E: Пакет 'curl' не имеет кандидата на установку

Я попытался установить curl и получил следующее сообщение об ошибке:

developer@monad:~$ sudo apt install curl
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package curl is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'curl' has no installation candidate  

Что я делаю не так?

Обновление

Когда я выполняю sudo apt update , он говорит:

Hit:1 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:2 http://ppa.launchpad.net/webupd8team/java/ubuntu bionic InRelease        
Get:3 http://ch.archive.ubuntu.com/ubuntu bionic InRelease [242 kB]            
Ign:4 http://dl.google.com/linux/chrome/deb stable InRelease                   
Hit:5 http://archive.canonical.com bionic InRelease                            
Hit:6 http://dl.google.com/linux/chrome/deb stable Release                     
Get:7 http://ch.archive.ubuntu.com/ubuntu bionic-updates InRelease [83.2 kB]
Hit:8 http://ch.archive.ubuntu.com/ubuntu bionic-backports InRelease
Get:9 http://ch.archive.ubuntu.com/ubuntu bionic/main i386 Packages [1'007 kB]
Get:11 http://ch.archive.ubuntu.com/ubuntu bionic/main amd64 Packages [1'019 kB]
Get:12 http://ch.archive.ubuntu.com/ubuntu bionic/main Translation-en [516 kB] 
Get:13 http://ch.archive.ubuntu.com/ubuntu bionic/main amd64 DEP-11 Metadata [477 kB]
Get:14 http://ch.archive.ubuntu.com/ubuntu bionic/main DEP-11 48x48 Icons [118 kB]
Err:14 http://ch.archive.ubuntu.com/ubuntu bionic/main DEP-11 48x48 Icons
  Hash Sum mismatch
  Hashes of expected file:
   - Filesize:118319 [weak]
   - SHA256:72a445c7d354db04d1ffca6f52f7ab66953a3fa889bb66bf6d3210d3ab100f14
   - SHA1:176f580a423a2fcf3e257f0d9a00713e05545a35 [weak]
   - MD5Sum:bdfd4c6a690b2f9d0790443956b327fd [weak]
  Hashes of received file:
   - SHA256:39e0f680c56897c556fd4ce0dbba71e2622b0d1989f2e3fd5ab391d2c7c5c57f
   - SHA1:94e927ca7e5c296674fbed2580f9b34b3eb9f21c [weak]
   - MD5Sum:9b7c8db074b22f5aaba8c8161c204b67 [weak]
   - Filesize:162304 [weak]
  Last modification reported: Thu, 26 Apr 2018 21:24:34 +0000
  Release file created at: Thu, 26 Apr 2018 23:37:48 +0000
Get:15 http://ch.archive.ubuntu.com/ubuntu bionic/main DEP-11 64x64 Icons [245 kB]
Err:15 http://ch.archive.ubuntu.com/ubuntu bionic/main DEP-11 64x64 Icons

Get:16 http://ch.archive.ubuntu.com/ubuntu bionic/restricted i386 Packages [9'156 B]
Get:17 http://ch.archive.ubuntu.com/ubuntu bionic/restricted amd64 Packages [9'184 B]
Get:18 http://ch.archive.ubuntu.com/ubuntu bionic/restricted Translation-en [3'584 B]
Get:19 http://ch.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages [8'570 kB]
Get:20 http://ch.archive.ubuntu.com/ubuntu bionic/universe i386 Packages [8'531 kB]
Get:21 http://ch.archive.ubuntu.com/ubuntu bionic/universe Translation-en [4'941 kB]
Get:22 http://ch.archive.ubuntu.com/ubuntu bionic/universe amd64 DEP-11 Metadata [3'287 kB]
Get:23 http://ch.archive.ubuntu.com/ubuntu bionic/universe DEP-11 48x48 Icons [2'151 kB]
Err:23 http://ch.archive.ubuntu.com/ubuntu bionic/universe DEP-11 48x48 Icons

Get:24 http://ch.archive.ubuntu.com/ubuntu bionic/universe DEP-11 64x64 Icons [8'420 kB]
Err:24 http://ch.archive.ubuntu.com/ubuntu bionic/universe DEP-11 64x64 Icons  

