Summary of Linux knowledge points and Linux knowledge points

Summary of Linux knowledge points and Linux knowledge points

 

1. crontab (1) crontab is executed every 10 seconds

* * * * * /bin/date >>/tmp/date.txt * * * * * sleep 10; /bin/date >>/tmp/date.txt 

(2) You can also use the following methods to express

string            meaning  
------           -------  
@reboot        Run once, at startup.  
@yearly         Run once a year,  " 0 0 1 1 * ".  
@annually      (same as  @yearly)  
@monthly       Run once a month,  " 0 0 1 * * ".  
@weekly        Run once a week,  " 0 0 * * 0 ".  
@daily           Run once a day,  " 0 0 * * * ".  
@midnight      (same as  @daily)  
@hourly         Run once an hour,  " 0 * * * * ”. 

2. Kick the user offline

root@iZ94hgp4s2xZ:~# w  10:15:27 up 1 day, 19:20,  2 users,  load average: 0.00, 0.01, 0.05 USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT jediael  pts/0    218.107.55.252   09:15   31.00s  0.13s  0.13s -bash root     pts/1    218.107.55.252   10:15    1.00s  0.02s  0.00s w root@iZ94hgp4s2xZ:~# pkill -kill -t pts/0 

3. Several bin directories/bin: commands related to boot, including system repairs in single-user mode, such as cp mv bash dmsg grep chmod/sbin: Same as above, generally, root is allowed to use commands such as init iptables lvm/usr/bin: commands unrelated to startup: java tail gcc/usr/sbin: Same as above, generally, the root command useradd usermod/usr/local/bin: when the same software requires a different version but does not want to delete the original version, install the new software here/user/local/sbin: Same as above, general commands used by root 4. view the memory and cpu information in the proc file system cat/proc/cpuinfo cat/proc/meminfo 5. Some Common commands and options

cat /etc/passwd | cut -d ':' -f 1 apt-cache dumpavail | grep  'Package: mysql’ cat /etc/passwd | sort -t ':' -k 3 -n last | cut -d ' ' -f 1 | sort | uniq -c 

 
6. basic steps of disk partitioning (1) create a partition fdisk (2) format the partition mkfs (3) Check the disk and fsck (4) mount the disk
7. apt Common commands (1) install apt-get install scala (2) specify a certain version of apt-get install calla = 2.9.2 (3) delete a software apt-get remove scala (4) search for a software apt-cache search scala