Difference between revisions of "CentOS8 CheatSheet fuer System Administratoren"
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==Journal== | ==Journal== | ||
− | * | + | * Show log since last boot |
− | journalctl - | + | journalctl -b |
− | * | + | * Kernel messages (like dmesg) |
− | journalctl -- | + | journalctl -k |
+ | * Show latest log and wait for changes | ||
+ | journalctl -f | ||
+ | * Reverse output (newest first) | ||
+ | journalctl -r | ||
+ | * Show only errors and worse | ||
+ | journalctl -b -p err | ||
+ | * Filter on time (example) | ||
+ | journalctl --since=2014-06-00 --until="2014-06-07 12:00:00" | ||
+ | * Since yesterday | ||
+ | journalctl --since=yesterday | ||
+ | * Show only log of SERVICE | ||
+ | journalctl -u SERVICE | ||
+ | * Match executable, e.g. dhclient | ||
+ | journalctl /usr/sbin/dhclient | ||
+ | * Match device node, e.g. /dev/sda | ||
+ | journalctl /dev/sda | ||
+ | |||
+ | [[Category:Linux]] | ||
+ | [[Category:ReferenceCards]] | ||
+ | [[Category:Training]] | ||
==Log Files== | ==Log Files== |
Revision as of 15:31, 11 December 2020
Contents
1 SOS Report (Log Bundle)
This collects a log bundle which can be used for later debugging and analyzing.
Start this BEFORE you try to repair or change something, as well do not forget to snapshot/backup System/Application before debugging.
dnf -y install sos sosreport cp -av /var/tmp/sosreport* /root/
1.1 Block Devices (Disks)
- Show block uage of mounted disks
df -hP
- Show inode uage of mounted disks
df -hiP
- show how blockdevices are configured in system
lsblk
- Show memory statistics
free -th
2 Services
- list all service units
systemctl list-unit-files
- show all services in failed state
systemctl --all --state=failed
- show all running services
systemctl --all --state=running
- show detailed service status
systemctl start <svc-name>
- service handing
systemctl [start|stop|restart|enable|disable|mask] <svc-name>
- check if service is enabled to autostart after reboot
systemctl is-enabled <svc-name>
3 Events
3.1 Show last boots
journalctl --list-boots last reboot
3.2 Journal
- Show log since last boot
journalctl -b
- Kernel messages (like dmesg)
journalctl -k
- Show latest log and wait for changes
journalctl -f
- Reverse output (newest first)
journalctl -r
- Show only errors and worse
journalctl -b -p err
- Filter on time (example)
journalctl --since=2014-06-00 --until="2014-06-07 12:00:00"
- Since yesterday
journalctl --since=yesterday
- Show only log of SERVICE
journalctl -u SERVICE
- Match executable, e.g. dhclient
journalctl /usr/sbin/dhclient
- Match device node, e.g. /dev/sda
journalctl /dev/sda
3.3 Log Files
- tail all currently open text files
lsof -F | sed '/^n\//!d;s/^n//;s/ .*//' | sort -u | xargs file | grep ' text$' | cut -d: -f1 | xargs tail -fn0
- tail all files under /var/log
tail -f -n0 /var/log/* /var/log/*/*
4 CentOS 8 Stream migration
CentOS8 will be discontinued by the Red Hat team. All the effort will go into CentOS Stream operating System which is a rolling release of CentOS.
You can directly migrate a CentOS8 into a CentOS8 Stream in place:
dnf install centos-release-stream dnf distro-sync cat /etc/centos-release reboot