Get:25 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages [52.4 kB]
Get:26 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [52.9 kB]
Get:27 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main Translation-en [18.6 kB]
Get:28 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main amd64 DEP-11 Metadata [6'132 B]
Get:29 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 48x48 Icons [1'968 B]
Err:29 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 48x48 Icons
  File has unexpected size (3584 != 1968). Mirror sync in progress? [IP: 130.59.113.36 80]
  Hashes of expected file:
   - Filesize:1968 [weak]
   - SHA256:cf4c0efefe32dbb80cc114bbcfea0a0839b376b3a226e5d0eec524dfa9a036ba
   - SHA1:6b216ddc4346a7b7ac7952c21dab5b5dc85be71a [weak]
   - MD5Sum:31363305fb0d685cd116efd64c89d0f5 [weak]
  Release file created at: Wed, 16 May 2018 10:13:48 +0000
Get:30 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 64x64 Icons [3'019 B]
Err:30 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 64x64 Icons

Get:31 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe i386 Packages [23.3 kB]
Get:32 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [23.3 kB]
Get:33 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe Translation-en [11.4 kB]
Get:34 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 DEP-11 Metadata [5'360 B]
Get:35 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 48x48 Icons [4'031 B]
Err:35 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 48x48 Icons

Get:36 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 64x64 Icons [12.9 kB]
Err:36 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 64x64 Icons

Get:37 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse amd64 Packages [1'748 B]
Err:37 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse amd64 Packages

Get:38 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse i386 Packages [1'900 B]
Get:39 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse Translation-en [1'236 B]
Fetched 32.3 MB in 7s (4'402 kB/s)                                             
Reading package lists... Done
E: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic/main/dep11/by-hash/SHA256/72a445c7d354db04d1ffca6f52f7ab66953a3fa889bb66bf6d3210d3ab100f14  Hash Sum mismatch
   Hashes of expected file:
    - Filesize:118319 [weak]
    - SHA256:72a445c7d354db04d1ffca6f52f7ab66953a3fa889bb66bf6d3210d3ab100f14
    - SHA1:176f580a423a2fcf3e257f0d9a00713e05545a35 [weak]
    - MD5Sum:bdfd4c6a690b2f9d0790443956b327fd [weak]
   Hashes of received file:
    - SHA256:39e0f680c56897c556fd4ce0dbba71e2622b0d1989f2e3fd5ab391d2c7c5c57f
    - SHA1:94e927ca7e5c296674fbed2580f9b34b3eb9f21c [weak]
    - MD5Sum:9b7c8db074b22f5aaba8c8161c204b67 [weak]
    - Filesize:162304 [weak]
   Last modification reported: Thu, 26 Apr 2018 21:24:34 +0000
   Release file created at: Thu, 26 Apr 2018 23:37:48 +0000
E: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic/main/dep11/by-hash/SHA256/57f27cd53b92604cbf5c549382eec53d66ef2500fbdd54692688fd3675786aeb  
E: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic/universe/dep11/by-hash/SHA256/44352c8652af9c9071b7cc7a035de3cd55b012e1df7291644bf9b99fd9dffd5a  
W: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic/universe/dep11/by-hash/SHA256/ad41f363b444b3cec5ab94623ea0a5b42a7ea0165e70af3aabf14f244bdbd9eb  
E: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic-updates/main/dep11/by-hash/SHA256/cf4c0efefe32dbb80cc114bbcfea0a0839b376b3a226e5d0eec524dfa9a036ba  File has unexpected size (3584 != 1968). Mirror sync in progress? [IP: 130.59.113.36 80]
   Hashes of expected file:
    - Filesize:1968 [weak]
    - SHA256:cf4c0efefe32dbb80cc114bbcfea0a0839b376b3a226e5d0eec524dfa9a036ba
    - SHA1:6b216ddc4346a7b7ac7952c21dab5b5dc85be71a [weak]
    - MD5Sum:31363305fb0d685cd116efd64c89d0f5 [weak]
   Release file created at: Wed, 16 May 2018 10:13:48 +0000
E: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic-updates/main/dep11/by-hash/SHA256/2b149a45789655d141ab257c7d7cb5d23ade57a6cc37b50bdb3b809889038b8c  
E: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic-updates/universe/dep11/by-hash/SHA256/3f6762646dd674ed60d5ed3c1079f9ece9d61077d3becb1366a643f745cf4fb6  
E: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic-updates/universe/dep11/by-hash/SHA256/ed5270073a7d5a426dd1c90da502d9ea4f47170ea93a26b073eca3a1f2729722  
E: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/bionic-updates/multiverse/binary-amd64/by-hash/SHA256/bbd2dc9fb47a4a186dfa72cb47b3fd98c5c8bf6cc2f643278f60e466a395858f  
W: Some index files failed to download. They have been ignored, or old ones used instead.