bash

How to Increase Bash History Size

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Some valuable or complex commands may not be able to keep in your mind constantly when you need them. In this moment, you can leverage the command history to recall them. But as time goes by, you could lose them due to the size limitation of command history. The history always keep the most recent […]
Linux

How to Resolve RTNETLINK answers: Invalid argument Error adding default gateway

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RTNETLINK answers: Invalid argument When I restarted the newly configured network interface, it returned error rtnetlink answers: invalid argument like the following: [root@test ~]# service network restart … RTNETLINK answers: Invalid argument Error adding default gateway … Please check the gateway that you just set.[root@test ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth2 … GATEWAY=192.168.25.1 If you were sure about […]
Linux

How to Add a Second IP Address to Current NIC

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Let’s see current setting of all interfaces.[root@test ~]# ifconfigeth0      Link encap:Ethernet  HWaddr 00:0C:29:D8:AE:2D          inet addr:10.0.0.152  Bcast:10.0.0.255  Mask:255.255.255.0          inet6 addr: fe80::20c:29ff:fed8:ae2d/64 Scope:Link          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1          RX packets:113 errors:0 dropped:0 overruns:0 frame:0          […]
AIX

How to Compare Contents of Two Directories

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After you copied one directory to another like this:$ cp -rp /path/to/source/directory /path/to/target/or mirrored the source directory to the target one.$ rsync -av /path/to/source/directory/ /path/to/target/directory/You might want to confirm your job is done. Let’s see what we can compare between the two.Total Size$ du -sb /path/to/source/directory; du -sb /path/to/target/directorydu usually returns a proximate result which […]
Firewalld

How to Install Newest LAMP on CentOS 7.2 Minimal (4/4) – Configure Daemons and Firewall

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Configure MySQL Daemon [root@test ~]# systemctl status mysqld.service â— mysqld.service – MySQL Server    Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)    Active: active (running) since Tue 2016-03-22 20:40:37 EDT; 5min ago   Process: 2158 ExecStart=/usr/sbin/mysqld –daemonize –pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)   Process: 1620 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)  Main PID: 2814 (mysqld)    CGroup: /system.slice/mysqld.service   […]
Linux

The Size Limit for Legacy Tar to Accomodate

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A quote from wikipedia:Numeric values are encoded in octal numbers using ASCII digits, with leading zeroes. For historical reasons, a final NUL or space character should also be used. Thus although there are 12 bytes reserved for storing the file size, only 11 octal digits can be stored. This gives a maximum file size of […]
Linux

How to Authorize Users to Use Crontab

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Check /etc/cron.deny first If there’s no /etc/cron.allow in your system, please make sure the user (e.g. oracle) that we would like to authorize it here does not show in /etc/cron.deny. /etc/cron.allow takes priority over /etc/cron.deny If you want a positive listing, you can create and add oracle to /etc/cron.allow which will suppress /etc/cron.deny. Create /etc/cron.allow […]