https://www.suse.com/support/kb/doc/?id=7017652|7017652]]
+=== Fix ===
+__Solution 1:__
+Restart your system and/ or decrease your CPU load.
+__Solution 2:__
+Increase the time (default 10) before soft lockups are fired.
+<code bash >echo 20 > /proc/sys/kernel/watchdog_thresh</code>
+or
+<code bash>
+echo "kernel.watchdog_thresh=20" > /etc/sysctl.d/99-watchdog_thresh.conf
+sysctl -p  /etc/sysctl.d/99-watchdog_thresh.conf
+</code>
 \\
 \\

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