Difference between revisions of "CentOS8 CheatSheet fuer System Administratoren"
Jump to navigation
Jump to search
Line 111: | Line 111: | ||
− | = | + | =Debugging= |
+ | ==strace examples (process tracing)== | ||
+ | strace -ff -e trace=write -e write=1,2 -p SOME_PID | ||
+ | strace -e open ls | ||
+ | strace -e trace=open,read ls /home | ||
+ | strace -o output.txt ls | ||
+ | strace -f -p 1725 -o firefox_trace.txt # f: follow process | ||
+ | strace -t -e open ls /home #timestamp | ||
+ | strace -c ls /home # statistics | ||
+ | strace -f -t -e trace=file systemctl restart SuSEfirewall2 2>&1 | grep open | cut -d'"' -f2 | ||
+ | |||
==SOS Report (Log Bundle)== | ==SOS Report (Log Bundle)== | ||
This collects a log bundle which can be used for later debugging and analyzing. <br> | This collects a log bundle which can be used for later debugging and analyzing. <br> | ||
Line 118: | Line 128: | ||
sosreport | sosreport | ||
cp -av /var/tmp/sosreport* /root/ | cp -av /var/tmp/sosreport* /root/ | ||
+ | |||
+ | =This and That= | ||
==CentOS 8 Core to Stream migration== | ==CentOS 8 Core to Stream migration== |
Revision as of 07:46, 14 December 2020
Contents
1 System
1.1 Hardware
- Show hardware details
lshw
- show bios hardware details
dmidecode
1.2 Disk/Filesystem
- Show block uage of mounted disks
df -hP
- Show inode uage of mounted disks
df -hiP
- show how blockdevices are configured in system
lsblk
- get 10 biggest files in current dir
du -sm * .[^\.]* | sort -n | tail
- use ncdu to find large files
dnf -y install epel-release dnf config-manager --enable epel dnf -y install ncdu ncdu -x / #replace / with needed mountpoint
1.3 Memory
- Show memory statistics
free -th
- Top provides memory information as well
top
1.4 CPU
- show system load (1m, 5m, 15m)
w
- detailed realtime statictics of procs, memory, swap, io, system, cpu
vmstat 1
1.5 Processes
- show processes with tree
ps -f fax
- detailed process information
ps -faxo ruser,ppid,pid,rss,vsz,pcpu,tty,args
1.6 Debugging Tools
- dstat performance monitoring
dnf -y install pcp-system-tools dstat -af dstat -cdngy dstat -f -M time,cpu,net,disk,sys,swap,page,load,proc,topcpu --output $(date '+%Y.%m.%d-%H.%M')-dstat.csv dstat -cdngymsp --lock --tcp --output $(date '+%Y.%m.%d-%H.%M')-dstat.csv
2 Services
- list all services
systemctl list-units --type service
- List failed services on boot
systemctl --failed
- show all running services
systemctl --all --state=running
- show detailed service status
systemctl status <svc-name>
- most common service handling
systemctl [start|stop|restart|status|enable|disable|mask] <svc-name>
- check if service is enabled to autostart after reboot
systemctl is-enabled <svc-name>
3 Events
3.1 Show last boots
journalctl --list-boots last reboot
3.2 Journal
- Show log since last boot
journalctl -b
- Kernel messages (like dmesg)
journalctl -k
- Show latest log and wait for changes
journalctl -f
- Reverse output (newest first)
journalctl -r
- Show only errors and worse
journalctl -b -p err
- Filter on time (example)
journalctl --since=2014-06-00 --until="2014-06-07 12:00:00"
- Since yesterday
journalctl --since=yesterday
- Show only log of SERVICE
journalctl -u SERVICE
- Match executable, e.g. dhclient
journalctl /usr/sbin/dhclient
- Match device node, e.g. /dev/sda
journalctl /dev/sda
3.3 Log Files
- tail all currently open text files
lsof -F | sed '/^n\//!d;s/^n//;s/ .*//' | sort -u | xargs file | grep ' text$' | cut -d: -f1 | xargs tail -fn0
- tail all files under /var/log
tail -f -n0 /var/log/* /var/log/*/*
4 Debugging
4.1 strace examples (process tracing)
strace -ff -e trace=write -e write=1,2 -p SOME_PID strace -e open ls strace -e trace=open,read ls /home strace -o output.txt ls strace -f -p 1725 -o firefox_trace.txt # f: follow process strace -t -e open ls /home #timestamp strace -c ls /home # statistics strace -f -t -e trace=file systemctl restart SuSEfirewall2 2>&1 | grep open | cut -d'"' -f2
4.2 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/
5 This and That
5.1 CentOS 8 Core to 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.
This is not a replacement for CentOS Core!!! Even if Red Hat will rename CentOS Stream to CentOS later on.
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